“I need a worksheet to go along with this youtube video. its on newtons first law of motion. here is the transcript: Introduction 0:00 Hi everyone, welcome to this class on Newton's first law of motion. I'm going 0:06 to make the first law of motion crystal clear to you. So I'm sure you'll find Newton's first law really easy after 0:13 watching this video. So guys be sure to watch the entire video. So welcome 0:18 everyone and I want to say that do check out our website manuchacademy.com. 0:23 We've got these awesome courses for physics, chemistry and maths for you. So 0:29 we we'll be launching the maths class 9 course for CBSC very soon. And we've got 0:35 these physics and chemistry courses. And guys, these courses are at a big discount right now. So do check out 0:41 these courses. I think you'll find them very useful. I'll put put the links below. And guys, if you haven't 0:47 subscribed to our YouTube channel, what are you waiting for? Do hit the subscribe button and do share it out 0:53 with your friends. And guys, can I get a like from each one of you here? So are you excited for this physics class on 1:00 Newton's first law of motion? All right. So welcome everyone and let's take a 1:05 look here. So before we start, I just want to do a quick recap uh that we discussed in the Recap 1:12 last class on force and motion, right? So you know what causes motion? The 1:17 answer is force, right? So guys, can you see in this picture the uh horse is 1:23 applying a force on the cart? That's how the cart moves, right? And this football 1:29 player or soccer player, he's applying a force on the football to cause it 1:34 motion. So remember guys, force causes motion, right? And you know that this uh 1:41 train, the engine of the train is pulling the train. It's applying a force, right? So force is absolutely 1:49 necessary for motion here, right? We know that force produces motion. That's 1:55 right. Uh Abhinav says force is defined as a push or a pull. Excellent. And 2:00 guys, Newton's laws of motion are all about force. So let's take a look at it. So here are Newton's famous three laws Newtons Laws of Motion 2:08 of motion. I'm sure all of you have to seen these laws and I'm going to make the first law crystal clear in this 2:15 video. So we are going to mainly focus on the first law. And what does it say? A body continues in its state of rest or 2:22 uniform motion unless compelled by an unbalanced external force to change the 2:28 state. And the second law you know it says rate of change of linear momentum of a body is directly proportional to 2:35 the applied force. So guys can you see this word force? It's all over the place 2:41 and it takes place in the direction of the force. Right? So Newton's laws of motion are about motion and force. And 2:48 the famous third law to every action there's an equal and opposite reaction. 2:53 And guys you know what are action and reaction these are also forces right so 2:59 Newton's laws of motion is all about force and we are going to do the exciting first law today and I'm also 3:05 going to talk about the concept of inertia. So let's focus on our first law. Right? Newtons First Law 3:12 So guys are you carefully with me? So please uh follow me carefully. Let's take a look at his statement. A body 3:20 continues in its state of rest or uniform motion unless compelled by an 3:26 unbalanced external force to change the state. Okay. So let's really break down 3:32 the statement and understand it. All right. So first let's focus on this part which 3:39 says that a body continues in its state of rest. Right? So first let's say a 3:46 body is already in a state of rest as you can see in this example this rock 3:51 over here. So can you see the picture of this big rock or big boulder right it's 3:57 already in a state of rest. So guys, can you see in the picture here? Right. And so what does the law 4:05 say? Say that it will continue continue to stay in its state of rest unless 4:12 Okay. So unless compelled. Compelled means forced, right? Unless compelled by 4:19 an unbalanced external force. Right guys? So guys, can 4:25 you tell me what is the meaning of unbalanced? Let's get these terms crystal clear. So what is the meaning of 4:32 an unbalanced force? So who can tell me here what is the meaning of an unbalanced force? So come 4:38 on guys, right? So what do you what do you mean 4:44 by unbalanced force? Unbalanced force means a force there should be the net 4:50 force should not be zero. So net force is not equal to zero. Right? So for 4:57 example, so what this uh thing is trying to say that if you apply a force here 5:03 then only you can move the rock or the boulder you can change its state of rest 5:08 right and the force needs to be external