Okay, so I am an orthopedic surgeon and orthopedic sports medicine is my subspecialty. So I take care of a wide range of patients, but younger patients with hip pain is one thing that I take care of a lot of patients for. And so that's sort of the theme for this talk is young and middle-aged patients with hip pain and femoroastabular impingement or FAI is probably the most common cause of hip pain in patients, in younger hip patients, patients who do not have hip arthritis. Certainly hip arthritis when we get older is more common, but in younger patients, FAI and labral tears are the most common thing. So that's sort of why I have a centered topic. I have no disclosures relevant. And I'll start with a case to sort of display a typical scenario that I see a lot and isn't very common. So a younger patient, a 26-year-old female with hip pain for years, no specific injury, gradual onset, the pain is anterior toward the groin, which is very common location for true hip pain from pain from intraarticular in the hip joint itself. And she has some clicking and her pain is worse with sitting, pivoting and impact exercise. And so that's a problem for her because she can't do her normal exercise. Her physical exam shows good flexion of the hip. She has limited internal rotation, only 10 degrees compared to 20 degrees in her other hip, but she has good strength. The fader test is adduction internal rotation test, which is a test that we commonly use to test for pain in the hip joint. And so she's positive there and many of the other tests are negative. We don't have to go into those right now. So there's three standard x-rays that I get for a patient with hip pain, the first of which is a AP pelvis. And so I have them do this standing, but this shows us both hips so we can compare. And in her, we see that she has, does my pointer show up? Yes. Okay, great. So it shows that there's good space in the joint, meaning she does not have arthritis and she's young anyways. But there's good space in both of her hips. Her right hip is the one that bothers her. A done 45 is rotating the hips slightly. And so this view is good for young people because this brings out what we call the CAM lesion, C-A-M, the CAM lesion. And so what that means is instead of the ball being rounded, like on the under surface, you see how it's rounded and it curves in. On the top, it just goes straight down. So this is abnormal bone. This is extra bone on the femur side. And this I'll explain more as we go, but this leads to impingement. And so this 45 done view is a good x-ray to get to look for this CAM lesion. And I get this in everyone. This is how you measure how much extra bone there is. It's something called the alpha angle. But the ball's supposed to be perfectly round. Bone that's sticking out outside the round ball, that's the abnormal bone. And then the false profile is the third view. So the three views are AP pelvis, a done 45, and a false profile. And this is rotating the pelvis. So this gives us a side view of the pelvis. So those are the three x-rays that are the best to get for younger people with hip pain. And this shows us the front of the socket. This is the front edge of the socket here. And this shows that she has normal anatomy of her hip socket. So from this, my diagnosis is femurous tabular impingement syndrome, which I'll break down further as we go into this. But this would be a common scenario. Someone young with some hip pain for a few years hasn't really had any treatment. And so we generally treat this conservatively first. So FAI and many things that get young people pain in the hip respond to physical therapy in general. And so we start treating this with physical therapy. Whether we need an MRI is up for debate. And we can talk about that as we go further. But in general, most young people that are having pain in the hip can be treated starting with physical therapy. They don't have to have an MRI. I would say, I'll say now and I'll say it again, one of the reasons to get an MRI in a young person is if you're worried about a stress fracture. And a stress fracture, a common scenario that you might see is someone that has recently picked up running or recently increased the amount that they run. And now they're getting pain that's associated with either the running or bearing weight. And those patients, you should get an MRI right away on. And the insurance company will authorize that always if you're ruling out a stress fracture. So that's a good reason to get an MRI. Otherwise, most things can wait on getting the MRI. So she had an MRI. And what it shows, this is the side view. This is the labrum, the black right here. This is a tear in the labrum. And this is a cyst in the bone. And this is caused by the impingement that we'll talk about more. Here's another view.  The labrum is this triangle. And it's supposed to be all black. Here's it from the side views, or sorry, from the straight odd views. This is coronal. So here's the socket. Here's the femoral head. The labrum is black, but it's supposed to be a perfect black triangle. This gray that comes through here is the tear. And the only other thing the MRI shows you is a little cyst in the bone here on the ball side. And that's caused by the impingement as well. So she didn't get better with physical therapy. She wanted to avoid surgery. So she tried an injection as well. And that helped, but wore off in two to three weeks. And she kept doing therapy. And eventually, she couldn't get to the point where she wanted, so she chose to have surgery. And this is what hip surgery looks like arthroscopically. So this is putting the camera inside the hip. So this is the ball, femoral head on this side. The socket's on this side. This is the labrum. And this is abnormal because you're supposed to be able to see inside between the ball and socket here. This is, we pull traction on the leg to make space between the femoral head and the acetabulum here. And so you're supposed to see the space. This labrum is torn, it is falling down off the labrum and is in between. And so that tells us that this whole labrum is unstable. So this is what it looks like when you repair the labrum. So if you compare this top left picture to the bottom middle picture, this is what it's supposed to look like. This is after I repaired it. The labrum is supposed to be right on the edge of the socket. And so you can see how dramatically it was all separated and off the bone. And so I've repaired back to the bone there. There's another view of it. And then this is when we let go of the leg so we're not pulling traction anymore. And so the ball goes right back into the socket and the labrum forms a nice seal. And then the other thing we do is I talked about this extra bump of bone. That's the cam lesion. We remove this bone. And so this is what it looks like. The top row is the arthroscopic pictures. And then at the same time, we do fluoroscopy to get X-ray views. And that's what it looks like before. And this is what it looks like after you remove that extra bump of bone so that the ball is round. So it looks like it curves in on the top just like it does on the bottom. And this is all the abnormal bone that we remove with the burr to make it smooth down and so that it's round so it doesn't impact. And then this is just closing the ligaments to get into the hip. You have to cut through the ligaments to get in and stitch the ligaments back up together on the way out. And that's what it looks like after. See, you can compare her hip that we've now fixed to her up is not stigmatic, but she has the same cam lesion bone. But this is what it's supposed to look like, yeah. And so in general, these people are on touches for two weeks or three months. They start running and at six months they get back to playing sports. So the surgery is some recovery, but it is minimally invasive and arthroscopic. So it's not very painful surgery, but it does take time to fully recover to go back to playing sports and being a young active person. So here's the objective for today would be to recognize the sources of pre-arthritic hip pain. So hip pain in younger patients that don't have arthritis yet, which imaging to get, I've gone through the x-rays and we'll cover more. But those x-ray views that we wanna get in young patients, labral tears are very common. We're gonna talk more about that, but there are, it's caused by something and there's multiple things that can cause it. So you wanna know why the person has a labral tear. And then we're gonna talk mostly about femurous to have an impingement syndrome or FAI. So in general, when a young patient comes in with hip pain, this is sort of how I do my difference. So when I sort of do it based on the location of pain because location of pain in the hip is pretty good at pointing you to what the problem is. So I divide it into groin or pain in the front of the hip, on the side of the hip or in the back. And so groin or anterior pain is the most common thing. So I'll say that FAI is the most common and labral tears. Now, of course, hip flexor strenghens are common in resolve with