9.3 – Physiology of the Heart
In order for the heart to do its job of pumping blood to the lungs and to the body, nutrients and oxygen must be supplied to the cells of the heart. The heart also needs to coordinate its contractions so that all parts are working together to pump blood effectively. To understand how all of this works together to give the heart its ability to pump blood, we will examine three interdependent aspects of heart function.
- Circulation through the heart: blood is pumped by the heart in order to provide oxygen and nutrients to every cell in the body.
- The heart as an organ (coronary blood supply): the heart is an organ, made of cells and tissues which require their own blood supply.
- The heart’s electrical conduction system: the heart is able to independently generate and transmit instructions to the myocardium, in order to make it contract and pump the blood.
1. Circulation Through the Heart: The Heart as a Pump
The heart pumps blood to two distinct but linked circulatory systems called the pulmonary and systemic circuits. The pulmonary circuit transports blood to and from the lungs, where it picks up oxygen and drops off carbon dioxide. The systemic circuit transports freshly oxygenated blood to virtually all of the tissues of the body and returns relatively deoxygenated blood and carbon dioxide to the heart to be sent back to the pulmonary circulation.
Did You Know?
- Blood that is carrying carbon dioxide and waste products from the body tissues is returned to the right atrium via the superior vena cava and the inferior vena cava.
- From the right atrium, the deoxygenated blood moves through the tricuspid valve into the right ventricle.
- The right ventricle pumps deoxygenated blood through the pulmonary valve into the pulmonary trunk, which splits into the right and left pulmonary arteries, leading toward the lungs. These arteries branch many times before reaching the pulmonary capillaries, where gas exchange occurs: carbon dioxide exits the blood and oxygen enters. The pulmonary arteries are the only arteries in the postnatal body that carry deoxygenated blood. Did you notice that they are often coloured blue on diagrams of the heart?
- Freshly oxygenated blood returns from the lungs to the left atrium via the pulmonary veins. These veins are the only postnatal veins in the body that carry highly oxygenated blood and are often coloured red on heart images.
- From the left atrium, the blood moves through the mitral valve into the left ventricle.
- The left ventricle pumps blood through the aortic valve, into the aorta, delivering blood to all parts of the body.
Concept Check 1
- On Figure 9.3 below, use your finger to trace the pathway of blood flowing through the right side of the heart, naming each each of the following structures as you encounter them: superior and inferior venae cavae, right atrium, tricuspid valve, right ventricle, pulmonary valve, right and left pulmonary arteries.
- Suggest what would happen if the aorta experienced a blockage or constriction.
Watch The Heart, Part 2 – Heart Throbs: Crash Course Anatomy & Physiology #26 (9:30 min) on YouTube
Media 9.2: CrashCourse. (2015, July 13). The heart, part 2 – Heart throbs: Crash Course anatomy & Pphysiology #26 [Video]. YouTube. https://youtu.be/FLBMwcvOaEo
Concept Check 4
- On the image (Figure 9.6) above, trace the electrical impulse generated by the heart’s pacemaker (the sinoatrial node, or SA node) through the rest of the conduction system, including the atrioventricular (AV) node, the atrioventricular bundle (bundle of His), the right and left bundle branches, and the Purkinje fibers.
We can detect and record the electrical activity of the heart’s conduction system using an electrocardiogram (ECG or EKG). Figure 9.7 shows the electrical impulse originating in the SA node (step 2) and travelling through the heart’s conduction system, allowing the heart to complete one cardiac cycle. Each waveform on the ECG tracing represents electricity moving through and affecting a different part of the heart. Did you notice that the AV valves close when the electrical impulse reaches the ventricles, just before systole occurs?
Heart Medical Terms and Abbbreviations
Cardiovascular System – Heart Terms Not Easily Broken Down
Cardiovascular System – Heart Terms Not Easily Broken Down (Text Version)
Practice the following cardiovascular system words by breaking into word parts and pronouncing.
- arrhythmia
- deviation in the normal pattern (rhythmn) of a heartbeat
- congenital
- present at birth
- stethoscope
- An instrument used to hear heart and lung sounds
- aneurysm
- localized dilation of the wall of a blood vessel
- diastole
- Phase in the cardiac cycle where heart muscles relax allowing the chambers to fill with blood.
- bruit
- abnormal blowing, swishing heart sound heard on auscultation
- syncope
- brief lapse in consciousness (faint)
- auscultation
- listening to a patient’s heart sounds
- occlude
- block or close tightly
- sphygmomanometer
- instrument used to measure blood pressure
- diaphoresis
- profuse (excessive) sweating
- myocardial infarction (MI)
- heart attack, caused by lack of blood flow and oxygen to the heart
- systole
- Phase in cardiac cycle when ventricles contract and eject blood
Activity source: Cardiovascular System – Heart not easily broken down by Kimberlee Carter, from Building a Medical Terminology Foundation by Kimberlee Carter and Marie Rutherford, licensed under CC BY- 4.0. /Text version added.
Heart Abbreviations
Many terms and phrases related to the cardiovascular system- heart are abbreviated.
Learn these common abbreviations by expanding the list below.
Cardiovascular System – Heart Common Abbreviations
- ACS (acute coronary syndrome)
- AFib (atrial fibrillation)
- AV (atrioventricular)
- BP (blood pressure)
- CABG (coronary artery bypass graft)
- CAD (coronary artery disease)
- CCU (coronary care unit, cardiac care unit)
- CPR (cardiopulmonary resuscitation)
- DVT (deep vein thrombosis)
- ECG, EKG (electrocardiogram)
- ECHO (echocardiogram)
- HF (Heart Failure)
- HHD (hypertensive heart disease)
- HTN (hypertension)
- IV (intravenous)
- MI (Myocardial Infarction)
- PAD (peripheral artery disease)
- PTCA (percutaneous tranluminal coronary angioplasty)
- SPECT (single-photon emission computed tomography)
- TEE (transesophageal echocardiogram)
Activity source: Cardiovascular System – Heart Common Abbreviations by Kimberlee Carter, from Building a Medical Terminology Foundation, licensed under CC BY 4.0./ Text version added.
Image Descriptions
Figure 9.3 image description: This diagram shows the network of blood vessels in the lungs. Labels read (from top, clockwise (left-side of the body): aortic arch, pulmonary trunk, left lung, left pulmonary arteries, left pulmonary vein, pulmonary capillaries, descending aorta, (right side of body) inferior vena cava, right pulmonary veins, right pulmonary arteries, right lung, superior vena cava, ascending aorta. [Return to Figure 9.3].
Figure 9.4 image description: The top panel shows the human heart with the arteries and veins labeled (from top, clockwise): aorta, left pulmonary arteries, pulmonary trunk, left atrium, left pulmonary veins, aortic semilunar valve, mitral valve, left ventricle, inferior vena cava, right ventricle, tricuspid valve, right atrium, pulmonary semilunar valve, right pulmonary veins, right pulmonary arteries, superior vena cava. The bottom panel shows a rough map of the the human circulatory system. Labels read (from top, clockwise): systemic capillaries of upper body, systemic arteries to upper body, pulmonary trunk, left atrium, left ventricle, systemic arteries to lower body, systemic capillaries of lower body, systemic veins from lower body, right ventricle, right atrium, pulmonary capillaries in lungs, systemic veins from upper body. [Return to Figure 9.4].
Figure 9.5 image description: The top panel of this figure shows the anterior view of the heart while the bottom panel shows the posterior view of the heart. The different blood vessels are labeled. Anterior view labels (from top of diagram, clockwise): left coronary artery, pulmonary trunk, circumflex artery, anterior interventricular artery, great cardiac vein, small cardiac vein, anterior cardiac veins, atrial arteries, right atrium, right coronary artery, ascending aorta, aortic arch. Posterior view labels (from top of diagram, clockwise): coronary sinus, small cardiac vein, right coronary artery, marginal artery, middle cardiac vein, posterior cardiac vein, posterior interventricular artery, marginal artery, great cardiac vein, circumflex artery. [Return to Figure 9.5].
Figure 9.6 image description: This image shows the anterior view of the frontal section of the heart with the major parts labeled. Labels read (from top of diagram, clockwise) arch of aorta, Bachman’s bundle, atrioventricular bundle (bundle of His), left ventricle, right and left bundle branches, Purkinje fibers, right ventricle, right atrium, posterior intermodal, middle intermodal, atrioventricular node, anterior intermodal, Sinoatrial node. [Return to Figure 9.6].
Figure 9.7 image description: This diagram shows the six different stages of heart contraction and relaxation along with the stages in the QT cycle. [Return to Figure 9.7].