right yeah very good lot of you are 5:15 saying it's not balance force or the force or result of two or more forces which should not be zero excellent so 5:22 basically in short the net force should not be zero and here so if you apply a force right you need a large force 5:30 obviously because this is a big boulder you need a large external force to move it but this will be a so if I apply two 5:37 equal and opposite forces then what is this these are balanced forces right because they will cancel each other so 5:43 we are not talking about this because Newton's law of motion says unbalanced force please carefully look at this word 5:49 right so we are talking not about balanced forces which can cancel each other where the net force is zero we are 5:55 talking about unbalanced force and very important the force should be external 6:00 means the force should be from outside right so here the force you can see an 6:07 external force we're applying uh to this boulder to change its state of rest 6:13 right it's in a state of rest clear now let's take a look at the second part so 6:18 what does the second part say the body continues in its state of rest or uniform motion right so basically 6:25 Basically we are talking about two cases. The first case which we discussed was the state of rest or the second case 6:32 where let's imagine we have this tennis ball and you've thrown it into space. Okay. So you've taken this tennis ball 6:38 and you've thrown it into space here and it's already in motion. 6:45 Right? So the second case we are talking about is it's in a state of motion or 6:52 the law says state of uniform motion. 6:58 Right guys? So these are the two cases we are talking about. Okay. So let's say you've taken this tennis ball and thrown 7:04 it in space. Right? Then it will continue in its motion unless compelled 7:11 by an unbalanced external force. Right? So if no because you know in space 7:17 there's no friction also it's pure vacuum. So this tennis ball which is already moving will continue moving 7:24 continue moving forever unless somebody stops it. Right? Or some force stops it. 7:30 Right? Excellent. And guys what does uniform motion mean? So who can tell me what is the meaning of uniform motion? 7:38 Very good. I see Shri already has the answer. So guys what does uniform motion mean? 7:47 Yes. And uh Shir Hosur is asking in vacuum will the object move? Absolutely. 7:53 Right. Vacuum means there's no air. It's empty space. Nothing. So you know a rocket moves through vacuum. Right? The 7:59 earth is moving in a vacuum. Right? Because there is no uh because outside 8:05 we know in outer space it's pure vacuum. There's nothing there. Right? So absolutely motion is possible. Right? 8:11 You don't need gravity only for motion. Very good guys. Excellent. Uniform motion means same speed or more 8:18 correctly same velocity. Right? So let's write that down. So body continues in 8:23 its uniform motion which means uh let's let me write it clearly here. 8:30 So uniform motion guys means constant velocity. 8:35 Constant oops I wrote cost. It's a constant velocity, 8:41 right? So what does that mean? The speed is constant and the direction is constant. So let's say this ball is 8:48 moving at let's say 50 m/s in this west direction, right? So it'll continue 8:54 moving at 50 m/s towards the west, right? Until it is compelled by an 9:00 unbalanced external force to change its state. So Newton's first law is actually 9:06 very simple, right? It's basically saying if in simple words you can say a body remains at rest until you apply a 9:13 force or a body a moving body continues in its uniform motion until we apply a 9:19 force. Okay. So is that absolutely simple right? It makes sense right. So 9:24 guys take a look again. So a body like this rock will continue to remain at 9:29 rest unless we apply a force. And obviously know you know that for this large rock we have to apply a huge force 9:35 to move it right because there's otherwise friction involved. But if you have a small book still you need to 9:40 apply a force otherwise it will remain at rest. Right? So you can think a book lying on your table is in a state of 9:47 rest until we apply a force. Right? So that's what this law is talking about. Similarly now this is the more 9:53 interesting case. A body will continue in motion. Okay? A body will continue in motion 10:01 unless it is stopped by an external force. Right? So it'll continue moving 10:07 continue moving till a force right. So we have to apply a force like this to 10:13 stop the body or to change its state of uniform motion or to slow down the body 10:18 change the direction of the body. Otherwise this ball if there is no force so I'll erase the force. If there is no 10:24 force, the ball will continue to move like this in space forever and ever till 10:30 somebody stops it. Okay? So that is what this Newton's fundamental first law of 10:36 motion is talking about, right? We're talking about the first law of motion. 