time. Snapping hip is when the hip flexor is snapping over the hip. Displasia, so hip dysplasia, which we know about when babies have a dysplasia. But as people get older, not everyone's dysplasia were picked up when we were kids. So dysplasia meaning a shallow socket. Instead of a normal, curved socket, the socket's shallow. And so the ball can move around more in the hip. And micro instability is a newer diagnosis that we're learning more and more about by the day. It's a low level of sort of dysplasia to some effect. Arthritis, of course, is common in older patients and is in the front. Sports hernias, which we now call poor muscle injuries, are common as well. And then lateral, so out on the side, most commonly around the greater trochanter. You can palpate the bone on the side of your hip there. So FAI sometimes gives you pain on the side. But slightly less common. More common are things related to the greater trochanter there, which we now have lumped into the term called greater trochanteric pain syndrome. It used to be thought that it was just bursitis on the side of the hip. It's the other kids that that's not really true. It's not just bursitis. I'm watching a lecture now. Usually. No, okay. Maybe later. Could you please mute your line? It's usually somewhere on a spectrum, bursitis may be there, but that may be the smallest factor and the least common. The reality is it's more related to the gluteus medius tendon and gluteus minimus attaching to the greater trochanter. And tendinopathy there seems to be truly, when you look at the basic science of that area, that's really where the issues are. And it's a spectrum of just tendinopathy, partial tears of the gluteus medius and even full thickness tears of the gluteus medius. We now call the gluteus tendinopathy the rotator cuff of the hip because they really do have a very important role. And now we recognize more and more when there's tears there. An external snapping hip can happen on the side. That's when the iliotibial band snaps over the greater trochanter. Posterior, the most common thing is usually related to the spine, whether that's the lumbar spine or the sacroiliac joints, SI joints. That's common posteriorly. Now many people come in saying they pain the hip and it's really toward the back of the hip. And so greater trochanteric pain syndrome again, more commonly on the lateral side, but sometimes people feel that pain in the posterior. And there's a few other less common things which are deep gluteal space and ischiofemeral and it's outside the scope to talk about these other things, but there are less common things that can give people pain in the hip posteriorly. But here's sort of the most common. And this is how I deal with it and how I try to figure out what's going on in the hip. Because the hip's one of the things where the physical exam, the history are really important in it and it can be hard to figure out what's going on in the hip. Many of these patients have seen multiple providers before they get to me or someone else like me who specializes in this, because it can be hard. It's hard to figure out sometimes what's causing the pain. So we'll go into the labor more. So the labrum is a ring that goes around the edge of the socket. So this green is sort of the cartilage in the hip and the rim around it is where the labrum. You can see the labrum is a triangle that extends from the edge of the acetabulin and it's indirect continuity with the cartilage. So in this view, this is with the femoral head removed. It's a horseshoe shaped. There's a ligament called the transverse acetabular ligament that connects it at the bottom. But in cross-section it's triangular. So here it's one of the earlier microscopic studies which the studies on everything about the hip are actually not very old. This is 2001. So most of the research in this is in the last 20 years. But the labrum is triangular. This is the articular cartilage. It forms its direct continuity with the labrum. And the joint, this is the joint side, the femoral that would be here. This is fibrocartilage that is in direct continuity with the hyaline cartilage of the hip. And the important thing is that there's sensory nerve fibers in the labrum. So when there's a tear in the labrum, when it actually develops, there are nerve endings. So that's why people can't have pain from a tear at it. Unlike the articular cartilage, there's no nerve fibers there. And so when they have pain related to the cartilage, it's usually pain related to the underlying bone. So here's another view of it. And the role of the labrum, the more research into it, the more we know. And it gives you a little more surface area because it extends the cartilage out. So it gives you more surface area for the ball to move inside the socket. It also forms a suction. So the hip is actually on suction and there's negative pressure in the joint. So the labrum forms a seal to keep the fluid. There's about a milliliter of fluid in the joint and that labrum keeps a suction to keep the fluid in the joint. And it maintains the negative pressure in the joint which is important for stability in the hip. We think that the hip is innately stable because it's a ball and socket. The reality is there is microscopic motion of the hip and too much can be pathologic. So the labrum is important in that stability role and maintaining the negative pressure in the hip. So we know that tears in the labrum happen for specific reasons. And the first study that looked at this in 2004, 90% of patients had a bony abnormality for the tear. So these are people that had confirmed labral tears on surgery, 90% of them had a bony abnormality. And so it can be from different things. FAI, which I'm gonna go into more to really describe it and explain it, but other things, so dislocation. So the hip dislocating completely out of the socket which happens from a big injury, a car crash or something high energy in a sports injury. When the hip dislocates, it can tear the labrum, no question. Displasia meaning the socket's too shallow instead of it being a nice curved socket, it's too shallow, meaning the ball's moving around too much in there. That extra motion can tear the labrum. And then now more recently in the last five years, probably we've learned more about microincibility. So just microscopic extra motion in the hip can give you more susceptibility to a tear. And something like Illar's Danlos Syndrome where people are ligamentously lax may get this more commonly. So they're real flexible in general and it may give them more motion in the hip. So this is what FAI is. So this was the first picture that everyone references for when FAI was sort of described. So on the left is the cam. So the cam is the extra bump of bone here. So instead of it curving in, it sort of sticks out and goes straighter down. And so this is abnormal bone. So when the hip flexes up, that extra bone hits the edge of the acetabulum, the edge of the socket and it hits the labrum. Here's the triangular labrum at the edge of the acetabulum and it pinches that area. And you can see that it hits the labrum but it also hits the cartilage. So the problem here is it causes a tear in between the cartilage and the labrum. And I just said that the labrum provides a seal to keep this all in continuity. So when you disrupt between the cartilage and the labrum, you lose that seal. And so that potentially is a big problem for the hip. Pinsar impingement is the other kinds. There's two kinds of FAI, cam and pincer. So cam is more common. Pinsar means that the socket sticks down more. I'll show you some pictures. So instead of, you can see where the socket ends, normal. This would be the socket sticking down more. And the problem with that is when the hip comes up, there's no extra bone on the ball side. So it actually hits down on the femoral neck, hits that extra bump of bone. And the classic issue here is that you get injury to the cartilage on the opposite side because it's levering on the neck here. Now this clearly is gonna injure the labrum as well but you can also get cartilage on the opposite side that's injured. And so here's a typical cam lesion. So instead of the ball curving in, it sort of sticks out here. And this patient, they have it on both sides which is very common in people that were athletes when they're young. I'll tell you why soon. And here's pincer. So pincer means the socket sticks down too far. So it sticks out to the side more and sticks down more. Now this person has both. They have a cam. You can see how this comes down instead of curving in. And so they have both. So you can imagine you'd really get these two bumping into each other early on when the hip is flexed. Displasia, which I've mentioned means the socket's too shallow. So here you can see that the socket doesn't curve down at all. It actually is sloping upward. The other thing that you notice about this is that more of the ball is sticking outside the socket. And so that means this femoral head is gonna move around much more in the socket than otherwise. And so this is a big problem. This leads to rapid arthritis. And the treatment for this is actually an osteotomy of the pelvis, cutting through the bones of the pelvis and reorienting the socket so that it sticks down more and so that it covers up the head to keep the femoral head in the socket. And these patients, if this is not treated, this turns into arthritis as early as late 20s. And so dysplasia can be a disaster much more so than FAI or impingement and all these other things. So this is the one, when we see this, we know this needs to be treated. The surgery for this to correct the socket can actually dramatically change the natural history of this disease. And this can delay a person from, instead of getting arthritis when they're 31 years old and needing a hip replacement, they could potentially be delayed till their fifties, which is a huge change in a person's life. So that can be life altering for sure when we pick this up. This is a microinstability. This picture is showing the physical exam, so you bring this hip down into extension and rotate the leg inward.  