Mission Physics 3.0 | LAWS OF MOTION (Lecture 03) | From Basic to Advance | 180/180 in NEET & JEE

[00:00:04]So hello children, all the sounds are coming well, so every child who is here is coming in his presence in the comment box, Walekum Salam son Walekum Salam Walekum Salam, so hello dear children. So son, how are you all? Hope you all are fine and doing well.

[00:00:58]Come on sons, as you all know, our second chapter of Mission Physics 3.0, our second unit is going on, which is named Laws of Motion. Two videos have appeared on this.

[00:01:10]Video number one and video number two. Ok? What happened yesterday was video number two. In that I discussed about Newton's second law and showed how force calculations are done on various cases.

[00:01:26]Okay kids, okay kids, here every day our other kids too, to whom this course reaches, are also getting added, come on kids, let's start today's session. Come on dear children, PDF notes are uploaded on the Telegram channel only after the video.

[00:01:54]You can click on this. You can be added to the Telegram channel. You can download the notes from there.

[00:02:01]After the Telegram channel, here is our WhatsApp group. It is an open group. Doubts, other things, books, whatever you need, you will get it here.

[00:02:15]Change in velocity change in then if you want to find the change in velocity then m will not come in it 2v cos theta will come but m will not come, m means momentum when you multiply the velocity change by m you will get change in momentum so if you want to find the [nasal sound] change in velocity then m has to be subtracted from yesterday's formula.

[00:02:39]Come on dear children, let's start today's session.

[00:02:45]Number one again dear children once again which cases I showed you yesterday.

[00:02:49]Come on kids, I showed you number one.

[00:02:52]Still, I will remind you a little bit once.

[00:02:54]Ball dropped from height. Number one I taught you was ball dropped from a height.

[00:03:07]Ball drop from height. The ball was dropped from a height.

[00:03:10]Ok? I explained this yesterday.

[00:03:12]So if you want to see the diagram also to remember a little.

[00:03:18]You dropped your hair from height cute kids h1 hair went down. Takkar's hair went back.

[00:03:26]This way the height h2 moved back. Correct? So dear children, what formula did the force come up with in this case?

[00:03:35][nasal sound] The force came from the Delta. After that came dear children, in brackets 2g1 + 2g2, this was the formula of force dear children.

[00:03:50]If you want to find the impulse, then multiply delta t and then only m and this term will come in it. Delta t will not come. Ok? This is it. Well, what other case of this will come, dear children? The ball rebounded and fell from H. Climbed back from H itself.

[00:04:10]So the second part of it which came, dear children, was H1 = H2. Son, I am making you revise yesterday's formulas a little bit.

[00:04:21]Ok? Okay sir. What formula of force came at that time? At that time the formula of Time Force came. In this, h1 and h2 have to be equated. Nothing else.

[00:04:31]2m/ Delta t is what we get. Then came the equivalent of 2g under the root. Here is the formula dear children.

[00:04:41]And you saw the third case also. In the third case, when the hair fell, it did not grow back. That means h2 in the third part which is equal to zero dear children. When h2 0 came, what was the formula of force? Say m/delt 2g or h1 because it came up only once.

[00:05:04]So these are the things you learned yesterday.

[00:05:08]Write it again so that you can revise it. You will write it at the end. Don't write now. Do n't write now, son. Correct? I am revising all the formulas once again at last.

[00:05:18]Ok? So that's how it came about. Here it comes, dear children.

[00:05:31]Ok? Is this clear till here, dear children?

[00:05:35]If it is clear then show your presence in the comment box also, children.

[00:05:43]Correct. After that, children, you saw the second case.

[00:05:47]Yes sir, we also saw another case in which there is a ball striking wall. Ball striking wall Ball striking wall Okay kids, look dear kids, have you learnt its A part, have you learnt this, this is a wall, this wall, the hair came like this dear kids and came back, okay dear kids, let's come back dear kids, the hair velocity went from V and came back from V only.

[00:06:27]Collision I considered elastic. In this case, Force's formula, dear children, twice MV/ T, this was formula number one. Okay, dear children, what was the second part of this?