Attribution
Except where otherwise noted, this chapter is adapted from “Cardiovascular System – Heart” in Building a Medical Terminology Foundation by Kimberlee Carter and Marie Rutherford, licensed under CC BY 4.0. / A derivative of Betts et al., which can be accessed for free from Anatomy and Physiology (OpenStax). Adaptations: dividing Cardiovascular System – Heart chapter content into sub-chapters.
One of the two largest veins in the body. It carries deoxygenated blood from the head and upper extremities back to the heart.
One of the two largest veins in the body. It carries deoxygenated blood from the torso and legs back to the heart.
very large artery referred to as a trunk, a term indicating that the vessel gives rise to several smaller arteries
Atrioventricular valves: mitral (bicuspid) valve allows blood to flow from left atrium to left ventricle, tricuspid valve allows blood to flow from right atrium to right ventricle


Chapter 2
Preoperative Case Study Answers
1. What information do you need to know or gather about this client before surgery occurs? Why?
- Last time aspirin or Tylenol was taken (bleeding consideration).
- Consent needed to be explained again, by the surgeon, whether surgery is vaginal or abdominal (Client isn’t clear about approach for surgery).
- Prior problems with surgery or anesthesia for client or family members (Assesses malignant hyperthermia risk).
- Support system of a friend or family members who can help during recovery and whether they are present (Second person to listen to postoperative instructions to later coach client/monitor and assist client in the first 24 hours after surgery).
- Full medication reconciliation to identify if any medications would interact with the anesthesia and if they were taken within a time frame of the surgery.
- Thorough health assessment to consider risk factors (Hypoventilation, renal excretion of medications, etc.).
- Client’s normal blood pressure/pulse range (Monitor hemodynamic changes related to surgery).
- Height/weight (Anesthesia dosing).
- Allergies (Drug interactions).
- Preexisting infections, medical conditions, and H&P to identify any potential for increased surgical risk.
- Support system at home when discharged.
- Electrocardiogram for client over 40 years old (Identify cardiac risk) and preoperative labs such as CBC and BMP to examine bleeding risk, renal function, etc.
2. Describe the client teaching needed. How would you prioritize teaching needs?
- Priority consideration is clarifying the procedure for the client to ensure informed consent.
- Need for surgeon to explain to the client the procedure; at this point the nurse has determined the consent hasn’t been obtained as the client has questions and doesn’t understand the type of surgery being performed.
- To assess understanding, have the client reiterate the procedure to determine understanding using no leading language, “Ms. Smith, can you tell me why you are at the hospital today?”
Additional teaching related to the procedure may include the following:
-
- Teaching about pain management, expected blood loss, infection signs/risk, etc.
- Teaching the importance of coughing and deep breathing after surgery, as well as early ambulation and leg exercises.
- Client also demonstrates sign of psychological discomfort related to the procedure. As a result, the preoperative nurse should take the following actions:
- Anesthesiologist can provide additional teaching/reassurance regarding fear of “going under.”
- Anesthesiologist may order preoperative anxiety medication.
- Nurse and members of surgical team should continue to reinforce what to expect before, during, and after the surgery (incisions, dressings, wound care, etc.).
3. What lab tests and other diagnostic tests should be completed? Why?
- RBC, hemoglobin, hematocrit, and platelet levels due to prior heavy bleeding.
- WBC to determine if WBCs are elevated, which may indicate underlying infection and potentially delayed surgery.
- Blood glucose (if diabetic) to know if client will need medications during or before surgery to keep blood sugar stable.
- Blood type needed (in case the client needs blood transfusion with expected blood loss).
4. Is there any information that should be shared with the surgeon or anesthesiologist?
- Client has never had surgery (risk for malignant hyperthermia) and no known reaction to anesthesia.
- The client is unclear about aspects of her surgery and needs further explanation. She is anxious and afraid.
5. What interventions can be used to reduce the client’s anxiety?
- Answer any questions
- Relaxation techniques
- Distraction
- Family present
- Medications (e.g., Midazolam [Versed], Lorazepam [Ativan])
- Explain what will happen after surgery
- Explain what she will likely be feeling
- Explain what she can do to decrease pain
6. Based upon the information provided, what type of surgery is being described?
- The surgery would be classified as curative to resolve health problems. It would be considered a major surgery with general anesthesia.
- Hysterectomy is a surgical operation to remove all or part of the uterus. The surgery can be identified as abdominal, vaginal, or laparoscopic.
7. What medications might be given preoperatively to this client and why?
- The medications that might be given preoperatively include Midazolam to assist with relaxation, Atropine (if anesthesiologist prefers) to help dry secretions, Famotidine to help with controlling potential acid reflux with surgery, and Ondansetron if client experiences nausea.
8. What if this client were 88 years old. How should preoperative care be modified to meet the needs of an older adult?
- Making sure a family member is with the client.
- Identifying the client’s decision-making capacity and identified/activated power of attorney for health care
- Understanding the different reactions to anesthesia and medications.
- Knowing that the elderly are at a higher risk for fluid imbalance, leading to confusion and postural hypotension.
- Understanding that weakened respiratory muscles can lead to collapsed lungs and impaired respiratory pattern.
9. What risks are more likely with an older adult?
- Delayed/ impaired healing
- Increased risk of infection
- Risk for falls
- Less able to adjust to the stress of surgery
- More prone to postural hypotension
- Potential complications with the lungs
- Difficulty maintaining blood pressure
- Need for more help with after-surgery medications
- Increased risk for aspiration
- Diminished hearing
- Forgetfulness -> impaired ability to retain information
- Decreased liver/kidney function -> may need reduced dosage of narcotics/sedatives
- Adverse drug responses -> fat soluble drugs have longer duration of action
- Hypoventilation due to decreased lung expansion and weakened respiratory muscles
- Skin breakdown due to decreased mobility
All of the answers to the interactive element are found within the element.


2.4 Today’s Recreation, Park, And Leisure Services
Overview of Recreation, Park, And Leisure Services
The realm of recreation, park, and leisure services weaves together threads of well-being, community, and enrichment in modern society. These services stand as sanctuaries of respite, spaces for connection, and avenues for personal growth as we navigate the fast-paced currents of contemporary life. This section offers a panoramic glimpse into the diverse and vibrant landscape of recreation, park, and leisure services that shape our present-day experiences, foster social cohesion, and contribute to the vitality of communities.
The services encompassed in modern recreation, park, and leisure services cater to a vast spectrum of interests and aspirations, from the heart of bustling cities to the serenity of natural landscapes. Beyond the realm of mere leisure, these offerings contribute to physical vitality, mental rejuvenation, and the strengthening of bonds within communities. The world of recreation and leisure services holds something for everyone whether it is a leisurely stroll through a local park, an exhilarating outdoor adventure, or a culturally enriching community event.
Section 2.4 moves us from historical antecedents of recreation, park, and leisure and into the myriad dimensions that constitute today’s recreation, park, and leisure services. We explore the economic significance of these activities, tracing their contributions to national and state economies. Through the lens of participation statistics, we witness the widespread engagement in various recreational pursuits and the growing allure of outdoor adventure travel. Moreover, we examine how the skills and insights garnered from the hospitality and tourism industries seamlessly integrate into park management roles, enhancing visitor experiences and community engagement.
Modern Recreation: A Period of Engagement and Growth
Recreation is more than a source of enjoyment and relaxation. Recreation has become a significant contributor to economies, a driving force for domestic travel, and a catalyst for fostering physical and mental well-being. It becomes evident that recreation’s multifaceted appeal has transformed it into a dynamic and influential facet of modern society.
Recreation has emerged as a formidable economic engine, generating substantial contributions to national and state economies. Recreation accounted for a staggering $454 billion in the United States in 2021. This constitutes approximately 1.9% of the nation’s gross domestic product (GDP) for 2021 (Bureau of Economic Analysis [BEA], 2022). This robust economic impact is not limited to the federal level.
Outdoor recreation's share of GDP ranged from 4.8% in Hawaii to 1.3% in states like New York and Connecticut at the state level in 2021 (BEA, 2022). This economic clout underscores the fact that recreation is not merely a leisure pursuit but a critical industry that creates jobs, fuels consumer spending, and sustains local communities. Participation is so strong in recreation that it is a mega trend in modern society.
The allure of recreation activities resonates deeply with individuals from all walks of life. A remarkable 54% of Americans aged 6 and above actively participated in at least one outdoor recreation activity in 2021 (Outdoor Foundation, 2022). This impressive engagement signifies the broad appeal of outdoor experiences as a means of rejuvenating mind, body, and spirit. The top five activities (i.e., running, hiking, fishing, biking, and camping) paint a vivid picture of the diverse range of pursuits that capture the interest of modern-day enthusiasts.