But what microinstability is, is a subtle increase in the motion within the acetabulum. And it can be caused by different things. So dysplasia, if it's not truly the full on dysplasia and the socket's just a little shallow, they can have this. Connective tissue disorders like illers-danlos, you can get it as a result of injury where the ligaments of the hip get injured. We see this among ballet competitors and athletes. And so they will, because they're so flexible and because they stretch their hips on purpose, they can actually stretch their ligaments pretty extreme and can get instability. It happens iatrogenically from having surgery on the hip. When hip arthroscopy first came out 15 years ago and people were still figuring out exactly how to go about doing it the right way, we know that some people got instability in the hip from cutting through the ligaments of the hip to get inside and then not repairing them afterwards. And there's reasons we don't know. There is idiopathic cause. So here's the FAI again and here's how we measure it. And so the more this bone sticks outside the perfect circle, the bigger the cam lesion is. So it's at the femoral head neck junction and we have this alpha angle that we use to measure it. It's, sorry, it doesn't project great but the issue with that is they have less offset between the neck and the front of the femoral head. And so it's gonna cause earlier contact with the socket and the labor. And so we use the x-rays to try to get a three-dimensional picture of where this bone is sticking out. And so every x-ray angle shows us a different part. Now the cam lesion occurs enterolateral. So 12 o'clock up at the top here, this is the lateral edge of it. You know, here would be more anterior which is brought out by these rotated x-rays. And so those show us the more anterior lateral bone and that's where the cam lesion is. So that's the logic behind the x-rays. So how does this cam bone occur? And there's lots of evidence that points to this being a developmental thing. When the feces is open in children, this is the fecial scar, this white line right here. So this is the open growth plate in kid. And when kids are playing lots of sports or being very active, they put a lot of stress through this growth plate. And so the thought is that the bone that forms here abnormally like in the lower picture is formed by a reaction to the stress going through the growth plate. And that theory has really been brought out by lots of studies that have compared the sizes of cam lesions and whether there is a cam lesion or not in patients who are active growing up or not. And there's actually a market difference. People that played sports and were active when they were young have much, much higher incidence of having a cam lesion in general and also having a bigger cam lesion to the point of being 60 degrees, the average alpha angle in athletes and 47 and not and having a cam lesion 64% in kids that played sports young versus 40%. So it really does point to this being a developmental thing. So meaning FAI cannot be caused in someone who is still developing, still has open growth plates. They don't even have this abnormal bone yet. So this, the condition of FAI really starts in the later teens and most patients complain about pain in their 20s and 30s. Probably when it's repetitively caused enough damage to tear the labrum and cause some issues. Pinser can happen sort of two different ways. So I said pinser is where the socket sticks too much down the end. And so this shows what's called a crossover sign which means that the acetabulum is rotated. So the acetabulum supposed to put point anterior just barely, but actually in some patients everyone develops different. And you can have a retro version of the acetabulum meaning it's pointing more posteriorly. And what that results is in the front now the socket's sticking down because it's rotated toward the back. So these are some of the things that we look for on this. And you can have global pinser meaning the socket is just really deep. So the socket edge sticks out because the whole femoral head has pointed more medial. And these are more common in people as they get arthritis but these abnormal conditions like protrusion now the socket's really sticking out far. The pinser is slightly confusing for us and hard to figure out how best to treat because even though the socket has different shapes if surgically if we try to change the shape of the socket or remove bones so that you don't have a pinser and so that it's not causing impingement you can actually remove cartilage which would be bad because then you're changing the cartilage surface of the hip. We know in any joint if you remove cartilage you increase the stress on the rest of the cartilage in the hip. So this study did some 3D CT scan and really showed that even though the sockets were maybe retroverted or deep they didn't always have increased cartilage. The cartilage amount stayed the same until you got to this real dramatic pinser that was a protrusio. And so because of this study we've treated pinser lesions much less and less because we're worried about overloading the cartilage and causing people arthritis. So we're much more conservative in general about pinsers than we are CAM lesion. CAM lesions can be treated surgically much better. Either way with the impingement we generally treat people without surgery first. The other interesting thing about FAI and hip impingement is that many patients have these findings on X-ray or a labral tear on an MRI and they don't have any symptoms. So just because someone has a CAM lesion on an X-ray if they had an X-ray of their pelvis for some other reason and you saw a CAM lesion or you saw a pinser it doesn't automatically mean they have FAI. They may have no pain in their hip. This study looked at 2,000 patients that had X-rays that didn't have any pain in their hip and you can see in people that are athletic 55% of people had a CAM lesion. So just having the X-ray of a CAM lesion is not a problem. It's when patients are having pain and we think it's coming from the hip that it's an issue. Same with pinser. Pinser in the general population is really high, 70%. Pinser is a little harder because everyone measures it differently so we don't have as consistent a definition of it. We do have angles that we measure but people measure it differently. Labral tears on MRI are as high as 70%. So if a patient has an MRI with a labral tear it doesn't automatically mean they have an issue and it doesn't automatically mean they need surgery. Now, we're happy to see these patients and I always do, I see many patients with labral tears but they're doing just fine and it doesn't mean they have to have a surgery because they have a tear in the labrum. The reality is that probably the MRIs are just so good nowadays that you see things that are just not symptomatic and we don't operate on something that's not symptomatic. So just having the imaging findings is not a disaster. The problem with FAI is that it can lead to arthritis. Having FAI does not automatically mean the patient will get arthritis but it is one cause of hip arthritis. And we now know that this in the last 20 years this has been figured out that this is one reason why people get hip arthritis. Dr. Gans is the first person that figured this out and he's famous because of this and lots of stuff he's done around the hip. But he did lots of hip surgeries and he realized over time, he just started noticing that people with arthritis had these cam lesions and had these pincers and when he finally looked back at 600 surgeries he was able to publish this landmark study that showed it correlated with getting arthritis. And so it can cause arthritis but it doesn't automatically mean it will. And if it has started to cause arthritis the problem is we can't stop it then. So we know if we operate on patients that are already getting arthritis, we cannot stop that. So the tricky thing about all of this patients with hip pain that are young is we're trying to catch them