Functions and Variables in Physical Science Experiments
Almost all true science experiments involve designing a series of trials where one variable is manipulated and another variable changes as a result of this manipulation. All other variables are held constant. A variable is said to be a function of another variable if, for various values of x, it is possible to establish corresponding values of y, i.e. y = 6x.
In todayıs lab you will be working with various weights that can be hung on a spring. Work in pairs to determine any connections between the variables that you choose to investigate. Any spring will deform if you put a large amount of weight on it. The purpose of this lab is NOT to see how much weight a spring will take before it breaks or deforms. Deforming a spring by using an excess of weight, will ruin your experiment and it will force us to buy new springs. You can keep the lab fees from increasing if you use a reasonable amount of weight on the springs. Be nice to your springs.
When you have written a question and identified the variables you want to investigate, conduct an experiment to see what effect changing one variable has on another variable. Prior to beginning your experiment, you need to check your question and your procedure with your instructor. Please be sure to describe what experiment you are conducting and what materials you are using (the procedure) in your lab notebook (or if this is the first lab, use this sheet of paper). The level of detail you include in your procedure should allow someone to repeat your experiment just by reading your procedure. All data, observations, calculations, graphs, diagrams, etc. should be recorded in your lab notebook as well. Be sure to include appropriate units with all measurements and results of calculations. You will need to follow the rules for working with significant figures.
The expectations for this lab experiments are: a) you need to run a minimum of two different experiments, b) you need to collect a minimum of five data points for each experiment, c) you need to run each experiment twice and average your data, d) record your data for each experiment in a data table, e) there are at least two different types of springs, use them, describe them, make a comparison, f) for each experiment you do, plot a graph using the average values of your variables (when appropriate), g) identify at least two resulting relationships, h) include an algebraic expression (a mathematical equation and a written statement) describing the correlation between your variables, i) show how your data fits the equation.
Beginning Questions: In this lab you are faced with determining relationships between multiple variables. What are two initial questions that can be answered by doing this lab activity?
Procedure. Identify your dependent variable and your independent variable. What variables are kept constant?
Data/ Observations: (attach a separate piece of paper) Record all data and observations. Include appropriate units.
Graphs (attach graph paper). The dependent variable is plotted on the _____ axis and the independent variable is plotted on the _____ axis. Be sure to calculate the slope of each graph.
Claims: Based on the data collected, the graphs, etc. what claims can be made?
Evidence: Support your claims with appropriate evidence.
Reading/ Reflection: What are some of the principles that you have learned or applied in this lab? How does this compare to other groups? How does this compare to information found in a physics textbook? Compare graphs when using the thick wire/heavy spring vs. the thin wire/light spring, what physical variable does the slope of these graphs represent?
Please show how you arrived at your answers to each of the following questions using a) your algebraic expression, b) your graph. How does your equation or graph tell the difference between the two springs?
If a 63 gram weight is hung on the longer spring, what would be the amount of stretching? What would be the length of the spring? Does it make a difference if you investigate the length of the spring or the amount of stretching of the spring?
If a 63 gram weight is hung on the shorter spring, what would be the amount of stretching? What would be the length of the spring?