Outdoor recreation is driving domestic travel and adventure. This makes the overlap between recreation, hospitality, and tourism pronounced. The compelling draw of recreation activities has played an instrumental role in the surging popularity of domestic travel within the United States (Nationwide, 2024). Outdoor adventure travel, in particular, has experienced an exponential rise in prominence. This growth signals a growing preference for experiential and nature-centric escapades. Individuals are seeking out destinations that offer opportunities for outdoor pursuits, from embarking on epic hiking trails to camping beneath starlit skies. The call of the wild, coupled with the desire to disconnect from the demands of modern life, has ignited a renewed passion for embarking on journeys that center around outdoor engagement.
The landscape of modern recreation services has evolved into a thriving and transformative force that intersects with economics, travel, and lifestyle choices. The economic significance of recreation cannot be understated, as it contributes billions to national and state economies. The participation of over half of the American population in outdoor recreation activities underscores the widespread appeal of these pursuits as avenues for holistic well-being. Moreover, the surge in outdoor adventure travel speaks to the contemporary desire for immersive and rejuvenating experiences that forge connections with nature and kindle a sense of exploration. In essence, understanding the role of recreation today entails recognizing its multifaceted impact on society, the economy, and the individual pursuit of joy and fulfillment.
Modern Parks: A Global Exploration of Preservation and Enjoyment
Parks stand as sanctuaries of nature’s beauty, cultural heritage, and shared human experiences. These expansive spaces, carefully preserved and thoughtfully curated, serve as living testimonies to our collective appreciation for the outdoors, our history, and our innate need for connection with the natural world. In this section, we embark on a journey to understand the multifaceted significance of parks today, taking a global perspective that spans national, state, and city levels.
Modern recreation, park, and leisure services are intricately woven with the threads of national, state, and city parks. From the towering majesty of national parks to the intimate charm of city parks, these spaces celebrate nature’s beauty, nurture community bonds, and enrich the lives of millions. As we continue to navigate the complexities of the modern world, these parks stand as testaments to our shared reverence for the outdoors, our heritage, and the enduring power of natural and cultural landscapes.
National Parks: Guardians of Natural and Cultural Treasures
A pivotal moment in the history of parks occurred on August 25, 1916, with the signing of the National Park Service Organic Act, commonly known as the “Organic Act,” by President Woodrow Wilson. This landmark legislation marked the inception of the National Park Service (NPS), a federal agency entrusted with the stewardship and preservation of the United States’ most cherished landscapes and historic landmarks. As a custodian of national parks and monuments, the NPS shoulders the responsibility of safeguarding the country’s natural wonders and cultural heritage, ensuring that they remain accessible and unspoiled for generations to come.
Today, the U.S. National Park system has blossomed into a cornerstone of the nation’s tourism industry, welcoming an astounding 300 million visitors annually (NPS, 2023b). Among its crown jewels, the Great Smoky Mountains National Park stands as the most frequented destination, having hosted 12.9 million visitors in 2022 (NPS, 2023a). With an annual budget of approximately $4 billion, the NPS oversees a diverse array of 424 national park sites, collectively spanning a staggering 84 million acres (NPS, 2024b). Among these, the monumental Wrangell-St. Elias National Park and Preserve in Alaska emerges as a titan, covering an expansive 13.2 million acres, equivalent to around 16% of the entire national park system (National Park Foundation, n.d.). On the opposite end of the spectrum, the diminutive Thaddeus Kosciuszko National Memorial in Pennsylvania claims the title of the smallest site, occupying a mere 0.02 acres (Errick, 2014). The preservation of these treasures is not only an ode to the country’s heritage but also a testament to the value placed on natural beauty and ecological diversity.
A Legacy of Conservation and Forest Management: The U.S. Forest Service
The journey towards preserving and managing the nation’s forests, a vital thread in the fabric of recreation and leisure services, traces its origins to the late 19th century. In 1876, Congress birthed the office of Special Agent within the U.S. Department of Agriculture, charged with evaluating the quality and condition of the nation’s forests (Forest Service, n.d.). This momentous step laid the foundation for the subsequent creation of the Division of Forestry in 1881. A significant leap forward came with the Forest Reserve Act of 1891 (also known as the General Revision Act or the Land Revision Act), granting the President the authority to designate public lands in the West as “forest reserves,” a precursor to today’s national forests.
The stewardship of these reserves shifted in 1905 when President Theodore Roosevelt transferred their management to the newly formed Forest Service under the U.S. Department of Agriculture (Forest Service, n.d.). Gifford Pinchot, a visionary conservationist, was entrusted with its leadership. Pinchot’s tenure marked a watershed moment as he championed a decentralized structure that empowered civil servants to make conservation decisions at the local level. This strategic approach revolutionized forest management, weaving a seamless tapestry of sustainable practices and protection, thereby nurturing the delicate balance between human interaction and the preservation of pristine landscapes.
The exploration of parks today beckons us to delve into the intricate tapestry of preservation, enjoyment, and stewardship that weaves together the global landscape of national, state, and city parks. From the towering expanses of national parks to the intricate urban oases of city parks, these spaces stand as testimony to humanity’s profound connection with nature and heritage. The tales they tell transcend borders, inviting us to embark on a journey that stretches beyond time and space, nurturing the soul, and enriching our shared narrative.
Modern State Parks: Celebrating Local Treasures
State parks, akin to their national counterparts, have evolved into vital components of contemporary recreation and leisure services. These cherished spaces, often spanning picturesque landscapes, historical sites, and unique ecosystems, offer a closer-to-home haven for outdoor enthusiasts and community gatherings. State governments across the United States have recognized the significance of preserving these local treasures, not only for their natural beauty but also as magnets for tourism and community engagement.
In recent years, state parks have gained prominence for their role in fostering both recreation and conservation. These parks play a pivotal part in enhancing the quality of life for residents while offering visitors a chance to experience the great outdoors. According to the National Association of State Park Directors, state parks collectively welcomed over 813 million visitors in 2020 (America’s State Parks, n.d.). The allure of state parks is underscored by their accessibility, as they cater to diverse interests, from hiking and camping to bird-watching and picnicking.
City Parks: Breathing Spaces in Urban Landscapes
Amidst the bustling concrete jungles of urban landscapes, city parks emerge as verdant sanctuaries, serving as essential breathing spaces for residents and visitors alike. These oases of greenery offer a respite from the hustle and bustle of city life, providing a canvas for relaxation, recreation, and community cohesion. City parks have the unique ability to foster a sense of unity and belonging, forging connections between diverse individuals who converge to enjoy their serene offerings.
As cities continue to evolve and expand, the importance of city parks becomes increasingly evident. These green spaces are essential for maintaining the ecological balance of urban environments, offering a haven for local flora and fauna. Additionally, they serve as venues for cultural events, art installations, and social gatherings, weaving a tapestry of vibrant experiences. According to the Trust for Public Land (n.d.), two-thirds of Americans live within a 10-minute walk of a park, underscoring the accessibility and centrality of city parks to modern life.
Modern Leisure: Paradigms of Leisure in 21st Century Society
Leisure has taken a different path than recreation or parks as it moved into modern society. Most of leisure’s trends exist in a more academic than applied fashion.
From the 1980s onward, critical approaches also developed in leisure studies (Parr & Schmalz, 2019). Critical theorists examined how power, domination, and social structures shaped leisure opportunities. Feminist leisure scholars highlighted gender differences in leisure. Postmodern perspectives looked at leisure subjectivities and the body. Critical race theory and postcolonialism were applied to analyze ethnicity and race.
More recent trends in leisure studies reflect changing social contexts. Some examples include:
- Examining impacts of technology and digital media on recreation, travel, and tourism
- Understanding relationships between leisure and health wellbeing
- Exploring the role of urban green spaces, community gardens, parks for quality of life
- Analyzing leisure across the lifespan from childhood play to retirement
- Investigating lifestyle sports, serious leisure subcultures, and extreme sports
- Applying positive psychology and happiness research to leisure experiences
- Developing leisure education and programming for underserved groups
- Promoting social justice, inclusion, and universal access to recreation
- Focusing on sustainability, climate change, environmentalism and outdoor recreation
- Adding global and cross-cultural perspectives on leisure meanings and activities
Academically, leisure studies is an interdisciplinary field, with scholarly contributions coming from diverse social science and humanities backgrounds. Leisure research appears in journals specific to the field, like Leisure Sciences, Leisure Studies, Leisure/Loisir, Journal of Leisure Research, and others. But leisure scholarship also crosses over into publications in fields like tourism, sports studies, parks and recreation, education, gerontology, youth studies, sociology, psychology, geography, planning, and more.