with these issues that are causing them pain before it causes too much damage. If they don't have any pain, it's fine. We don't have any evidence to say they're gonna get arthritis but if they're having pain from this then it may lead to arthritis and if it leads to arthritis we then cannot do a surgery to preserve their hip. At least we don't have any evidence of that now. So in general, when patients already have cartilage damage or arthritis, it's likely too late to do a joint preserving surgery. Hip arthroscopy, minimally invasive arthroscopic surgery for the hip doesn't work when patients already have arthritis. We're trying to catch it before to make them feel better and potentially decrease their chance of arthritis down the road. We don't know that for sure but we think we can decrease it. So this is the algorithm. So because FAI and this cam and pincer is confusing you have to have three things to have FAI. You have to have symptoms of pain classically in the front of the hip near the groin. Many patients will have clicking or catching or the feeling of giving way. You have to have physical exam findings that either needs to be restricted internal rotation or pain with fader which is flexion, adduction, internal rotation. That's a classic physical exam. There's many other physical exams that you can do but honestly you really only need to check their internal rotation and the fader. And if they have pain that points to them having pain in the hip and it points the physical exam toward the pain that they're telling you about and then having the x-ray. So if you have all three then you have FAI. If you have two of the three then you don't. If you have one of the three you don't have FAI. So you have to have all three of those and that is the triad for FAI. Pain, physical exam and imaging. Now we can do diagnostic injections so injecting lidocaine into the hip to confirm that the pain is coming from in the hip and we do that when we can't tell for sure if the pain is coming from the hip and then we can get MRI and CT scans for other reasons. The MRI looks at other things. Soft tissue, the cartilage, it can tell us some other stuff about the hip but we don't need it for every patient. And then both operative and non-operative treatment are options for FAI. And in general we start non-operatively because it works for many patients and I take care of many patients every single day with FAI and the minority of them end up needing surgery. Most of them don't need surgery and it's the minority that end up do needing surgery. And that's arthroscopic minimally invasive surgery. We will repair the labrum and remove the extra bone. So here's what MRI can show you. So it's good at finding the labral tear which is right here, this white line going through. This is the labrum, that's the acetabulum. It can show you cartilage damage and subchondral edema. So this gray lines the cartilage and then you can say you sort of lose it here and you have white edema in the bone. So there's already some cartilage damage in this verse. Here's avascular necrosis which classically looks like this lesion right here. Every once in a while we'll find a tumor. So honestly, when we are getting MRIs, we are ruling out other things that could be causing pain. And every once in a while I will see a tumor. And then stress fracture. And this is the number one reason that anyone, if anyone's doing primary care and seeing patients with hip pain, if you're worried about a stress fracture, you should get that. And like I said, stress fracture usually happens in someone who's recently picked up running or has increased how much they're running. And then they have pain with weight bearing and pain with running to the point where they stop. And so this you should get an MRI right away because we can prevent this from turning into a true fracture. If we keep them off that, this will heal and they don't have to have surgery and they won't break their hip and you just have to get them off it right away. So stress fracture, when there's concern, we get MRI right away and you can get that improved from the insurance company every time. So the treatment, like I said, can be both nonoperative and operative. And in general, I treat everyone without surgery first for labral tears and FAI. And the reason that physical therapy works is because one of the problems with FAI is that the tilt of the pelvis changes when the impingement happens. So this study was very interesting. They did some sort of cadaver modeling of the pelvis moving and they showed that just if they tilt the pelvis 10 degrees anteriorly, it really changes the range of motion and it causes impingement much, much earlier in the motion. So tilt the pelvis 10 degrees anterior and you get 10 degrees less of hip flexion before that occurs. And that's actually pretty significant. 10 might not seem like a lot, but patients will notice that easy. And then five and eight degrees in limitations and internal rotation. And anyone in their 20s, 30s, 40s, 50s, they notice these differences and that they can't move their hip as well. So physical therapy can change your pelvic tilt and that can really increase their motion and stop the impingement from happening because the mechanics are better in the hip now. Just because the bone is there doesn't automatically mean it's gonna be a problem. You can have camel lesion, but if the mechanics are good, it may not impinge. Surgery for this works too, just to get an appreciation for this, 2008 and 2009 were when the first real studies of at least 100 patients came out for hip arthroscopy. So this has not been around for very long. And these were the early studies that showed hip arthroscopy works. Now in 2018, the biggest study yet, that's a meta analysis, looked at 31 reasonable articles that had a fair number of patients. And now we see that PROs, patient reported outcomes are improved in all of these studies. So the surgery does work. Repairing the labrum is what we wanna do, not debriefing it. You don't wanna just remove the torn labrum, you wanna repair it back down to the bone. And we know that we have low re-operation rates, only 5%, only 1% complication rate. So in general, it's pretty safe and pretty effective. 2019 with more sophisticated stuff where we look at the minimally clinically important difference. In this two year study, they showed 73% of patients had achieved a minimally clinically important difference. So the majority of patients are getting better. Now in this study, they had some patients with arthritis and things that we know are failure risks. And so if you eliminate, you can't eliminate workman's comp, but you can eliminate arthritis and BMI is questionable whether you can change that. And so the reality is if you decrease arthritis, you can get your rate of success even higher than that. And most people think it's probably 85 to 90% successful the surgery nowadays. So there's been three randomized controlled trials comparing surgery versus no surgery. One from the UK in 2018 published in Lancet, 170 patients in each group. At one year, they showed that surgery patients had improved more than without surgery. People improved in both groups, but it was the minimally clinically important difference advantage of surgery over no surgery, but both worked. And then in BMJ in published in 2019, just over 100 in the physical therapy group, non-operative treatment, both improved again. The PT in this did not improve that much. The surgery improved significantly more. So this one also favored surgery. And then the third and probably the worst study of all, only 40 patients in each group was done in the military here in the US and they had an issue with crossover. So 28 out of the 40 patients in the physical therapy group didn't do physical therapy and actually had surgery. So basically you had 68 out of the 80 patients in this study ended up having surgery and they found no difference between groups. But it's really not, this turned out to be not a great study. And in this, this is the only study in the literature where patients felt the same after the surgery. And so that sort of clued us in that there's something wrong with this study because there's been 31 other papers published to show the success of hyparthroscopy. So no one's sure why this turned out like this. And there's many theories because it was a specific patient population in the military that they don't know why this turned out. Returning to sports is great, about seven months to get back to playing the sports and 85% of patients can get back to playing the sports they want. Smaller study about running 94% of patients got back to running at eight and a half months. So it does take a little bit of time to recover from these, but people do recover. And then lastly, comparing males and females, which this is important to do in our studies because we don't know if there's innate differences in how people recover from surgery. This specifically looked at elite athletes, but regardless, the men and women returned back to sports at the same level. So that was also a good thing.