10:41 Clear? Excellent guys. Great to hear you guys are enjoying the class. And guys, please hit the like button and do share 10:48 it out with your friends so that we can have more people on our Manocha Academy family. Great guys. Lazy Body 10:54 So let's dive into some more details. So basically we say in other words we can say a body is lazy right right any body. 11:03 So here body means the rock we are talking about. So this body here is the rock and here the body is the moving 11:10 ball right. So here the body is the so it's the stationary rock and this moving 11:18 ball right and this rock which is at rest. And we say the body is lazy 11:24 because it does not want to change its state, right? It does not want to change 11:31 its state. Just like we feel lazy on the holidays to wake up, right? We are we 11:36 are feeling lazy to get up from bed, right? So we want to sleep more in bed. Similarly, the body is lazy, 11:44 right? Since it does not want to change its state of rest or uniform motion, 11:51 right? So rest it makes sense you know we can say the lock the rock is lazy because it's just lying there but even a 11:58 moving ball you can use the term lazy right because it just doesn't want to 12:03 stop or change direction or move faster or slower clear so the moving ball also 12:10 we can say it's lazy lazy in motion right lazy to change and similarly this 12:16 rock is also lazy it does not want to change and Guys, what is the science 12:22 term for this? So guys, do you know what is the laziness of a body called? So come on, I want all of you to try. What 12:30 is the laziness of a body known as? Excellent guys. So I see Amit has the 12:35 right answer, right? Uh Already very good. Excellent guys. Uh T 12:42 pratab saying superb. So the right answer for this is what is the laziness of a body called? In science there's a 12:48 word it's called inertia. You might have heard of this right? So inertia means 12:54 laziness of a body. Very important. And that's why we say Newton's first law talks about this laziness or inertia. So 13:02 Newton's first law is also known as the law of inertia. That's another word for 13:07 it. Right? So it's excellent guys. Superb. Lot of you are saying the word. 13:13 So inertia you can say in simple words. I just want to make the concepts of physics super simple for you. So just 13:19 remember this word laziness, right? Laziness of a body whether it's at rest or in motion. Excellent. 13:28 So this is how we can summarize, right? What is inertia? It is the property of a 13:33 body. It tends to resist a change in its state of rest or motion. Remember there 13:40 are always two cases, right? the state of rest or motion, right? So, inertia is 13:46 basically the laziness of the body, right? And the rest example is easier to think. So, we can say this is the the 13:53 rock here. It's in inertia of rest, right? It's it is in rest and it has 14:00 inertia. It's lazy to move. And similarly, you can see this big panda, right? He's sleeping there, right? He's 14:06 having a nice afternoon nap. So we can say the panda is in inertia because you 14:13 know you need some force to wake him up right or to make him moving right. So normally we talk uh about things uh 14:20 non-living things like rock but I just wanted to put this picture also of the panda the lazy panda reminding you of 14:27 inertia right excellent guys. So please remember the property by which it 14:32 resists its change of rest or motion. So that's why we can talk about two types Types of Inertia 14:38 of inertia. Right? So we can divide inertia into two types. We can say there's inertia of rest and inertia of 14:47 motion. Right guys? Okay. So this rock you can see the rock is in inertia of 14:54 rest. So this example is why because it's already at rest right. So the rock 15:00 is already at rest. So it's lazy to move. Right? We need to apply a force to 15:06 move it. So body which is already at rest is under the category of inertia of 15:13 rest right. All bodies they have an inertia right. Similarly this bike is in 15:19 motion right. So can you see this uh in this race right? This biker is in motion 15:26 here guys. Can you see this bike is in or let me use the yellow color here 15:31 right? I think it'll be more visible here. So this bike is in motion and so 15:38 this is called inertia of motion. Why? Because it's already in motion. He didn't start the bike. He's already in 15:44 the race. The bike is already moving. So we can say this is inertia