The future directions of leisure studies remain open and flexible. The nature of leisure itself continues to evolve along with wider societal changes. As patterns of work, technology use, urbanization, travel, and lifestyle preferences transform in the 21st century, academics will keep exploring the meaning and role of leisure in contemporary life. The interdisciplinary tools and critical lenses of leisure studies can provide useful insights on recreation, quality of life, human development, family and community, equity and social justice, sustainability, globalization, and more. With its multifaceted frameworks, leisure studies is poised to remain a vibrant and relevant field.
Types Of Recreational Activities And Programs
Recreational activities take diverse forms, ranging from casual leisure pursuits to more intense and skill-based endeavors. They can be categorized in various ways – by environment, physical intensity, necessary equipment, social interaction, and more.
Outdoor recreation remains a hugely popular category, taking advantage of natural settings. This includes land-based activities like hiking, backpacking, orienteering, mountain biking, rock climbing, horseback riding, and multi-sport adventures. Water-based outdoor recreation includes swimming, snorkeling, scuba diving, surfing, whitewater rafting, kayaking, canoeing, stand-up paddleboarding, water skiing, wakeboarding, sailing, and motorboating. Snow sports are also vibrant recreational activities, including downhill skiing, snowboarding, cross-country skiing, snowshoeing, and snowmobiling.
Outdoor recreation relies on extensive public park systems, wilderness preserves, forests, mountains, rivers, lakes, oceans, and other natural environments. Programming often centers on environmental education, skill-building, wellness, and conservation. Guided activities like naturalist hikes, stargazing, birdwatching tours, and campfire talks enhance visitors’ connections with nature.
Sports and fitness are another major recreation category. This covers casual pickup games, intramural leagues, youth and adult competitive leagues, clinics, and tournaments across a spectrum of sports – basketball, baseball, soccer, football, tennis, volleyball, disc golf, and more. Fitness-oriented programming spans classes and training programs focused on cardiovascular health, strength, flexibility, dance, mindfulness, and holistic wellbeing. Community recreation centers are major providers of sports and fitness programming.
The arts offer enriching recreational programming. Options include visual arts classes and workshops in painting, photography, ceramics, jewelry-making, woodworking, and other media. Performing arts programming covers music lessons, choir and musical ensembles, dance classes, and theater workshops leading to productions. Literary arts programs involve writing seminars, poetry slams, storytelling events, and book clubs. Arts festivals and public art installations further engage local communities.
Many municipalities offer targeted recreation programming for youth, older adults, and people with disabilities. Youth programming provides supervised afterschool and summer activities to enrich education and social growth. Senior programming ranges from crafts classes to fitness activities tailored for older adults. Adaptive recreation uses specialized equipment and trained staff to serve people with disabilities.
Travel and tourism activities blend recreation with discovering new places and cultures. Popular options include cultural/heritage tourism, ecotourism, agritourism, wine tourism, culinary tourism, and more. Guided tours, themed trips, festivals and special events all help travelers engage with destinations. Experiential travel aimed at cultural immersion, adventure, and personalized enrichment is on the rise.
Lifelong learning programs on academic, vocational, or recreational topics are an important category. These range from lectures, seminars and workshops on history, science, art, finance, home improvement, and much more. Special interest clubs around hobbies like gardening, book groups, and chess provide regular chances to interact with like-minded peers while developing skills and knowledge.
Social recreation revolves around casual gatherings and structured events that bring communities together. municipal programming includes concerts, movies in the park, festivals, block parties, holiday celebrations, and entertainment series. Recreation facilities like community centers, senior centers, and clubs host dances, potlucks, game nights, craft fairs, dinner theaters, talent shows, and similar activities. Parks and recreation departments partner with public libraries, schools, businesses, civic organizations, and volunteers to provide inclusive social programming.
Technology has opened up new realms of digital recreation and social connection. Online gaming, media streaming, and interactive apps provide entertainment. Social media platforms enable networking around hobbies, advice-sharing, reconnecting with old friends, and exploring interests. Creative digital outlets like photo editing, blogging, video creation, and music mixing allow self-expression. Virtual and augmented reality expand interactive possibilities. Digital programming facilitates hybrid events, remote learning, and civic engagement.
A key consideration for recreation professionals is ensuring affordable access across the socioeconomic spectrum. Scholarships, discounted fees, joint-use agreements, outreach to underserved groups, multilingual communication, accessible design, loaner equipment, and inclusive policies help break down barriers. Building strong community partnerships and understanding diverse local needs are essential for successful public recreation. Adaptability and innovation will be ongoing necessities as recreation evolves with emerging technologies and societal changes.
Management And Park Maintenance
America’s National Park System
Managing America’s extensive National Park System requires a complex interplay of departments, professionals, policies, and partnerships. With over 400 park sites spanning 85 million acres, the system’s scale and diversity necessitates careful coordination. Furthermore, the National Park Service budget is approximately $4 billion and it employs a permanent staff base of 15,400 individuals. “For every $1 Congress invests in national parks, visitor spending returns over $10 to the U.S. economy” (NPS Office of Communications, 2023, para. 3).
At the helm of each park is a superintendent, who oversees all operations and staff. Superintendents must balance resource conservation, visitor access, facilities management, and partnerships. Critical duties include implementing park management plans, coordinating with other agencies, ensuring compliance with laws and regulations, managing budgets and personnel, and reporting to regional directors. Leadership, collaboration, science, and policy expertise are crucial superintendent qualifications.
Park rangers are the public face of the National Park Service (NPS), providing frontline visitor services and law enforcement (Fig. below). Interpretive rangers lead tours, give talks, provide information, and educate the public about park resources. Protection rangers enforce laws, conduct search and rescue operations, manage crowds and traffic, respond to emergencies, and ensure visitor safety. Other ranger specialties include wildlife management, resources management, firefighting, and administration. Seasonal rangers supplement the workforce during peak visitation.
Resource management and science staff assess environmental conditions, study flora and fauna, mitigate human impacts, and restore ecosystems. Experts include biologists, ecologists, botanists, hydrologists, wildlife biologists, natural resource specialists and geographic information systems analysts. They monitor air and water quality, assess endangered species, track invasive species, study diseases, and research climate change impacts (Fig below). This knowledge informs science-based decision making for sustainability.
Cultural resource professionals preserve archeological sites, historic structures, cultural landscapes, museum artifacts, and ethnographic resources. Archeologists, historians, curators, archivists and anthropologists identify, evaluate and nominate park resources for listing in the National Register of Historic Places. Ongoing research and documentation aids protection and interpretation.
Facility managers handle the NPS infrastructure portfolio including buildings, roads, trails, campgrounds, utilities, fleet vehicles and equipment. Planners forecast future facility needs and oversee construction projects. Facility operations specialists manage maintenance, housekeeping, property management, energy/water systems, groundskeeping, janitorial services and repairs. They ensure safe, code-compliant sites.
Administrators provide critical business operations support across human resources, budget/finance, contracting, information technology, and public affairs. They coordinate policies, procurement, records, agreements, public involvement, and government compliance. Centralized administrative programs enable efficient systemwide oversight.
Park education staff connect visitors to resources through talks, school programs, digital media, publications, visitor centers, and more. Curricula are designed to inspire lifelong learning and conservation action beyond park boundaries. Accessibility, inclusiveness, and contextualization ensure relevant, meaningful engagement with diverse audiences.
By working across disciplines, parks aim for integrated, holistic management. Interdepartmental collaboration and team building fosters systemwide thinking. Best practices and data are shared via online platforms and communities of practice. Advisory committees and partners provide outside expertise. Thanks to professionalism across all levels, parks can fulfill their inspiring yet enormously complex mission.
Looking forward, park managers will be challenged by rising visitation, climate impacts, expanding infrastructure demands, and constrained budgets. Maintaining relevance and building constituency support will be crucial. Continual workforce development and student pipelines can bring fresh perspectives. Leveraging technology for sustainability and access offers opportunities. Through coordinated effort that harnesses collective knowledge, our shared national park legacy can be safeguarded for generations to come.
State Park Systems in the USA
State park systems represent vital public green spaces and recreational resources across the United States. While narrower in scope than national parks, state park networks face similar management complexities stemming from ecological diversity, recreational demands, facilities upkeep, and lean budgets.
Most states have government agencies overseeing state park operations and planning. Agency duties include acquiring land, developing facilities, setting policies, managing capital projects and budgets, and promoting tourism. Oversight comes from commissioners, boards, or directors appointed by governors or legislatures. Supporting foundations often aid fundraising.
Park operations are led by managers or superintendents overseeing staff that provide law enforcement, maintenance, programs, visitor services, natural resource management, and administration. Larger parks may be divided into sectors with area supervisors. Managers have extensive duties running their park like a small city.