Hello, Matt Rabel here at KubeCon, coming to you live. Jonathan Whitaker, I work on the Fine Grain Authorization Project here at Okta. So it's called OpenFGA, is that correct? Yeah, OpenFGA stands for Fine Grain Authorization. OpenFGA is our open source operating unit. And what's your favorite feature in the OpenFGA project? I actually love our attribute-based access control feature that we just rolled out. It brings more expressive capability to OpenFGA, allowing developers to express more complex policies involving attributes of arbitrary data. So it's extremely powerful, very expressive, and it was a lot of fun to build. And what excites you about the future of authorization? You know, authorization is kind of, it's up and coming. We're kind of stuck, like, authentication about ten years ago, authorizations like there. And there's a lot of fun opportunities for so many integrations, so many standards, and just improving the application developer experience with security and making our applications have better off. More Fine Grain Authorization.


I'll now hand over to Wesley on behalf of the Ulster Farmers Union, thank you. Okay thank you Chairman. Again we appreciate the opportunity to be down here today to talk to you and thank you very much for the invitation to do so and can I apologize to the outset for my present Barclay Bell being otherwise engaged today, otherwise he himself would have been down here so unfortunately I have to put up with me in the meantime. And I suppose I would like to just cut the chase in terms of Brexit where are we now and then go back and revisit some of the issues and I think what I'm able to say today is different than had it been done here by two or three weeks ago and I'll come on to that as to why. I think it really fits in terms of politics, process, timescale and the whole uncertainty around that. Back at the end of March the UK triggered the article 50 mechanism. The European Union immediately came back with its outline for negotiations and the three cures as Joe's already outlined in terms of people's finances and the whole issue about the Irish border and they also said that they needed all that sorted before they then moved into the whole issue about where the UK would fit within a prickly trade going forward and that was going to take a significant bit progress before they entered into those discussions. We have had a UK general election on the 8th of June and we already have now had a Queen's speech as of a couple of days ago outlining just exactly where the UK government intend to be over the next couple of years in terms of implementing particularly a large number of Brexit-related bills. The EU-UK negotiations started officially on Monday and you've obviously seen those at a very high level in terms of the coverage that they've got and of course the comment was made earlier about stable government and unfortunately in Northern Ireland we don't have that. We had a government sort of failed by the wayside, they were re-elected, we haven't formed anything and we have until Thursday of next week to try and form something again and unfortunately probably we're hardened politically in terms of our nationalist Unionist lanes as we've seen. Having said that I suppose the big advantage in all of this which is going back to my earlier point about why I may be able to say things differently now than I would be three weeks ago is because we now have a minority UK government who are depending on not only our Democratic Unionist Party in Northern Ireland but also a number of Scottish Tory MPs who didn't exist previously and I think going back to the key issues to why we're all here in relation to Brexit that certainly makes things a lot more different than we in terms of where we're going, where we would have been otherwise had the Conservatives got the landslide majority that initially looked as though that was going to be the case in terms of maybe some more scope for a much softer Brexit than would have been the case otherwise but then as the issues about the process around how that would be delivered. That's where we are as of today. In terms of the issues this time last year obviously the referendum that might come was known, bit of a shock to everybody. The EFU we are criticised as the way we not nail our colours to the mast at the time. It was very clear from discussing it with our membership that there was a complete spectrum of views and obviously politics came into play as well as just the agri-freedom industry. So we decided that in the absence of any compelling reason to leave we advised people to remain but we recognised that each individual had their own right to vote as they saw fit. We then after the referendum pulled together our main policy committee chairman vice chairman and in July of last year come up with 10 key goals across four themes. The four themes were trade, support, labour and regulation. Obviously different elements of those had more or lesser effects in terms of us in the farming industry. If we can just deal with those fairly quickly. In terms of trade the goals we identified, sorry the UK government's goals were that we would be leaving the customs union but that they wanted a deep and special partnership with Europe going forward and that was in the article 50 letter that the Prime Minister wrote. There is a recognition at a European level and the data at the UK level that the ROI-NI border needed to have flexible and imaginative solutions would be required was the phrase used, sounds wonderful. But that we also recognised that trade would have a major impact on the amount of support that the Northern Ireland agri-food, indeed the UK agri-food industry would actually require going forward so it was a starter in all this. In terms of agriculture support we have depended on the common agricultural policy for the number of years we've been in the European Union and I think it goes without saying that to be honest we have largely depended on both the French and the Irish governments in terms of delivering that support for agriculture going forward. The UK government always made it very clear that the CAP was something that it considered to be a waste of money and that they wanted to do things differently so we now have a different scenario where we now have to convince the UK government, the UK wider public that we are worth supporting. So in terms of agriculture support we get around about £300 million sterling into the Northern Ireland farming industry every year. That is guaranteed both this year 2017 and next year 2018 while we're still part of the European Union. We in theory will be left it by March 2019. We apply for our basic payment scheme as you folks do down here. After that date it will be May 2019 so we will not have a system to apply to as it stands if we have left the European Union. But immediately after the referendum the UK government did come out and guarantee the equivalent amount of money for 2019 which would have been the last year of the CAP had we remained in the European Union. But there was a big question mark as to what happened beyond that but equally the CAP was up for renegotiation anyhow and it was only guaranteed to 2019. So agriculture is a long-term business and we always wanted to make sure that we had some degree of certainty going forward. So we were pleased that in the Tory manifesto this prior to the election they at least committed to guaranteeing the equivalent amount of support up until the next Parliament. At that stage they thought the next Parliament was going to be 2022. It may well be the next Parliament could be a lot sooner than that now but we don't know. But at least it's in there and they have the only party to really commit to that extent. We have an issue it's one thing securing a pot of money and securing it for a number of years going forward. We obviously want to make sure that Northern Ireland maintains its share of that UK pot. Historically