[00:06:41]The hair went on strike and did not return. So what will happen in that case? The hair went away but did not come back after being reflected. The hair passed through the absorbing surface but did not reflect back.

[00:06:55]You saw this too. The force had come out.

[00:06:58]It has empty mv/t. Ok? He had come.

[00:07:05]You saw these two things. Good. If now it will go from u and come from v. Then the initial momentum is different, the final momentum is different. I have to take out change for two. Went here from V only, came back from V only.

[00:07:17]Yes. Went from V and did not return. If U goes from V1 and comes back from V2 then this formula will not work. It will go with one velocity and come with another velocity. So what to do in that case? The initial momentum has to be calculated separately. mv1 Final momentum - MV2 Then subtract both and get the answer. Alright dear children? here comes.

[00:07:40][nasal sound] And you saw the third case of this. This ball tried it at an angle. This ball struck at an angle. The ball strikes at an angle. When the ball strikes, it reflects at an angle theta and comes back to the dear children. It came back after being reflected. So what happened dear children? Force is perpendicular to all this time. Twice mv cos [nasal sound] theta by t this is it children twice mv cosθ/t okay and the force parallel to the wall which is dear children is equal to zero and its fourth part D part let me write the D part here also you saw hair i hair i hair i but it is not reflected so in this case both the forces are force parallel to wall parallel to wall okay mv sin theta / t force [nasal sound] perpendicular to wall mv cos theta / t and the net force which will come out is the resultant of these two will come out to be equal to mv b / d so these are the things dear children what we have learnt this is it dear children oy hoye hoye hoye note it down and show your presence in the comment section also children.

[00:10:12]Yes dear children, I taught you exactly these things yesterday and we also asked a lot of questions on these, children, we also asked a lot of questions, come on children, let's move ahead, now today will be case three. Case number three is what I will teach today. Case Three Floating Plate or Floating Disc Say floating plate or disc.

[00:10:49]Come on kids, here it is.

[00:11:03]Ok.

[00:11:07]Now keep an eye out, dear children. If we move the hair on the disk, there will be two cases. The hair will be reflected and will come back or the hair will not be reflected and will come back. Correct?

[00:11:21]But we will place the disc or plate like this.

[00:11:24]This is how we placed it vertically. This time the wall was like this. Now we placed it horizontally.

[00:11:30]Horizontally like this. In the first case, the wall was vertical. In this way the hair went away and came back.

[00:11:36]Correct? Or like this, if it went at an angle, it came back at an angle. These were two things. Now this time I hung it in the air like this. It is placed horizontally like this. But kept it above.

[00:11:47]We will run it from below. Will run the hair. Dear children, we ran it like this.

[00:11:55]Correct?

[00:11:56]But if you have to bowl not just one ball but many balls or bowl many times, then what should happen? This should not fall.

[00:12:04]This should not fall. You have to discuss the equilibrium condition. Okay baby guys?

[00:12:10]So is the disc. The mass of the disc is capital m and the mass of the hair is small m. The hair went, collided, and came back. The hair collided with velocity you, it got reflected with velocity and came back very good kids, very good kids, so what do we have to do, we should not let it fall, it has fallen, okay sir, at the time of falling, it means it floats, it is in equilibrium, bullets are continuously coming from below, bullets have to be stopped continuously, it will fire at the centre of mass, bullets should not be fired on the sideways, son, then the effect of torque will also have to be taken into account, for now I have skipped that part. Okay sir, which part did you include? I hit all these balls on the center of mass. Come on dear children, let's see the center of mass. This is the center of mass I have created. What did you make of the children?

[00:13:05]Tell me son, what are the forces on this center? Okay sir. Sir, its own force from below will be mg. So what is mg dear children? It is wet. Whose weight is it?

[00:13:19]Weight of the disc. The act is happening from below. Sir, the balls we bowled, Sir, the balls we bowled, applied force upwards. I will write Force Due to Balls in FB. Now sir in equilibrium condition upward equal to downward. Sir, dear children, the force of the balls is equal to mg.

[00:13:45]Okay sir, I understand sir. Ballas forced it upwards. Both of these are equal in weight from below, sir. Now there are two conditions in ball force.