of motion, 15:49 right? Okay. And to stop the bike, you need to apply a force or basically you need to press the brakes, right? The 15:55 biker needs to press the brakes, right? Then the bike will uh stop or you know the friction of the road, right? So it's 16:02 in the inertia of motion. So please remember our inertia can be divided into these two categories. Inertia of rest 16:09 and inertia of motion. Excellent guys. 16:15 So now I have some really interesting examples for you. So I want all of you to try. So I have this question here for 16:21 you guys. Uh I'm going to play this video here and you need to tell me if it 16:26 is inertia of rest or inertia of motion. Right? So again let me just summarize what we did. There are two types of 16:32 inertia. Inertia of rest and inertia of motion. Uh I know some of you guys are 16:38 experiencing buffering guys. Uh but uh my internet speed is pretty good. Maybe it's due to the server or something, 16:44 right? So just be patient. Uh usually the buffering gets fixed in 30 seconds or a minute, right? So uh sorry about 16:51 that guys if you're experiencing it, but I did check my net speed. It's really fast today. So it's uh might be just due 16:58 to a server issue. So please be patient and let's go ahead and try uh this thing. So I'm going to show you some 17:04 very interesting examples and you need to tell me if it's at inertia of rest or inertia of motion. Okay. So let's let me 17:11 go ahead and show you this video. All right guys, so I'm going to play this video for you and you guys watch and 17:17 tell me what type of inertia inertia of rest or inertia of motion. Okay. So 17:23 let's try this. 17:29 Now, if the person driving suddenly has to apply the brakes, 17:34 did you see what happened? I was thrown forward. If I wasn't wearing my seat 17:40 belt, I would have hit the front seat in front of me. Or if I was driving, I 17:45 would have hit the windscreen. So, which law of motion applies to this situation? 17:50 What do you think? 17:57 All right, guys. Hope you watched that video, right? So, as you saw, I was in the car, right? Okay. And then you need 18:04 to tell me, so I was in the car and brakes were suddenly applied. So, what was I in inertia of rest or inertia of 18:12 motion? So, come on. I want all of you to try. 18:18 So, come on guys, go ahead and try this. 18:25 So, I want everybody to try here. Okay. So, what do you think, guys? My 18:31 net speed is uh good. I did uh take a look, but sometimes, you know, there's a server issue or something. So, just be 18:37 patient and you'll soon find the buffering just uh get set in a couple of 18:42 minutes. Right? I have checked my uh net connection and it's pretty fast here. Right? So, very 18:49 good. Uh Sh I think is uh okay, good. Some of you are able to watch it more clearly. Uh so uh in case you found some 18:56 buffering issues. So what happened? You know I was in the moving car and the brakes were suddenly applied. Okay. And 19:02 then uh you know what happens? Let's say you're in a moving car or a moving uh bus and the brakes are applied. You tend 19:09 to fall forwards. Right guys? So the question is what type of inertia are you 19:14 in? In inertia of rest or inertia of motion. So guys think again. You're in a moving car and suddenly the brakes are 19:22 applied, right? So let's say you're sitting in a moving car, you tend to fall forwards like this, right? You know 19:27 that when the brakes are applied, you tend to fall forwards. So what is it? What do you think guys? Inertia of rest 19:33 or inertia of motion. Excellent guys. Excellent. Superb. So 19:39 here the answer is inertia of motion. And let me explain it to you. Right? Uh 19:45 so in case you didn't get to watch that video clearly due to the buffering problem. So basically when you're in a 19:50 moving car right the car is moving and since you're sitting in the car you are 19:56 also in motion right you may think you're sitting in the car you're at rest right but if an observer outside sees 20:02 you you're moving along with the car right so you're in inertia of motion and suddenly if the driver applies the 20:09 brakes right we tend to fall forwards you know that right like this right? So you're in a moving car and suddenly the 20:15 brakes are applied. You tend to fall forward. Why? Because you are in the 20:20 inertia of motion. And remember inertia is laziness of the body. Your body, right? In this case it was me. I want to 20:27 continue to be in motion. Right? So I want to continue to be in motion but the 20:33 brakes have been applied. So the car comes to a stop but our upper part or 20:38 the upper part of our body continues to move and that's why we move forward. 