Visitor services/interpretation staff offer educational talks, tours, exhibits and junior ranger programs. They orient visitors to park resources and build appreciation. Law enforcement rangers handle public safety, emergencies, SAR, rules compliance, and managing crowds. Maintenance teams handle infrastructure upkeep and repairs. Natural resource specialists conduct resource management, monitoring and ecosystem restoration.
Behind the scenes, administrators oversee personnel, budgets, concessions, contracts, IT, public involvement, capital projects, and government liaison. They ensure operational efficiency, policy compliance, and fiscal responsibility. Centralized administration provides systemwide oversight and shared services.
Reaching beyond park boundaries, agency community partnership coordinators build relationships with schools, tourism promoters, Friends groups, recreation providers, land managers, municipalities and other stakeholders. Outreach, special events and volunteerism expand engagement.
Heavily utilized parks may have over 100 permanent staff, while remote parks function with just a manager and few rangers. Seasonal workers and embedded partners like universities boost capacity. Ongoing training and leadership development equip the workforce to grow professionally despite lean state budgets.
Looking ahead, state park systems face ecological threats, aging infrastructure, and shifting recreation patterns. Climate resilience, relevance to urban populations, equitable access, youth engagement, and public transit connections are rising priorities. Partnerships, philanthropy, fee-based revenue, grant funding, and interagency collaboration provide management support to keep these cherished places thriving.
With careful stewardship of human, financial, and natural resources, state park leaders can sustain these conserved public lands. Blending innovation with institutional knowledge will be key. By adapting creatively to emerging challenges, state park systems can continue providing cherished natural escapes that renew people’s spirits for generations to come.
Global influence of the U.S. National Park System
Some international conservation scholars and practitioners have criticized the U.S. national park system (Dowie, 2009). The parks have been called too protectionist, exclusionary, and old-fashioned in their approach Furthermore, some professionals in lesser developed countries have had difficulty emulating the U.S.’s park system network for various reasons, which has been frustrating and led some to refer to the NPS’s approach to park management as irrelevant to them. Finally, there are contentious claims in the history of NPS. First Nations rights people have begun using the term “Yellowstone model” in reference to the removal of people from a landscape for preservation purposes. Taking into account these problematic qualities, the global spread of the U.S. National Park system has had mixed impacts, particularly in recent decades.
Today, there are 6,500 national parks across nearly 100 countries; explore the Protected Planet site for parks and protected areas. These parks support wildlife conservation and ecotourism but many also have a tainted legacy of contributing to land violations and indigenous injustices. A good example of how a network of global national park systems are important on a worldwide scale could include tiger tourism and the parks set aside for their habitation.
Tiger Tourism in India
Tiger habitats span 10 countries across Asia – India, Nepal, Bhutan, Bangladesh, Myanmar, Thailand, Malaysia, Indonesia, China, and Russia. India is home to approximately 80% of the world’s wild tigers. It is also the primary destination for tiger tourism (Karanth et al., 2017).
By the late 1980s the tiger’s universal appeal was attracting numerous affluent and middle-class visitors to India’s tiger reserves. The framework for these reserves, which now number 53 spanning some 70,000 km² across the country, was established in 1973 under Project Tiger, an ambitious initiative administered by the Indian Government’s National Tiger Conservation Authority. Tiger reserves now receive >1 million visitors on an annual basis. For decades, tiger tourism provided considerable economic benefits to communities around the reserves, thereby boosting social support for tiger conservation (Karanth et al., 2017).
However, pressures and disturbances from tiger tourism escalated in ensuing decades. By 2012, tiger conservationists filed numerous court cases, seeking more regulation of visitors. The result was a series of legal battles with the tourism industry and reserve managers, ultimately concluding with temporary bans prohibiting entry by tourists to core areas of the reserves (Karanth & Karanth, 2012).
At present, high-end tiger tourism occupies less than 10% of the area spanning 70,000 km² in tiger reserves. Considering that all of India’s potential tiger habitats span 380,000 km², the presence of tiger tourism accounts for only 1-2% of the big cat’s entire country-wide habitat.
If managed correctly, tiger tourism can expand tiger habitats and augment their populations outside government-owned reserves. Some proponents of tiger tourism are pushing for wildlife tourism operators to gain access to privately owned land adjacent to the reserves. This could be done on long-term leases or by including farmers on those lands as shareholders. If successful, this expansion of habitat would allow more tourists to experience India’s nature while potentially building public support for and contributing to tiger conservation.
Further challenges facing National Parks
In many cases, national parks have taken the form of “islands” within human-dominated developed lands. As human societies further develop land around national parks, this isolation is projected to increase considerably. The wildlife populations within national parks do not recognize park or country borders so ecological wildlife corridors must be established and maintained to provide travel pathways on lands outside of parks. Many governments worldwide have already begun to address the issue of habitat fragmentation through the establishment of wildlife corridors. In south Texas, home to the country’s last remaining populations of ocelots (Leopardus pardalis), urban sprawl and development have taken their toll on the rare felids. As development fragments and degrades the animals’ habitats, ocelots are forced to cross busy roadways where they face serious dangers from passing vehicles.
Since 2005 conservationists have partnered with the Laguna Atascosa National Wildlife Refuge to construct a network of 14 road underpasses to facilitate safe crossings by ocelots and other animals. U.S. Fish and Wildlife Service zone biologist Mitch Sternberg hopes the underpasses will increase the ocelots’ chances of survival. As Sternberg stated, “Our mission here is wildlife sustainability. We want to maintain public wildlife recreation opportunities and maintain the integrity of the area for future generations of Americans” (as cited in Morse, 2022, para. 22).
2.4.7 Types Of Leisure Activities And Programs
According to John Neulinger, a German-American psychologist who studied the field of leisure studies, there are 3 main attributes of leisure activities (Neulinger, 1976):
- The experience is a state of mind;
- It must be entered voluntarily; and
- It must be intrinsically motivating of its own merit
In developed countries, leisure activities include literature, art and music.
In many low-income countries, where people commonly live according to day-to-day outlooks, leisure activities take an entirely different form. Indeed, many activities that are considered recreational in high-income countries are fundamental means of livelihood in low-income countries, e.g. fishing and construction of handicrafts.
In most communities the type of leisure activities are determined by variables such as age, gender, geography (e.g., rural vs. urban) and socioeconomic rank. In poor and rural communities there are usually no designated places for people to spend their leisure time, such as community centers and sports stadiums. Instead, people in these areas commonly gather in places of worship, neighborhood homes, and open spaces (Kaczynski & Henderson, 2017).
Participation in leisure activities has numerous benefits at both the individual and community-level. These benefits include:
- Health promotion and disease prevention – leisure activities are an enjoyable and effective way to enhance overall health and well-being; they can lower stress, improve fitness, and prevent the development of chronic diseases;
- Development of essential skills – physical and social skills can be developed through participation in leisure activities, especially at the community level;
- International peace and development – leisure activities can be considered a universal language and used as an efficient tool to promote peace, tolerance and mutual understanding of people across political boundaries, cultures, and religions (Iwasaki, 2007).
- Empowerment – leisure activities can empower people by positively influencing their self-confidence and self-esteem and sense of awareness (Green, 1998).
Attributions
- Figure 2.12: Glacier National Park by Dave Sizer is released under CC BY 2.0
- Figure 2.13: Yosemite by nestor ferraro is released under CC BY 2.0
- Figure 2.14: 20120106-OC-AMW-0635 by US Department of Agriculture in the Public Domain; Materials produced by federal agencies are in the public domain and may be reproduced without permission.
- Figure 2.15: City park in Poznan by Twisted Realm is released under CC BY 2.0
- Figure 2.16: Indonesia Rainforest in 2022 by Joe Figel, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 2.17: Ranger Sene inspects a backcountry permit by Jacob W. Frank/National Park Service in the Public Domain; Unless otherwise noted, all images and video posted here are in the public domain and may be used without permission or compensation.”
- Figure 2.18: Lynx Project Team by James Weliver/USFWS in the Public Domain; Materials produced by federal agencies are in the public domain and may be reproduced without permission.