we actually have about 10% of the UK single farm basic payment scheme and that's based on the fact that we have a lot more small intensive livestock farms which generated the money from which the basic payment scheme was created. If you look at the Barnett formula which is how money is generated from Treasury across to the regions of the UK we only get about 3.3% so that would be an immediate reduction of almost 66% in terms of that 300 million 200 million pounds which is a big chunk of money bearing in mind as Jules rightly pointed out. Without that we're actually losing money even with it we're losing money so we need that money going forward for not just Northern Ireland farming Northern Ireland agri-food industry but the wider economy and rural areas of Northern Ireland as a whole. So we have to recognize that if we do get this pot of money then it has to be a different delivery system. The UK government always made it clear the CAP wasn't the right way to go. We ourselves don't necessarily believe it's the right way to go because we feel it was always moving more and more away from activity in terms of both production activity and environmental activity and you are basically getting paid just effectively like an income subsidy just to be on the land. So we feel that there is an opportunity to actually move towards a different delivery system that is an issue about what sort of transition we need going forward and of course as I mentioned earlier about the potential to regionalize within that as we actually have within the CAP at the minute where Scotland Wales Northern Ireland they can all do slight variances along a common theme. We needed to make sure that we didn't actually all have different policies going forward in the UK and obviously our land border with the south of Ireland we've always noticed the differences and the impact that would have. So we needed to make sure that there was a UK framework going forward and the discussions on going about that and we're pleased to see it in the Queen's speech a few days ago she did actually refer to the fact that there would be an agriculture bill but again we have to get into the detail of that. So as far as the EU is concerned prior to the election there was a very significant amount of activity in terms of developing some sort of future domestic agriculture policy not just for Northern Ireland but for the UK. We published a document, launched it at our Balmoral show in May, have since met with a large number of both agri-freed industry stakeholders and indeed environmental stakeholders and we're still engaged in those meetings. We're going around our membership starting next week around meetings in Northern Ireland just to talk about both this and the whole issue around trade and that is very much ongoing and we will certainly be engaged with our counterparts across the GB in relation to that. Those are the two big ones as far as direct impact on the farming industry is concerned. In terms of regulation this was always a case of just simply farmers themselves weren't necessarily annoyed at the regulation they were annoyed about the enforcement of the regulation and the fact that it was linked to their direct subsidies in terms of their basic payment scheme through cross compliance and that was the thing that really annoyed them so it's not necessary the legislation itself or in fact the standards associated with that legislation. Our customers or supermarket customers actually require higher standards and I think from our perspective we see Northern Ireland as a small flexible region and we can possibly do things that actually increase our standards and if we get the proper support for the industry going forward then we can move in that direction. We already have electronic identification in for sheep and that hopefully gives us some sort of unique selling point its traceability and we're looking at can we do similar type mechanisms going forward. So in terms of legislation say we didn't necessarily see it there were going to be any change in the standards but maybe the way that they were linked to that direct support was the critical thing in terms of enforcement. That's really the regulation issue. The final one is labour and it was always recognised that from a farming perspective unlike our counterparts in Great Britain who depend at a farm level very heavily on non-British labour particularly in terms of the vegetable and the fruit sectors. It wasn't as big an issue for the Northern Ireland farming industry having said that it is still an issue but it certainly is a major concern for our processing industry who have anything between 30 and 65 of their employees as non-British nationals. So it's very much an important issue and we are pleased to see that obviously this is one of the key things that the UK government are already moving on to try and give certainty to those that labour force that they are wanted and that we don't necessarily want to remove them from the UK. So if you like those are the very broad issues. In terms of trade specifically which I know is the whole issue about the North-South situation obviously as Joe's already pointed out there's milk comes south there's beef comes north there's pigs comes north there's lams go south and we are very heavily integrated in terms of movement back and forward across the border. We at the outset as an organisation as part of our 10 key goals identified that we wanted to maintain access to the European markets and also that we wanted to ensure that there was minimum disruption between Northern Ireland and the south of Ireland in terms of that trade. We did however also want to see if we could secure additional markets outside the European Union but we can back that later on in discussion. We did also stress the importance of making sure that standards were not undermined and the whole issue about the external tariff in terms of not only just the actual amount of money but the standards that have been met I think that's critical going forward because you don't want to be undermined by lower standard product. So in terms of specifics around trade Northern Ireland has small region but the agri-food industry is important. We have grown our output in terms of our sales over this last while and we've increased that by 42% in terms of what remains in Northern Ireland. We have also seen our growth to the south of Ireland increase by it's over doubled between over the last 10 years but nonetheless when we look at the actual hard figures and there's only somewhere in the region of milk and beef in particular where there's issues about product coming or sorry milk in particular with product coming going to the south of Ireland is probably the key issue going forward. At the UK level we're not self-efficient in Indigenous products primarily and the latest figures we have show that in pork the UK is only 55% self-sufficient, beef 75, lamb 92%, poultry 73%, butter 75, cream 95, yoghurt 75, cheese 55, milk powders we don't do a big run in the UK so it's 200% self-sufficient but that goes elsewhere. So the UK is not self-sufficient in what it needs for its consumers and obviously the UK population continues to grow. The actual trade imbalance that the UK have in particular the meat products there's somewhere in the region of a £1.6 billion annual gap for poultry meat, an £800 million gap for beef and lamb, a £600 million import gap for dairy products and a £1 billion gap for pig meat, that's annual so there's very huge gaps in terms of self-sufficiency and the imports versus exports. That's really as much as I want to say at this stage I hope I have wetted your appetite for a bit of discussion later on and certainly we are very keen that over the next few years we try and make inroads into making sure that we have maintain as much of the status quo as we possibly can do and I think that's where we're all on at this particular stage so thank you very much indeed.