[00:13:55]Sir, what is it? If the ball reflects back. Well done. The ball reflected and came back. Sir the force will come twice mu /t sir. This is the force of one ball. Sir, I did not bowl a single ball. We threw n balls, so multiply this by n dear children.

[00:14:21]This is the force of n balls. Sir, if the ball is absorbed, that is, if it does not come back after being reflected, then I am using the effect of the mass of the balls negatively.

[00:14:36]Now he is not adding mass to it.

[00:14:38]That will become a more advanced level.

[00:14:41]So you will get sir mu/t the force of one ball of n balls will be multiplied by n sir this means sir this means sir we have to do one thing case number one we have to discuss here separately when ball reflects back or balls reflect back ok when balls reflect back when balls reflect back ok sir balance this force with mg sir twice mu/t and multiply n this [nasal sound] will be equal to mg dear children so ok whatever we need we will get it sometimes n will be needed sometimes n/t will be needed sometimes u will be needed whatever we need we can get ok sir this means second when balls do not reflect back when balls do not reflect back. Okay sir, if the balls are not reflected then we will use mu/t multiplied by n sir, that will come equal to mg.

[00:15:59]Here comes your answer dear children. I completely understood your answer sir. Whatever is required, cross multiply it and say u, n, now I will also show you the questions children and if it goes at an angle, crutch crutch will go at an angle after reflection, then twice mu cos theta will be balanced with the component mg, here it will come twice mu cos theta, then you can equate that equal to n / g and mg, dear children, you can equate it, did you understand this much? If you understand, please write your comments in the comment box. we will proceed.

[00:16:43]I will show questions on this, children.

[00:16:57]And please like it too. Please put likes also. Please put likes also.

[00:17:08]Okay child, you show your presence in the comment box also, then I will show questions on this. Did you understand the concept?

[00:17:15]First you will calculate the force on the ball in the same way as you calculated the force on the wall and multiply it by n because it has to balance the weight of n balls. Nothing else.

[00:17:36]Come on kids, move ahead. Here is your question. It is asked in many competitive entrance examinations. So what's in it? Okay, a disc of mass, so I will make it a little smaller in size. It has become much bigger. There should also be space to solve on the side.

[00:18:01]Come on kids, it's okay now. Come on kids, what is the question? A disc of mass 100 grams. Here is the dear children disc. Here is the dear children disc.

[00:18:18]What is the mass of the disc, children? 100 grams.

[00:18:23]Whose mass is floating horizontally by firing bullets, bullets were fired from below, bullets were fired from below, and the mass of the bullets will be small m, its mass will be capital m, yes its mass will be small m, which is equal to 5 grams with the same velocity at the same rate, so the velocity of every bullet is the same, let's say u and the same rate is 10 bullets per second. Yes. Well, 10 number of bullets per unit time is equal to 10, dear children. But second, he has said but second. Hence n/t. The Bullets rebound with the same speed. So it is coming back after being reflected, children. It is coming back after being reflected. You have to find the velocity. Come on dear children, try this question. I will see whether you will get this question or not. Come on son, I will also set a timer here.

[00:19:26]I want you to at least try this.

[00:19:28]I will set the timer. I will give it to you in 2 minutes and 10 seconds.

[00:19:44]Come on guys, give me the baby. Do it and give it to me. I will wait for your answer. Do it sons and give the answer.

[00:21:32]10 means 9.8, okay this is centimeter per second, son, take special care of it, you will get the answer in meters, come on brother, come on, come on, this is done. Well, you know we'll take out the Force Due to Bullets in advance. The force is due to the bullets as it is reflecting back.

[00:21:57]Twice mu/t is the force of a bullet, multiply this by n. So this is the force of n bullets.

[00:22:04]Alright dear children? Okay sir, force due to bullets will come. Two is two.

[00:22:10]What is m? Mass of bullet. The mass of the bullet is five. Children, you will write 5 * 10 power -3, what is you dear children, the velocity which you have to find divided by t, this is not t, n / t is given, what is the value of n / t, children 10, so you multiply it by 10, you see 5 to 10 10 100 * 10 power -3 10 power -1, so you will get 10 power -1 times you, this is four force because of the bullets or you can say you can also write by 10.