- Figure 2.19: Map of Royal Belum National Park by Joe Figel, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 2.20: 300,000 views!! Thank You, Friends! by Koshy Koshy is released under CC BY 2.0
- Figure 2.21: Ocelot Sign in the Refuge by Erin is released under CC BY-NC-ND 2.0
- Figure 2.22: Walking by PAM Phạm is released under CC BY-NC 2.0
Please look for related terms in the Glossary.
travel within one's own country or nation, as opposed to international travel to foreign countries.
the cultural, political, and intellectual movement that critiques and examines the legacy of colonialism, imperialism, and hegemony, emphasizing decolonization, cultural diversity, and social justice.
parks, gardens, and natural areas within cities and urban environments, providing residents and visitors with opportunities for recreation, relaxation, and connection with nature.
shared plots of land cultivated by local residents for growing fruits, vegetables, flowers, and herbs, promoting community engagement, food security, and sustainability.
adventurous and high-risk recreational activities that involve physical challenges, adrenaline rushes, and daring feats, such as skydiving, bungee jumping, rock climbing, and whitewater rafting.
a social and political movement advocating for the protection, conservation, and sustainable management of natural resources, ecosystems, and the environment, as well as addressing environmental issues such as pollution, climate change, and biodiversity loss.
the scientific study of aging and the processes, experiences, and issues related to older adults, including health, well-being, social integration, and quality of life.
an interdisciplinary field of academic inquiry that examines the experiences, behaviors, identities, and social contexts of young people, addressing issues such as education, employment, leisure, and transition to adulthood.
Tourism activities and experiences centered around agricultural operations, farms, or rural areas. Agritourism offers visitors opportunities to engage in farm-related activities, learn about agriculture, and experience rural lifestyles.
a form of tourism that focuses on visiting wineries, vineyards, and wine-producing regions to learn about winemaking, tasting wines, and experiencing local cuisine and culture.
traveling to destinations or regions specifically to explore and experience the local food, cuisine, gastronomy, and culinary traditions.
the customer-facing roles and activities provided by tourism professionals and staff to assist visitors with information, assistance, and support during their travels.
Flora refers to the plant species found in a particular region or ecosystem, while fauna refers to the animal species.
scientists who study plants, including their classification, structure, physiology, ecology, and distribution.
scientists who study the distribution, movement, and quality of water on Earth, including surface water, groundwater, and the hydrological cycle.
professionals with expertise in managing and conserving natural resources, including land, water, minerals, forests, and wildlife.
scientists who study the behavior, ecology, population dynamics, and conservation of wild animal species and their habitats.
computer-based tools and technologies used to capture, analyze, and visualize spatial data and geographic information for mapping, modeling, and decision-making purposes.
objects, specimens, or items of cultural, historical, or scientific significance preserved and displayed in museums for educational, research, and public enjoyment purposes.
cultural materials, artifacts, traditions, and knowledge associated with specific ethnic groups, cultures, or societies.
scholars who study and interpret past events, developments, and narratives based on written records, documents, archives, and oral histories.
museum professionals responsible for the care, preservation, and interpretation of collections, artifacts, and exhibits, as well as developing exhibitions and educational programs.
professionals who collect, preserve, organize, and provide access to historical documents, records, manuscripts, and archives for research, reference, and cultural heritage purposes.
social scientists who study human societies, cultures, behaviors, and beliefs across time and space, employing methods such as ethnography, archaeology, and comparative analysis.


14 Fluid Mechanics
14.3 Pascal’s Principle and Hydraulics
Learning Objectives
By the end of this section, you will be able to:
- State Pascal’s principle
- Describe applications of Pascal’s principle
- Derive relationships between forces in a hydraulic system
In 1653, the French philosopher and scientist Blaise Pascal published his Treatise on the Equilibrium of Liquids, in which he discussed principles of static fluids. A static fluid is a fluid that is not in motion. When a fluid is not flowing, we say that the fluid is in static equilibrium. If the fluid is water, we say it is in hydrostatic equilibrium. For a fluid in static equilibrium, the net force on any part of the fluid must be zero; otherwise the fluid will start to flow.
Pascal’s observations—since proven experimentally—provide the foundation for hydraulics, one of the most important developments in modern mechanical technology. Pascal observed that a change in pressure applied to an enclosed fluid is transmitted undiminished throughout the fluid and to the walls of its container. Because of this, we often know more about pressure than other physical quantities in fluids. Moreover, Pascal’s principle implies that the total pressure in a fluid is the sum of the pressures from different sources. A good example is the fluid at a depth depends on the depth of the fluid and the pressure of the atmosphere.
Pascal’s Principle
Pascal’s principle (also known as Pascal’s law) states that when a change in pressure is applied to an enclosed fluid, it is transmitted undiminished to all portions of the fluid and to the walls of its container. In an enclosed fluid, since atoms of the fluid are free to move about, they transmit pressure to all parts of the fluid and to the walls of the container. Any change in pressure is transmitted undiminished.
Note that this principle does not say that the pressure is the same at all points of a fluid—which is not true, since the pressure in a fluid near Earth varies with height. Rather, this principle applies to the change in pressure. Suppose you place some water in a cylindrical container of height H and cross-sectional area A that has a movable piston of mass m (Figure). Adding weight Mg at the top of the piston increases the pressure at the top by Mg/A, since the additional weight also acts over area A of the lid:
According to Pascal’s principle, the pressure at all points in the water changes by the same amount, Mg/A. Thus, the pressure at the bottom also increases by Mg/A. The pressure at the bottom of the container is equal to the sum of the atmospheric pressure, the pressure due the fluid, and the pressure supplied by the mass. The change in pressure at the bottom of the container due to the mass is
Since the pressure changes are the same everywhere in the fluid, we no longer need subscripts to designate the pressure change for top or bottom:
Pascal’s Barrel is a great demonstration of Pascal’s principle. Watch a simulation of Pascal’s 1646 experiment, in which he demonstrated the effects of changing pressure in a fluid.
Applications of Pascal’s Principle and Hydraulic Systems
Hydraulic systems are used to operate automotive brakes, hydraulic jacks, and numerous other mechanical systems (Figure).
We can derive a relationship between the forces in this simple hydraulic system by applying Pascal’s principle. Note first that the two pistons in the system are at the same height, so there is no difference in pressure due to a difference in depth. The pressure due to [latex]{F}_{1}[/latex] acting on area [latex]{A}_{1}[/latex] is simply
According to Pascal’s principle, this pressure is transmitted undiminished throughout the fluid and to all walls of the container. Thus, a pressure [latex]{p}_{2}[/latex] is felt at the other piston that is equal to [latex]{p}_{1}[/latex]. That is, [latex]{p}_{1}={p}_{2}.[/latex] However, since[latex]{p}_{2}={F}_{2}\text{/}{A}_{2},[/latex] we see that
This equation relates the ratios of force to area in any hydraulic system, provided that the pistons are at the same vertical height and that friction in the system is negligible.
Hydraulic systems can increase or decrease the force applied to them. To make the force larger, the pressure is applied to a larger area. For example, if a 100-N force is applied to the left cylinder in Figure and the right cylinder has an area five times greater, then the output force is 500 N. Hydraulic systems are analogous to simple levers, but they have the advantage that pressure can be sent through tortuously curved lines to several places at once.
The hydraulic jack is such a hydraulic system. A hydraulic jack is used to lift heavy loads, such as the ones used by auto mechanics to raise an automobile. It consists of an incompressible fluid in a U-tube fitted with a movable piston on each side. One side of the U-tube is narrower than the other. A small force applied over a small area can balance a much larger force on the other side over a larger area (Figure).
From Pascal’s principle, it can be shown that the force needed to lift the car is less than the weight of the car:
where [latex]{F}_{1}[/latex] is the force applied to lift the car, [latex]{A}_{1}[/latex] is the cross-sectional area of the smaller piston, [latex]{A}_{2}[/latex] is the cross sectional area of the larger piston, and [latex]{F}_{2}[/latex] is the weight of the car.
Example
Calculating Force on Wheel Cylinders: Pascal Puts on the Brakes
Consider the automobile hydraulic system shown in Figure. Suppose a force of 100 N is applied to the brake pedal, which acts on the pedal cylinder (acting as a “master” cylinder) through a lever. A force of 500 N is exerted on the pedal cylinder. Pressure created in the pedal cylinder is transmitted to the four wheel cylinders. The pedal cylinder has a diameter of 0.500 cm and each wheel cylinder has a diameter of 2.50 cm. Calculate the magnitude of the force [latex]{F}_{2}[/latex] created at each of the wheel cylinders.
Strategy
We are given the force [latex]{F}_{1}[/latex] applied to the pedal cylinder. The cross-sectional areas [latex]{A}_{1}[/latex] and [latex]{A}_{2}[/latex] can be calculated from their given diameters. Then we can use the following relationship to find the force [latex]{F}_{2}[/latex]:
Manipulate this algebraically to get [latex]{F}_{2}[/latex] on one side and substitute known values.
Solution
Pascal’s principle applied to hydraulic systems is given by [latex]\frac{{F}_{1}}{{A}_{1}}=\frac{{F}_{2}}{{A}_{2}}:[/latex]
Significance
This value is the force exerted by each of the four wheel cylinders. Note that we can add as many wheel cylinders as we wish. If each has a 2.50-cm diameter, each will exert [latex]1.25\times {10}^{4}\,\text{N}\text{.}[/latex] A simple hydraulic system, as an example of a simple machine, can increase force but cannot do more work than is done on it. Work is force times distance moved, and the wheel cylinder moves through a smaller distance than the pedal cylinder. Furthermore, the more wheels added, the smaller the distance each one moves. Many hydraulic systems—such as power brakes and those in bulldozers—have a motorized pump that actually does most of the work in the system.