see when you deal with the when you deal with the variable force okay one very common variable forces the spring force fine so it will be very common to find the work done due to the spring force later on fine so since we will be dealing with the spring force or the work done by the spring force multiple times so let us just derive the expression for work done by the spring force and then we can directly use the expression for work done by the spring force okay so we are trying to derive the expression for a very common type of variable force which is the spring force right down work done by spring force okay or work done by spring all right so let us say that there is a spring with a spring constant k spring constant is k fine initially the spring was extended from its natural position it was extended by a value of x1 and finally it got extended to x2 fine so the spring is getting extended from x1 to x2 you need to find the work done by the spring when this process happens okay try to do it spend some time it's a variable force right and you know that the force because of the spring will be k times x okay and this force direction is opposite to the direction of change in x sorry the force itself depends on change in x so force is k delta x you can put a minus sign like this so force is equal to minus of k times x fine now work done if you suppose displace this spring by dx okay you further extended by dx so the displacement will be opposite to the direction of the spring force right so you can write the work done as minus of kx dx fine where x is the change or x is the so to say from the natural length how much it has deviated that is x okay so if the deviation increases by dx further that the work done will be kx dx and we are talking about a negative work done by the spring here because the force of spring when your displacement is this direction will be in opposite direction because the spring is already extended fine so this is the small amount of work done total work done will be an integral of this and k is a constant fine if k is not a constant it will not come out of integral so we can make a numerical in which k also depends on x fine but right now we will take a generic case k is a constant let's say its extension goes from x1 to x2 right so this will be equal to minus of k by 2 x2 square minus x1 alright so the work done okay Sukirt is asking why it is negative okay so we are taking a case in which the spring is extended already fine and you are further extending it right so when spring is extended this side the spring will apply force in that side and you're further extending that side so force will continue to act in backside so there is 180 degree between force and the displacement so that is why it is negative okay so this will come out to be half of kx1 square minus half of kx2 square fine so this is the work done by the spring alright now you're going to see something which is very unique to the spring suppose initially initially spring was compressed fine it was compressed by x1 right and then you are extending it now it is extended by x2 right so compared to natural length the spring initially was in compressed state and compared to natural length spring now has an extension of x2 okay so in this process when you go from 0.1 to 0.2 now what is the work done by the spring can you try it your own is the compression equal to extension see compression is right now x1 and extension is later on x2 okay bar that is not correct Sukirt no no Sukirt hmm others let's try it all on yes bar it will come out to be same the work done by the spring is same okay let us see how we can do this particular case see right now the spring is compressed it is compressed by x1 let us say that it goes to natural length this is step number one to step number two from compression it goes to the natural length and then it get extended fine this is this dotted line is natural length so this is x1 and that is x2 right okay now from one to two the work done is positive because the spring will try to push in this direction and the displacement is also in that direction so work done will be positive from one to two so let us say work done is w here and w two there so total work done will be w1 plus w2 fine let us try to find out work done w1 and w2 separately so w1 work done will be integral of kx dx the limits of x will be from x1 to 0 okay it will minus will come outside it net net it should come out to be a positive thing alright because the force is always on the right hand side and displacement is also on the right hand side okay okay fine so this is equal to half of kx1 square alright now w2 is what w2 is minus of kx dx now x is going from 0 to x2 you will get here as minus of half kx2 square fine so total work done will be sum of this plus that so w will be equal to w1 plus w2 this will be equal to half kx1 square minus half of kx2 square fine so it does not matter whether this compression or extension fine so if initial write down if initially impression or any of it if it is x1 and finally compression or extension it doesn't matter if it is x2 then the work done then the work done by the spring will be half kx1 square minus half kx2 square fine it doesn't matter whether x1 is compression or extension or x2 is compression or extension fine all of you understood this work done by the spring any doubt anything please type in yes or no no it did not freeze niranjan no doubts okay so now i think only 17 people are there so we'll focus on problem solving okay so let us take up questions now but that doesn't mean that problem solving is lesser importance this is actually more important than the concepts assume there is a fourth see you see that at times the problems from this chapter can be solved by applying concepts from the neuter okay so you can solve the question in two different ways but the thumb rule is you should first try to solve using concepts from this chapter because you are dealing with scalars and second whenever they talk about finding velocity okay so try to use work energy theorem okay do not find acceleration and then from acceleration you find the final velocity so suppose there is a force of 100 newton applied here this is a block of 1 kg mass okay initially its velocity was one meter per second you need to find out the final velocity when this block got displaced by a distance of two meters all of you clear about it if you if you have any doubts please type in or start doing it okay there is a block it has initial velocity of one meter per second you are applying 100 newton horizontally fine coefficient of friction is 0.1 between the block and the ground all right when this block moves by two meters what is the final velocity of this block use work energy theorem okay don't use newton's law of motion concept to solve this because you're just learning how to apply work energy theorem root of 395 that's what Niranjan also got okay so see here basically you need to find total work done on this one kg block work done by 100 newton force work done by friction work done by gravity and work done by normal force all these work done when you add up will be equal to change in kind of energy that is half m into v square minus half m into u square I hope you all have got this particular thing work done by the 100 newton force is what 100 into 2 okay work done by friction is what first of all we have to find friction force which is mu times normal reaction normal reaction is what mg right so which is 1 into 10 so 10 newton's is mg so mu into 10 is 1 newton okay so friction force is 1 newton and good thing is we know the direction which is opposite to the displacement minus 1 into 2 is a work done by friction work done by gravity is 0 and work done by normal reaction is 0 because both of them make 90 degree with the displacement okay this is equal to half m is 1 so v square minus half m is 1 u is 1 so this is just half okay so v square by 2 minus half is equal to 200 minus 2 200 minus 2 198 okay so v square is equal to 198 into 2 plus 1 fine so this is 397 v square so v is equal to under root of 397 fine okay we'll take up one more question before you know closing this session any doubts on this message any doubts on whatever we have done just now we have simply applied work in ag theorem any doubts okay guys so let us move to next question I'll take up a j don'ts level question see we have learned everything that will take you I mean that will take to answer any question from this chapter okay although the definition of potential energy is something which we haven't done yet but then if you apply work energy you can solve almost every question okay so I'll just find out a question from previous here this thing I think online session like this is lot more efficient than the physical class otherwise you guys talk so much I waste my energy in just keeping you quiet you can type in your uh mess your your feedback on whatever I just said so what I will do here is that I'll just discuss with you the scenario initially and then you have to solve it yourself this is m and that is capital M by the way we have derived work energy theorem for a particular shushant I doubt anyways so we have discussed work energy