20:43 Right? So is this clear to everyone? Because you're sitting in a moving car. Think about yourself. You are in motion. 20:50 So you are in the inertia of motion. And when the brakes are applied, suddenly 20:55 your body want to wants to continue to be in motion. Right? So that's why when the brakes are applied, the car stops, 21:01 but you tend to move forward. Okay? And that's why you are in inertia of motion. 21:07 Excellent guys. I'm going to show you some more interesting examples and I hope you can watch the next video clearly. Otherwise guys, do go back and 21:14 watch the replay of the video. That will certainly be clear. So, sorry about it. There's a buffering problem, but I did 21:20 check. My net is pretty fast, but you know, we have these server issues sometimes. So, no worries. Let's take a Magic Trick 21:26 look at our next video. Okay. So, I'm going to uh mute myself and you'll be 21:31 watching the video uh the audio from the video. Okay guys, so let's take a look here. 21:39 And again guys, you need to tell me what type of inertia, inertia of rest or inertia of motion. So let's take a look. 21:51 You might have seen this magic trick before where they pull the tablecloth and the things don't fall. Now I'm not a 21:58 magician, so please wish me luck. Let's try. Ready? 1 2 3. 22:08 Wo! I'm happy it worked. Now, let's take a look at the action replay and see 22:14 which Newton's law is behind this magic trick. As you saw there, when I pulled the 22:21 tablecloth really quickly, these things hardly moved or didn't fall. So, how do 22:28 you explain that? 22:34 Excellent guys, you guys are awesome. I already saw a lot of answers out there. So, hope you could watch this video 22:40 better, right? So, very good. Uh, let's discuss the answer. So, in this video, 22:46 as you saw, you've seen this magic trick and you should try it yourself. You know, I was actually pretty scared I'll 22:51 drop all those things on the table, but you know, luckily it worked the first time. So when I pulled that tablecloth, 22:57 right, you saw that those things did not fall, right? So did you see that guys? 23:02 These objects here, right? So these objects uh on the table, right? Uh which 23:09 were placed on the cloth, these objects did not fall. And what was the initial 23:14 condition of these objects? These objects are at rest. Right? Excellent. 23:20 Awesome. Everybody's uh great answer. So the objects are at rest here, right? And 23:26 when I suddenly pull the tablecloth, right? So uh these objects are lazy. 23:32 They want to continue to be at rest. They don't want to move with the tablecloth. They're lazy, right? So they 23:38 stay in the inertia of rest is the answer. And that's how this magic trick 23:43 works. Right? So these objects uh so that's what the magician does, right? He pulls the tablecloth really fast, right? 23:50 They're more expert than me. you know I just tried with these few objects and they tried it with many things so they 23:56 pull the tablecloth and the objects continue to remain at rest and so they don't fall okay because of their 24:02 laziness and the slippery moving tablecloth just moves along okay so that's what so the answer of this 24:09 question is they're in the inertia of rest. Awesome guys and guys if you're enjoying this video please hit 24:15 [clears throat] the like button. Sorry about if there's a buffering issue, guys. You can watch the replay or just 24:20 stay on. The buffering issue usually gets solved in a couple of minutes. All right, guys. I have another interesting 24:26 example for you and again the same question because we're talking about the concept of inertia. So, you need to tell 24:31 me guys again after watching this video. So, I'll mute myself and you need to tell me uh is it inertia of rest or 24:39 motion? Right? What is the case involved here? And we'll analyze it. Okay guys, so I'm going to go ahead and play this 24:45 video. Please take a look. 24:52 Or if I leave the rope, in which direction will the ball go? So, let's go 24:57 ahead and try it out. I'm going to leave the rope and you carefully look which 25:03 direction the ball is going to go. Are you ready? 