[00:22:48]This will run in meters per second. Well, this is the force due to bullets, equal to the weight. How much is his weight m*g force due to bullets dear kids? u/10 Well what is m cute kids? That's 100/1000, right? 100 / 1000 and put the value of g as 9.8 because he has given the answer in 9.8 only.

[00:23:12]Look, two zeros will go with 0, two with two. So the value of u you got is 9.8 but the unit you got, dear children, is meter per second and not centimeter per second.

[00:23:24]You will get seconds per meter, child. Correct?

[00:23:27]What do you have to do now? You have to convert it.

[00:23:29]Multiple 9.8 by 100. You will get 980 cm. per second. So 980 is your answer. So take special care of it. There is a difference in units.

[00:23:44]Dear children, the units in the given question are different. Correct? The unit in options is different. So this was a very easy question. Come on dear children, let's move ahead.

[00:23:54]Come on dear children, this question has come.

[00:23:56]Please do it and give it to me. Let me move this up a little and make it a little smaller so that there's space to solve. Come on dear children, try this question. Do it.

[00:24:08]I will wait for your answer. If there is a similar question, then I will set a timer for two minutes. Yes, now I will set a timer for two minutes only.

[00:24:38]Before this, I had given 10 seconds extra.

[00:24:45]Come on, come on children, give the answer. Give the answer.

[00:25:34]Son, please do it and keep commenting along with it.

[00:25:56]Hurry up son, hurry up son.

[00:25:58]Great, great, great.

[00:26:03]Great, great, great. Well done.

[00:26:09]Rest of the children who are online should also answer.

[00:26:28]Come on kids, I will cut it in the last 10 seconds. Okay son, okay. Solid disc of mass m. Here is a solid disc, dear children, and its mass, which is capital m, is equal to the number of stones thrown horizontally in the air per second. By throwing 40 stones per second, how many stones were thrown?

[00:26:50]The number of stones per unit time, dear children, is equal to 40 stones per second.

[00:26:55]To strike the disc in each hour, everyone struck the disc at what speed?

[00:27:02]Its speed is six meters per second. Ok? If the mass of each stone is 0.05 kg, the small mass of each stone is 0.05 kg. Correct? You have to remove the mass of the disk. Let go.

[00:27:26]So, here it is not even written whether it will come back after being reflected or not. This is not written.

[00:27:36]So you have to accept this, it is a common thing, friend, a common common life example, when you apply this, it will strike and come back, right, if you apply a stone to a plate, it is a solid disc, if you apply a stone to a solid, it will get absorbed and will reflect back, right, it is not an absorbing case or a reflecting case, come on dear children, first you will find out the force due to stones or balls, it will come out, sir, twice mu / t and sir multiply n, come on first find out this, it is a good method, force of balls twice, so what is m, what is the mass of the stone, mass of the stone is 0.05, what is u, dear children, what is the speed, speed six and n / t, number of bullets per time, that is equal to 40, okay dear children, so what will come out, if you see, dear children, force due to bullets, it will come out, it will come out, 0.1, this is 0.1 * 40, force 0.1 * 40 is 464, this is 24 Newton, okay, what do you have to equate this 24, it is equal to mg Just find 24 [nasal sound] = m and what is the value of g, dear children, the value of g is 10, okay now see, see. So dear children, according to us the mass is coming to 2.4 kg, but you see dear children, there is no such option. There is no such option but its half is there, its half is 1.2. So actually the answer should be 2.4 because when you throw the stone it will come back. It is agreed. But but but the purpose is the same. Our answer was 2.4, there is no such option here. This means we must explain ourselves. It is 2.4.

[00:29:36]Tick ​​it or you should have mentioned this: Does not reflect back or reflective.

[00:29:41]It should be mentioned. But according to me he has given the question incomplete.

[00:29:45]what shall we do now? If we consider it absorbing. This happened when I believed what?

[00:29:50]When I reflected, I accepted it. The mass came out to be 2.4. If it had not been two, then the answer would have come out to be 2.4. Well, if I consider absorbing, what do you mean, dear children? If we consider absorption then obviously the mass will come, half of that is 1.2 kg. You see, one of the two options is matching i.e. 1.2 kg. But this is happening only when we consider absorbing. And we did not accept it just like that. We solved for reflecting first. There should be reflecting. 2.4 came. There is no option.