Check Your Understanding
Would a hydraulic press still operate properly if a gas is used instead of a liquid?
Show Solution
Yes, it would still work, but since a gas is compressible, it would not operate as efficiently. When the force is applied, the gas would first compress and warm. Hence, the air in the brake lines must be bled out in order for the brakes to work properly.
Summary
- Pressure is force per unit area.
- A change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of its container.
- A hydraulic system is an enclosed fluid system used to exert forces.
Conceptual Questions
Suppose the master cylinder in a hydraulic system is at a greater height than the cylinder it is controlling. Explain how this will affect the force produced at the cylinder that is being controlled.
Problems
How much pressure is transmitted in the hydraulic system considered in Figure? Express your answer in atmospheres.
Show Solution
251 atm
What force must be exerted on the master cylinder of a hydraulic lift to support the weight of a 2000-kg car (a large car) resting on a second cylinder? The master cylinder has a 2.00-cm diameter and the second cylinder has a 24.0-cm diameter.
A host pours the remnants of several bottles of wine into a jug after a party. The host then inserts a cork with a 2.00-cm diameter into the bottle, placing it in direct contact with the wine. The host is amazed when the host pounds the cork into place and the bottom of the jug (with a 14.0-cm diameter) breaks away. Calculate the extra force exerted against the bottom if he pounded the cork with a 120-N force.
Show Solution
[latex]5.76\times {10}^{3}\,\text{N}\,\text{extra force}[/latex]
A certain hydraulic system is designed to exert a force 100 times as large as the one put into it. (a) What must be the ratio of the area of the cylinder that is being controlled to the area of the master cylinder? (b) What must be the ratio of their diameters? (c) By what factor is the distance through which the output force moves reduced relative to the distance through which the input force moves? Assume no losses due to friction.
Verify that work input equals work output for a hydraulic system assuming no losses due to friction. Do this by showing that the distance the output force moves is reduced by the same factor that the output force is increased. Assume the volume of the fluid is constant. What effect would friction within the fluid and between components in the system have on the output force? How would this depend on whether or not the fluid is moving?
Show Solution
If the system is not moving, the friction would not play a role. With friction, we know there are losses, so that [latex]{W}_{\text{o}}={W}_{\text{i}}-{W}_{\text{f}};[/latex] therefore, the work output is less than the work input. In other words, to account for friction, you would need to push harder on the input piston than was calculated.
Glossary
- hydraulic jack
- simple machine that uses cylinders of different diameters to distribute force
- hydrostatic equilibrium
- state at which water is not flowing, or is static
- Pascal’s principle
- change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of its container


Chapter 20 Between the Stars: Gas and Dust in Space
20.3 Cosmic Dust
Learning Objectives
By the end of this section, you will be able to:
- Describe how we can detect interstellar dust
- Understand the role and importance of infrared observations in studying dust
- Explain the terms extinction and interstellar reddening
[link] shows a striking example of what is actually a common sight through large telescopes: a dark region on the sky that appears to be nearly empty of stars. For a long time, astronomers debated whether these dark regions were empty “tunnels” through which we looked beyond the stars of the Milky Way Galaxy into intergalactic space, or clouds of some dark material that blocked the light of the stars beyond. The astronomer William Herschel (discoverer of the planet Uranus) thought it was the former, once remarking after seeing one, “Here truly is a hole in heaven!” However, American astronomer E. E. Barnard is generally credited with showing from his extensive series of nebula photographs that the latter interpretation is the correct one (see the feature box on [link]).
Dusty clouds in space betray their presence in several ways: by blocking the light from distant stars, by emitting energy in the infrared part of the spectrum, by reflecting the light from nearby stars, and by making distant stars look redder than they really are.
Born in 1857 in Nashville, Tennessee, two months after his father died, Edward Barnard ([link]) grew up in such poor circumstances that he had to drop out of school at age nine to help support his ailing mother. He soon became an assistant to a local photographer, where he learned to love both photography and astronomy, destined to become the dual passions of his life. He worked as a photographer’s aide for 17 years, studying astronomy on his own. In 1883, he obtained a job as an assistant at the Vanderbilt University Observatory, which enabled him at last to take some astronomy courses.
Married in 1881, Barnard built a house for his family that he could ill afford. But as it happened, a patent medicine manufacturer offered a ?200 prize (a lot of money in those days) for the discovery of any new comet. With the determination that became characteristic of him, Barnard spent every clear night searching for comets. He discovered seven of them between 1881 and 1887, earning enough money to make the payments on his home; this “Comet House” later became a local attraction. (By the end of his life, Barnard had found 17 comets through diligent observation.)
In 1887, Barnard got a position at the newly founded Lick Observatory, where he soon locked horns with the director, Edward Holden, a blustering administrator who made Barnard’s life miserable. (To be fair, Barnard soon tried to do the same for him.) Despite being denied the telescope time that he needed for his photographic work, in 1892, Barnard managed to discover the first new moon found around Jupiter since Galileo’s day, a stunning observational feat that earned him world renown. Now in a position to demand more telescope time, he perfected his photographic techniques and soon began to publish the best images of the Milky Way taken up to that time. It was during the course of this work that he began to examine the dark regions among the crowded star lanes of the Galaxy and to realize that they must be vast clouds of obscuring material (rather than “holes” in the distribution of stars).
Astronomer-historian Donald Osterbrock has called Barnard an “observaholic:” his daily mood seemed to depend entirely on how clear the sky promised to be for his night of observing. He was a driven, neurotic man, concerned about his lack of formal training, fearful of being scorned, and afraid that he might somehow slip back into the poverty of his younger days. He had difficulty taking vacations and lived for his work: only serious illness could deter him from making astronomical observations.
In 1895, Barnard, having had enough of the political battles at Lick, accepted a job at the Yerkes Observatory near Chicago, where he remained until his death in 1923. He continued his photographic work, publishing compilations of his images that became classic photographic atlases, and investigating the varieties of nebulae revealed in his photographs. He also made measurements of the sizes and features of planets, participated in observations of solar eclipses, and carefully cataloged dark nebulae (see [link]). In 1916, he discovered the star with the largest proper motion, the second-closest star system to our own (see Analyzing Starlight). It is now called Barnard’s Star in his honor.
Detecting Dust
The dark cloud seen in [link] blocks the light of the many stars that lie behind it; note how the regions in other parts of the photograph are crowded with stars. Barnard 68 is an example of a relatively dense cloud or dark nebula containing tiny, solid dust grains. Such opaque clouds are conspicuous on any photograph of the Milky Way, the galaxy in which the Sun is located (see the figures in The Milky Way Galaxy). The “dark rift,” which runs lengthwise down a long part of the Milky Way in our sky and appears to split it in two, is produced by a collection of such obscuring clouds.
While dust clouds are too cold to radiate a measurable amount of energy in the visible part of the spectrum, they glow brightly in the infrared ([link]). The reason is that small dust grains absorb visible light and ultraviolet radiation very efficiently. The grains are heated by the absorbed radiation, typically to temperatures from 10 to about 500 K, and re-radiate this heat at infrared wavelengths.
Thanks to their small sizes and low temperatures, interstellar grains radiate most of their energy at infrared to microwave frequencies, with wavelengths of tens to hundreds of microns. Earth’s atmosphere is opaque to radiation at these wavelengths, so emission by interstellar dust is best measured from space. Observations from above Earth’s atmosphere show that dust clouds are present throughout the plane of the Milky Way ([link]).
Some dense clouds of dust are close to luminous stars and scatter enough starlight to become visible. Such a cloud of dust, illuminated by starlight, is called a reflection nebula, since the light we see is starlight reflected off the grains of dust. One of the best-known examples is the nebulosity around each of the brightest stars in the Pleiades cluster (see [link]). The dust grains are small, and such small particles turn out to scatter light with blue wavelengths more efficiently than light at red wavelengths. A reflection nebula, therefore, usually appears bluer than its illuminating star ([link]).
Gas and dust are generally intermixed in space, although the proportions are not exactly the same everywhere. The presence of dust is apparent in many photographs of emission nebulae in the constellation of Sagittarius, where we see an H II region surrounded by a blue reflection nebula. Which type of nebula appears brighter depends on the kinds of stars that cause the gas and dust to glow. Stars cooler than about 25,000 K have so little ultraviolet radiation of wavelengths shorter than 91.2 nanometers—which is the wavelength required to ionize hydrogen—that the reflection nebulae around such stars outshine the emission nebulae. Stars hotter than 25,000 K emit enough ultraviolet energy that the emission nebulae produced around them generally outshine the reflection nebulae.