1 2 3. Now, let's take a look 25:12 at the slow motion replay. In the slow motion replay, can you see 25:17 that the ball goes off in a straight line when I leave the rope? 25:26 All right guys, so a lot of you saw that. Very interesting. I see Kumaran has an interesting he's telling about 25:32 inertia of direction. Yes, that's also another property we can talk about. And yeah guys actually uh somebody was 25:38 saying uh that I think Kir Gosh is it due to the cyclone? Yes we had this huge cyclone in Kolkata and actually I'm uh 25:46 very fortunate to be having electricity and internet available. You know lot of houses still in the city they don't have 25:52 electricity internet and water. So there's a because lot of trees have fallen there have been lot of power 25:58 cuts. So guys, the slow buffering speed could be due to the cyclone issue because the internet has been affected 26:04 in Kolkata, right? Uh so guys uh please be patient and thanks for sticking in 26:09 and guys do hit the like button. So uh what is this type of inertia? You saw 26:14 that I was swinging that ball, right? So the ball was moving in a circular motion and when I leave the ball, right? So I 26:21 left it roughly at this point. Okay. So guys, as you saw, the ball is moving in 26:26 a circle, right? So guys, you saw the ball was moving in a circle, right? And uh I 26:34 released it roughly when the ball was here. So let me just draw that. So I released the ball roughly when it was at 26:40 this point, right? Okay. So I released the ball there. And where did the ball 26:45 fly? Okay, guys. So where did the ball fly? Thanks guys for being patient uh 26:51 with the net issue, right? So where did the ball fly guys? You can see it flew 26:56 straight. Okay. So what is the type of inertia here? Okay. So this was our ball 27:02 and when I left it, it flew off like this. So clearly the ball is in motion, right? So it is definitely the inertia 27:10 of motion, right? And somebody had mentioned uh that this 27:16 is inertia of direction also, right? Because uh what you have here. So we can 27:21 say another another way inertia of motion or inertia of direction which falls under motion right because the 27:28 ball wants to continue moving in its direction and at this point you know the 27:34 tangential velocity is along this line right because the ball is wanting to 27:39 move in that straight line here when the ball comes somewhere here you know the 27:45 velocity of the ball is along the tangent to the circle right you might have read that in uniform circular 27:50 motion Right? So the ball is moving along the tangent and this is called the inertia of direction 27:57 or inertia of motion. It's a subset of motion because the ball wants to continue. It's lazy. It wants to 28:02 continue moving in its direction and that's how it goes straight. Right? Okay. So guys, this is also a very good 28:09 example of inertia of motion or inertia of direction. Okay. Excellent guys. 28:15 Superb. All right. Let's uh continue the topic of inertia and let's discuss it with mass. So how is inertia and mass Inertia of Mass 28:22 related? Let's talk about that. So I have some pictures here. So can you tell me is it easy easier to push a 28:29 stationary shopping cart? So can you see in this picture we have a shopping cart which is full of stuff. Right. So we 28:37 have this shopping cart and we have let's say this stationary train. Okay. 28:44 And we have a stationary train here. So both the objects are stationary. So can 28:50 you tell me which one is easier to push? So can you suppose you're pushing it, right? So which one is easy to push? So 28:57 let's say you apply a force here, right? So we apply a force here 29:04 on the cart and similarly we apply a force on the train. 29:09 So which one do you think will be easier to push or pull whichever way you look at it, right? 29:16 So let's say you're pulling the train from here. Okay, obviously right the shopping cart 29:22 is easier to push or pull, right? So it's easier to do that. Why? Because it 29:28 is lighter, right? We know from our experience, you can easily push a shopping cart, but you can't push a 29:34 stationary train. Okay, guys, make sense? So can you tell me which one has greater inertia of rest? The shopping 29:41 cart or the train? So that's my question guys. So tell me which one has the greater inertia of rest? 29:51 So which body has greater inertia of rest? And why do we say inertia of rest? Because it's already stationary. 29:58 So which one has greater inertia of rest? Come on guys. Okay. So very good. The greater inertia, 30:06 right? the greater inertia. Which body is lazier here? It's the train because 30:11 it is harder to push the train. Excellent guys. So, the answer is going to be train. The train has greater 30:19 inertia of rest. Okay? It's easy to push the cart. It's harder to push the train. 