[00:30:20]So I have considered 1.2, that is, it has done this absorbing. But according to me it should be mentioned in the question. Although it is not mentioned but it should be mentioned. Is it absorbing or reflecting?

[00:30:31]Well, here you understand that the option that came to us is a dream, that is, it has considered absorbing. Come on, dear children.

[00:30:39]Come on, come on, come on.

[00:30:43]Here you see this question has come in JEE Main.

[00:30:44]This is a JEE Main question. You see, this question is from JEE Main. It is written directly in it. This is a recent question of JEE Main.

[00:30:50]So I forgot to give an example in this.

[00:30:51]Which year's question is this? You see in this assume that marble strikes the disc and rebounds round word. This has been written.

[00:30:58]Try and answer these questions quickly. You are not both. And at that time we will consider it as reflecting son because it will actually be reflected. If both options are there then reflecting you believe that this will not happen normally. This will be a mention.

[00:31:20]You see, this is a recent question of JEE Main. There is a mention in this. Come on son, it's a disc. This is the disc.

[00:31:28]What is the mass of the disc? The mass of the disk is that capital m. Who is equal to this, dear children? Equal to 10 grams. Correct? Floating Year by Throwing Marbles. We placed marble pieces on it. Just how many marbles should I put? 10 marbles per second. That means n/ t is equal to 10 marbles per second from below if the mass of each marble is equal to 5 grams. Correct?

[00:31:55]Calculate the velocity. You have to find the velocity u.

[00:31:57]Good calculation assumes that the marble strikes the disc normally and rebounds. The word rebound is mentioned as child. The word ' remound' is mentioned, sir what will you do, will you find the force due to two balls, sir twice mu/t of one ball, sir multiply it by n, sir four is due to two balls, so two is what sir, what is m mass, mass of the ball is five, so you write it 5 * 10 power -3 sir [nasal sound] what is u speed sir, that is u, sir this is n/t number per second, sir that is equal to 10. Okay sir 5 2 10 10 100 * 10 ^ -3 that you know 10 ^ -1 so u / 10 we had already done this question so this has come for the second time sir u / 10 came [nasal voice] okay sir this u / 10 this force due to ball has to be made equal to the weight sir what is the minimum m mass of the disc which is equal to 10 / 1000 and sir keep in mind g this time we had kept it as 9.8 if you remember come on sir these two zeros these two zeros cancel this goes with it okay sir u you got 1 meter per second now see dear children this is what is coming, the Mosin which has joined late, watch this video first then it will come, it will not come like this. You have to first see its cases which I explained in the beginning, then it will come. So what are the speeds? So we get the answer u = 1 meter per second. Come on kids, this is the same question all the time. There is a similar question. So now there's a little data given in it. A little diagram and a graph are given. So children, please ask this question.

[00:34:04]I will reduce its size a bit so that it becomes easy for you to do this question, come on kids, I will reduce the time in it, yes I had given you two minutes, I will give you one and a half minutes in this question so that you can do it quickly, come on I have given you one and a half minutes, come on sons, do it in one and a half minutes quickly son and this time take special care of the unit of second on the meter.

[00:35:44]Let λ be the mass of the disk. This is the mass of discs, dear children. That is equal to 1 kg. Correct? Floating horizontally in air by firing bullets and the mass of the bullets is equal to 0.05 kg. Ok? etch vertically at the rate of 10 per second. That means n/t, dear children, is equal to 10. Good if the Bullets rebound. Look, it is written in this question, it is written rebound, come on dear children, first you will find the force due to the balls, twice mu * n / t, yes twice mu / t * n, come on son, the force due to the balls will come, twice m of the ball is 0.05, you have to find out n / t is equal to 10, so 10 will come to 0.1, see 0.1 * 10 becomes one, so fb you get is equal to one Newton, you have to equate this force due to the balls with the weight of the plate. So 1 newton m is 1 and g and 1 newton will be 1 u 1 u 1 u newton. Correct? The value of M and g is equal to 10. So you got 10 or 9.8 you can say 9.8 because I took g 10 that's why I got 10. If I had taken 9.8, it would have come out to be 9.8.