Interstellar Reddening
The tiny interstellar dust grains absorb some of the starlight they intercept. But at least half of the starlight that interacts with a grain is merely scattered, that is, it is redirected rather than absorbed. Since neither the absorbed nor the scattered starlight reaches us directly, both absorption and scattering make stars look dimmer. The effects of both processes are called interstellar extinction ([link]).
Astronomers first came to understand interstellar extinction around the early 1930s, as the explanation of a puzzling observation. In the early part of the twentieth century, astronomers discovered that some stars look red even though their spectral lines indicate that they must be extremely hot (and thus should look blue). The solution to this seeming contradiction turned out to be that the light from these hot stars is not only dimmed but also reddened by interstellar dust, a phenomenon known as interstellar reddening.
Dust does not interact with all the colors of light the same way. Much of the violet, blue, and green light from these stars has been scattered or absorbed by dust, so it does not reach Earth. Some of their orange and red light, with longer wavelengths, on the other hand, more easily penetrates the intervening dust and completes its long journey through space to enter Earth-based telescopes ([link]). Thus, the star looks redder from Earth than it would if you could see it from nearby. (Strictly speaking, reddening is not the most accurate term for this process, since no red color is added; instead, blues and related colors are subtracted, so it should more properly be called “deblueing.”) In the most extreme cases, stars can be so reddened that they are entirely undetectable at visible wavelengths and can be seen only at infrared or longer wavelengths ([link]).
We have all seen an example of reddening on Earth. The Sun appears much redder at sunset than it does at noon. The lower the Sun is in the sky, the longer the path its light must travel through the atmosphere. Over this greater distance, there is a greater chance that sunlight will be scattered. Since red light is less likely to be scattered than blue light, the Sun appears more and more red as it approaches the horizon.
By the way, scattering of sunlight is also what causes our sky to look blue, even though the gases that make up Earth’s atmosphere are transparent. As sunlight comes in, it scatters from the molecules of air. The small size of the molecules means that the blue colors scatter much more efficiently than the greens, yellows, and reds. Thus, the blue in sunlight is scattered out of the beam and all over the sky. The light from the Sun that comes to your eye, on the other hand, is missing some of its blue, so the Sun looks a bit yellower, even when it is high in the sky, than it would from space.
The fact that starlight is reddened by interstellar dust means that long-wavelength radiation is transmitted through the Galaxy more efficiently than short-wavelength radiation. Consequently, if we wish to see farther in a direction with considerable interstellar material, we should look at long wavelengths. This simple fact provides one of the motivations for the development of infrared astronomy. In the infrared region at 2 microns (2000 nanometers), for example, the obscuration is only one-sixth as great as in the visible region (500 nanometers), and we can therefore study stars that are more than twice as distant before their light is blocked by interstellar dust. This ability to see farther by observing in the infrared portion of the spectrum represents a major gain for astronomers trying to understand the structure of our Galaxy or probing its puzzling, but distant, center (see The Milky Way Galaxy).
Interstellar Grains
Before we get to the details about interstellar dust, we should perhaps get one concern out of the way. Why couldn’t it be the interstellar gas that reddens distant stars and not the dust? We already know from everyday experience that atomic or molecular gas is almost transparent. Consider Earth’s atmosphere. Despite its very high density compared with that of interstellar gas, it is so transparent as to be practically invisible. (Gas does have a few specific spectral lines, but they absorb only a tiny fraction of the light as it passes through.)The quantity of gas required to produce the observed absorption of light in interstellar space would have to be enormous. The gravitational attraction of so great a mass of gas would affect the motions of stars in ways that could easily be detected. Such motions are not observed, and thus, the interstellar absorption cannot be the result of gases.
Although gas does not absorb much light, we know from everyday experience that tiny solid or liquid particles can be very efficient absorbers. Water vapor in the air is quite invisible. When some of that vapor condenses into tiny water droplets, however, the resulting cloud is opaque. Dust storms, smoke, and smog offer familiar examples of the efficiency with which solid particles absorb light. On the basis of arguments like these, astronomers have concluded that widely scattered solid particles in interstellar space must be responsible for the observed dimming of starlight. What are these particles made of? And how did they form?
Observations like the pictures in this chapter show that a great deal of this dust exists; hence, it must be primarily composed of elements that are abundant in the universe (and in interstellar matter). After hydrogen and helium, the most abundant elements are oxygen, carbon, and nitrogen. These three elements, along with magnesium, silicon, iron—and perhaps hydrogen itself—turn out to be the most important components of interstellar dust.
Many of the dust particles can be characterized as sootlike (rich in carbon) or sandlike (containing silicon and oxygen). Grains of interstellar dust are found in meteorites and can be identified because the abundances of certain isotopes are different from what we see in other solar system material. Several different interstellar dust substances have been identified in this way in the laboratory, including graphite and diamonds. (Don’t get excited; these diamonds are only a billionth of a meter in size and would hardly make an impressive engagement ring!)
The most widely accepted model pictures the grains with rocky cores that are either like soot (rich in carbon) or like sand (rich in silicates). In the dark clouds where molecules can form, these cores are covered by icy mantles ([link]). The most common ices in the grains are water (H2O), methane (CH4), and ammonia (NH3)—all built out of atoms that are especially abundant in the realm of the stars. The ice mantles, in turn, are sites for some of the chemical reactions that produce complex organic molecules.
Typical individual grains must be just slightly smaller than the wavelength of visible light. If the grains were a lot smaller, they would not block the light efficiently, as [link] and other images in this chapter show that it does.
On the other hand, if the dust grains were much larger than the wavelength of light, then starlight would not be reddened. Things that are much larger than the wavelength of light would block both blue and red light with equal efficiency. In this way we can deduce that a characteristic interstellar dust grain contains 106 to 109 atoms and has a diameter of 10–8 to 10–7 meters (10 to 100 nanometers). This is actually more like the specks of solid matter in cigarette smoke than the larger grains of dust you might find under your desk when you are too busy studying astronomy to clean properly.
Key Concepts and Summary
Interstellar dust can be detected: (1) when it blocks the light of stars behind it, (2) when it scatters the light from nearby stars, and (3) because it makes distant stars look both redder and fainter. These effects are called reddening and interstellar extinction, respectively. Dust can also be detected in the infrared because it emits heat radiation. Dust is found throughout the plane of the Milky Way. The dust particles are about the same size as the wavelength of light and consist of rocky cores that are either sootlike (carbon-rich) or sandlike (silicates) with mantles made of ices such as water, ammonia, and methane.
Glossary
- interstellar extinction
- the attenuation or absorption of light by dust in the interstellar medium
- reddening (interstellar)
- the reddening of starlight passing through interstellar dust because dust scatters blue light more effectively than red


19 Victims of Human Trafficking
Human trafficking victims can be of any age, race, ethnicity, sex, gender identity, sexual orientation, nationality, immigration status, cultural background, religion, socio-economic class, and education attainment level. In the United States, individuals vulnerable to human trafficking include children in the child welfare and juvenile justice systems, including foster care; runaway and homeless youth; unaccompanied foreign national children without lawful immigration status; individuals seeking asylum; American Indians and Alaska Natives, particularly women and girls; individuals with substance use issues; racial or ethnic minorities; migrant laborers, including undocumented workers and participants in visa programs for temporary workers; foreign national domestic workers in diplomatic households; persons with limited English proficiency; persons with disabilities; LGBTQI+ individuals; and victims of intimate partner violence or other forms of domestic violence.
There is no single profile of a trafficking victim.
Vulnerabilities
Although there is no defining characteristic that all human trafficking victims share, traffickers around the world frequently prey on individuals whose vulnerabilities, including poverty, limited English proficiency, or lack of lawful immigration status, are exacerbated by lack of stable, safe housing, and limited economic and educational opportunities. Trafficking victims are deceived by false promises of love, a good job, or a stable life and are lured or forced into situations where they are made to work under deplorable conditions with little or no pay. In the United States, trafficking victims can be American or foreign citizens.
Locations
Victims can be found in legal and illegal labor industries, including child care, elder care, the drug trade, massage parlors, nail and hair salons, restaurants, hotels, factories, and farms. In some cases, victims are hidden behind doors in domestic servitude in a home. Others are in plain view, interact with people on a daily basis, and are forced to work under extreme circumstances in exotic dance clubs, factories, or restaurants. Victims can be exploited for commercial sex in numerous contexts, including on the street, in illicit massage parlors, cantinas, brothels, or through escort services and online advertising. Trafficking situations can be found across the United States.
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