30:24 So, we can say the train is more lazy. It is more difficult to push the train. It has greater inertia of rest. 30:30 Excellent guys. Excellent. Superb. Right. Okay. So it has greater inertia of rest 30:39 the train. Now let's take a look. Let's say both the cart and the train were already moving. So let's say you had 30:44 pushed the cart and this cart was already moving here. So let me draw this 30:49 arrow here and let's say the cart was already moving. Similarly let's say this train is already moving. Okay. So we 30:58 have a moving train and a moving cart. Now the question says which one is 31:04 easier to stop? Is it easier to stop a shopping moving shopping cart or a moving train? Okay, so guys, can you 31:11 try? I know some of you are saying inertia of the internet. So, you know, guys, uh again, it might be due to this 31:17 cyclone effect. So, sorry about that. Uh thanks for sticking in, you know, and guys, you can watch the replay on the 31:23 parts that buffered. So, come on guys, can you tell me is it easier to stop a moving shopping cart or a moving train? 31:30 What do you guys think? So, come on. Okay, which one is easier to stop? 31:36 Right, the cart or the train? Excellent, guys. Right, it's easier to stop the So, easier to stop the shopping cart, 31:46 right? Because you know if the shopping cart is moving, you can easily put your hand and stop it. But you don't want to 31:52 be standing in front of a moving train, right? Because a moving train is huge. It has lot of inertia, right? Excellent. 32:00 So, shopping cart is easier to solve. Stop. Right. So now if I ask you which one has greater inertia of motion 32:07 because these guys are moving. So which one has greater inertia of motion guys? 32:12 So come on. I want all of you to try. So who has greater inertia of motion? The 32:18 cart or the train guys? Think carefully this time. So tell me is it going to be the cart here? The moving cart I mean. 32:25 So which one has greater inertia of motion? The moving cart or the moving train? 32:32 think and answer this question. Excellent guys. I see Adira, Rashmi, right? Cavia, very good guys. Shinas, 32:40 Muri, excellent. All of you have the right answer. The greater inertia of mo 32:46 motion is the train again. Right? So guys, take a look here. So we said which 32:54 one had greater inertia of rest? The train. The train is more massive. So it's easier to push a stationary card 33:01 but more difficult to push a train even though both are on wheels. Okay. So train had greater inertia of rest if 33:08 it's stationary. Similarly the train also has greater inertia of motion. It is more difficult to stop a 33:15 moving train than it is to stop a moving cart. Excellent guys. Superb. So now can 33:21 you what can you conclude guys? What is the relation? So can you guys tell me what is the relation between mass and 33:29 inertia? Right? So if you compare this cart and train, can you tell me are mass 33:34 and inertia directly proportional or inversely proportional? Come on, I want all of you to try and please write it in 33:41 the chat. I'm taking a look. Which option do you think? So is inertia directly proportional to mass or is it 33:47 inversely proportional? Okay, excellent guys. Excellent. We can say super right 33:53 answer. We can say that inertia 33:58 is directly proportional to the mass. Right? What is the meaning of directly 34:04 proportional? If mass increases, inertia increases because we saw that the train, 34:09 right? The train has bigger mass, larger mass. 34:15 So train has larger mass, the cart has smaller mass, right? the mass of small mass and the 34:24 train has a large mass, right? Okay. And so we saw that clearly that inertia of 34:30 the cart is small, right? Because small mass, small inertia and inertia of the 34:36 train whether you take inertia of motion or inertia of rest with those examples I show you both both cases, right? I 34:42 showed you. So inertia is also going to be large in this case, right guys? So 34:48 larger mass larger inertia that's why directly proportional directly proportional means if mass increases 34:54 inertia will increase. So if this guy increases inertia also increases. Similarly mass decreases inertia 35:01 decreases. Okay great. Excellent. And that's why guys we can say mass is a 35:07 measure of the inertia of a body. Very important point in physics. We can say that mass here right? So mass is a 35:14 measure of inertia right? So in fact it is the mass of a 35:20 body that is measuring the inertia. So a body which has larger mass like the train has larger inertia. A body which 35:26 has less mass like the cart has lesser inertia. Let me write this large down here. Right? Okay. So all of you can see 35:34 it. The inertia will be larger for the train. Right? So uh mass is a measure of 35:41 the inertia as I've written here. Can you guys see mass is a measure of the inertia of a body. Clear guys? Awesome. Units of Mass 35:50 And guys, can you tell me uh this uh very important to know the units? What is the unit of mass? So, can you tell me 35:56 what is the SI unit of mass guys? So, come on. So, who can tell me here the first 36:02 question here guys? What is the SI unit of mass? And this