theorem but that work energy theorem is applicable for a single mass right now okay so work done on mass one one change in kind energy of mass one right so this is mass m ones okay great so this is for mass one k one minus k two okay I am talking about mass one this is m one m one okay and suppose there are two masses in a system like in this particular scenario two masses are there then work done on the second mass will be equal to change in kinetic energy for the second mass I'm writing it in the wrong way let me correct it change is always k two minus k one okay work done work done on the second mass is focus on the question k two for mass two minus right now I'm discussing the concept okay I'll describe the question little bit later k one m two fine so these are the two work done on two different masses if you add up these two work done if you add basically two equations you'll get here k two for mass one plus k two for mass two minus k one for mass one plus k one for mass two okay now basically there will be some internal force between mass one and mass two right now the internal forces tension between capital M and small m fine so when you add up the work done separately like this work done by the internal force cancels out so this will be only this is work done by external forces so external forces what mg is the external force over here all right so total work done on the system okay it is change in kinetic energy of the total system the system may have multiple masses so change in the final kinetic energy of mass m one plus final kinetic energy of mass m two and so on minus you know initial kinetic energy of mass m one initial kinetic energy of mass m two so we just modified work energy theorem so that we can apply it for a system which has multiple masses okay now let us see what this question is about Bharat is in a hurry focus on the concept okay anyways a string with with one end fixed on the rigid wall so this end is fixed on the rigid wall passes over the fixed frictionless pulley so this is a fixed pulley through which this string is passing and this distance is two meters okay capital M has a mass of two kgs small m has a mass of 0.5 kgs all right now the string is horizontal that capital M this string is horizontal fine this one from here till here the string is horizontal okay and it is vertical from here till here so this string is vertical that string is horizontal okay you need to find out what will be the speed what will be the speed with which capital M will hit the wall when you release the small m what will happen this is small m will start moving upwards okay when this small m starts moving upward since the capital M is heavier the heavier mass tries to come down okay and when it comes down it will try to move in a circle like this and the entire string as I you guys try please first then we'll discuss the solution try it your own does it have friction otherwise where you see friction can be and there is no contact surface pulley is frictionless which is your usual case there is no surface contact so there's no question of friction knows okay the string is not cut see that this small m is very light so it automatically this capital M will go down and when capital M goes down this will move up this capital M is hanging in air right now are you guys clear about the question type in yes or no now try solving it this came in you know very very long back when you guys were not even born 1985 I was two year old that's a very valid question this distance the distance of capital M from the wall is one start solving the question for you forget what what is asked huh we have to find with what velocity capital M hits the wall okay with what velocity capital M hits the wall just write questions don't need to solve it and just message that you have written the equation then I'll write my equations you can compare message done when you're done with writing the equations oh somebody got the answer velocity root of 2.1 Niranjan I've read it hmm answer is 3.29 meter per second is that what you you guys are getting 3.29 5 root 5 is like can say 10 so root 10 is what yeah yeah so get close to that that's correct okay let us analyze the scenario I'll just analyze the scenario and see what it is when this block moves how it will move it will move in a circle so it will complete a quarter circle and hit here getting it so when it hits here the string becomes like this isn't it so now see what is happening this block comes down okay this block comes down and this block moves up suppose this is x the distance it moves up I need to find out the distance why because I need to find out the work done by gravity and for that I need to know what is the displacement right so this is clear how much capital M moves along the direction of gravity this is one meter only because the distance of capital M from this is one meter right I need to find out what is x all right so for that I need to first know what is this length this length is root over 2 square plus 1 square which is under root 5 fine so initially that same length was one meter and now it has stretched this distance one meter got stretched to root 5 right so the extra distance that is root 5 minus 1 this must have been coming from this end fine so this is the value of x all right now gravity is doing work on capital M as well as on small m all right so work done by the gravity on capital M will be mg into what into one all right because that is a displacement of capital M along the direction of gravity fine work done by the gravity on small m this is what now minus sign will come because gravity is acting down but this is small m is going up by what distance by x right so this will be small m g into root 5 minus 1 all right there is no other external force fine or you can say that this tension might you may feel it is external force okay which is correct also but then since we are saying that it is moving in a circle tension always remains perpendicular to the displacement so work done by this tension will be zero okay so total work done in the system will be work done by the gravity on capital M plus work done by the gravity on small m right this total work done will be equal to change in kinetic energy so if initial velocity was zero and final velocity is v1 and v2 you can say that kinetic energy is half small m into v1 square plus half capital M into v2 square where v1 is the velocity of small m and v2 is the velocity of capital M all right now we need to find the relation between velocity of capital M and velocity of small m all right now in order to find the relation between the velocities I need to use constraint relation here that the string is fixed length fine so string is of fixed length hence along the string relative velocity should be zero if along the string if there is any relative velocity it means that the length of the string is changing fine so if the relative velocity along the string is zero then what will be the scenario so for small m we are saying v1 is the velocity okay and for capital M we are saying velocity is horizontal because it is moving in a circle fine so after quarter circle it will try to hit the wall horizontally fine so if this is the angle theta fine and this is the velocity let us say this is v2 is theta I can say that v2 cos theta is the velocity component along the direction of string okay this should be equal to v1 all right and what is cos theta you have a nice right angle triangle here for which cos theta is 2 divided by root 5 fine is this how you guys have done it Krishna Sukheer those who got the correct answer is this how you have done this yes or no is this how you guys have done it okay anyways hope you have learned a few concepts from this particular question so in j advanced questions like these you can expect all right so today was just a basic session on introduction to work and energy all right so next class probably you know we will our focus is more our focus will be more on problem solving okay we'll start with the basic level of problems and then we'll build on it and we'll also introduce something which is called potential energy okay so we'll introduce potential energy and we'll see that how we can use potential energy in problem solving also okay at times you know in question itself it will be written that potential energy is this much so you cannot avoid potential energy at times all right otherwise if there is an open-ended question like this where there's no mention of using potential energy you can solve this particular question without using gravitational potential energy formula okay because you have work energy theorem which is more generic all right so thanks for joining in and that's it for today's class and I hope you have enjoyed today's online session the homework for for this class is you have to finish to finish objective one from hcverma at times you'll see some questions which for which we haven't done theory yet but that's okay you you try to do it still and then you have to solve at least 30 questions from exercise one okay so that is a homework for next class and come with all of your doubts and we'll discuss it first and then we'll continue with the session okay thank you