is our second question. What is the CGS unit of mass? 36:09 Okay. Very important to know your units. Okay, excellent guys. Excellent. So the 36:15 SI unit of mass is kilogram. Superb, right? And it's denoted by kg. 36:23 So please remember that it's not gram. The SI unit of mass is kilogram. Right? So if you measure a bag of potatoes in 36:31 SI unit, we will say let's say it's the potatoes have a mass of. So mass is 36:36 let's say 5 kilogram kg. This is we are using the SI unit here. And guys, can 36:43 you tell me what is the CGS unit of mass? Come on, I want all of you to be super clear about your units and be 36:48 clear about their conversions. Okay, very good. Very good, guys. So, don't confuse this. The CGS unit. So, SI unit 36:56 is kilogram and cgs unit is gram. And it's usually denoted just by small G. 37:02 You don't have to write GM. Small G is enough. Okay, grams. So if you measured the mass of the potatoes right so let me 37:10 write this in pink color when we measured the mass in SI units of the bag of potatoes it was 5 kg and if you 37:17 measure it in convert it to SI CGS units so that was in SI if you convert it to 37:22 CGS units it's going to be 5,000 g because you know that 1 kg is kilog kilo 37:30 means th00and right 1 kg is a,000 g simple everybody knows this So mass is a 37:37 measure of the inertia and its unit is kilograms for SI unit and gram for CGS. 37:43 Excellent guys. Can you tell me what instrument is used to measure the mass? I want all of you to try. And guys, if Measurement of Mass 37:49 you haven't hit the like button, please hit it right now and do share it with your friends. So thanks guys. I want all 37:56 of you to hit the like button. Hope you're enjoying this session. And uh what is the full form of CGS? AJ is 38:02 asking centime g seconds. Okay, so that's a good question. So easy way to 38:07 remember CGS means cm g seconds and that's why the unit used here was grams, 38:14 right? It was grams because cgs stands for cm g second. Clear guys? So can you 38:21 tell me what instrument is used to measure the mass? Is it a beam balance or a spring balance? So come on, I want 38:28 all of you to try. Okay, excellent guys. So beam balance is the correct answer. 38:34 Beam balance is used to measure mass, right? You've seen what a beam balance looks like, right? Where you put the 38:40 object here and you put the weights on the other side. And let's say, so these 38:45 are your weights, right? And this is what you're measuring. Let's say you're measuring an apple, right? The mass of 38:51 an apple. So you put the object over here. Okay? Uh I don't think I'm very 38:56 great at drawing, but I'm just trying to show you, right? So that's a beam balance. And guys, what is used for a 39:01 spring balance? A spring balance is used to measure weight of a body. The force with which earth's pulls gravity. And 39:08 guys uh the sorry the earth pulls an object. And guys you know the mass the unit is kilogram and weight the unit is 39:16 SI unit is Newton right after Sir Isaac Newton. Okay. So beam balance guys 39:22 remember is used to measure mass. That's the correct answer here. Okay. 39:28 Excellent. Okay. Great. And I have this uh question for you, right? So here's Homework 39:34 your homework question. If you're standing in a stationary bus, right? So look at the question. If you're standing 39:39 in a stationary bus, we tend to fall backwards when the bus starts. So imagine you're standing in a stationary 39:45 bus, right? Uh and when the bus starts, we tend to fall backwards, right? So if 39:52 you're standing in a stationary bus, when the bus starts, we tend to fall backwards, right? So what is it due to? 40:00 Is it due to inertia of rest, inertia of motion, due to velocity or friction? And 40:06 I want you to write your answer in the comments below. Okay, so I want everybody to try. I'm not going to give 40:12 away the correct answer here. So guys, and I see a lot of you write the answer immediately after this live class. It's 40:18 great to see that. So I promise to reply to your answers as soon as possible. So please try this homework question when 40:24 you're standing in a stationary bus. So think about it. You know Newton's laws of motion is you can see it all around 40:30 you. So always you can think and observe. So when you're in a bus or in a vehicle, right? And if you're standing 40:37 when the bus starts, so it was originally stationary, you tend to fall backwards. Okay? And why is this? Is it 40:44 due to inertia of rest, inertia of motion, velocity or friction? I want all of you to try and guys do hit the like 40:51 button. Sorry about the buffering issue. I think it was the after effect. 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