[00:37:20][nasal sound] Come on kids, let's move on. That's it.

[00:37:25]Come on, this was floating basic.

[00:37:28]Now dear children, we will come to case number four.

[00:37:31]On case number four.

[00:37:35]Hum Flowing Water Jet. Flowing water jet water jet, son, this is the fourth case, then I will show questions on this also, if everyone understood till here then come on sons, do one thing, first tell in the comment box whether you understood this much or not, if you understood well then comment plus like, then we will move ahead, come on children, see further son, see one thing, see one thing, if this is dear children, this is I have taken a pipe, I will explain it quickly, it is the cross sectional area, oh dear children and water is flowing with velocity v, okay, water is flowing with velocity v, it is so clear sir, it is absolutely so clear, I will tell you, dear children, please tell me how much is the mass flow, mass you will say sir, mass is equal to volume * density v, not velocity v, oh I will write volume, okay sir, sir, mass will equal volume * density, volume is area * length * density, okay, it is so clear, sir, this is area * length. Now I will tell you to calculate the unit time per mass. Sir, you will say about mass, Sir, area * length * row divided by time, t Sir, length / time is velocity or speed.

[00:40:13]So I will feel like crying. So this is the basic thing. So if I tell you how much mass is flowing? How much mass flow is taking place? Sir, you will say Sir Mass Flow, I will write it. How much mass flow is happening sir? You will say Ro L Ro L. If I say mass per unit time, see sir, it will come Ro A, then v will come Ro A.

[00:40:44]Okay, remember these things for now. Now, dear children, remember the same thing that when the object strikes, it reflects back from the velocity v.

[00:40:58]Force aapko aaya twice mv/t jab reflect ho ke nahi aaya. This comes at the time of reflection and absorption, dear children, mv / t and when it goes at an angle, when it goes at an angle, this same force will come, twice mv cos theta / t, remember and perpendicular force, it is okay to remember these three formulas, children, now see what we have to do in the flowing jet, hi hi, where did this come from, what have to be done in the flowing jet? You see dear children what to do?

[00:41:42]I placed this pipe against a wall.

[00:41:46]Dear children, in front of whom did you place the pipe? In front of the wall. So water came out from here and it struck it. Water came out.

[00:41:56]This one strikes it. Come on dear children, come on dear children, tell me case number 21. If if water reflects back if water reflects back if water reflects back if water reflects back okay if water reflects back what happened it reflected back yes sir water reflected back how much force did water apply on the wall sir twice mv/t okay sir m/t you taught us equal to rho sir force will come twice m/t it will be rho and along with it v sir force due to reflection will come twice rho² this rho I don't know how to write it properly I write it like e so take special care of that I never knew how to write it okay this rho became twice rho av² so this is when water reflects back here is the formula of force oy yes yes yes yes if water reflects back force will come sir twice rho sir the second part will come if water [nasal sound] does not reflect back if water does not reflect back and water strikes there and falls okay sir sir force due to Absorption will come sir, it comes empty mv by t sir m/t rho v its v multiple sir this will come rho a v square at the time of absorption its half sir force due to absorption will come rho this is not l rho, I told you I don't know how to write rho, very good sir did you understand this also, first note down this much children, then write comment in the comment box as well, whatever you read, what did you read, write this also because you must have read it once already. Those in class 11th must have studied in 11th.

[00:44:07]Those who appeared for NEET must have studied in 11th as well as in NEET batch. You are reading it for the third time. You see whether you are understanding these things well or not. I have two more things to teach you. It is okay in this, children, move ahead, sir, move ahead, now what is it, dear children, C part, okay, we will put a line in it, I will do one thing, I will arrange it, I will arrange it and put it on the side.

[00:45:26]Enough to explain. Will work. Such a big water root. What is the plan? We will arrange these and place them a little on the side.

[00:45:40]Everything should come. Let's go to the rest.

[00:45:48]Aye hi oh just that. Okay kids, okay, I will put a line here to separate it from there, I will put another line from here, okay, now kids, keep an eye on it, let's do it a little, it is now clear. Look dear children, in this part, if this water jet, this water root, tries at angle theta, then the force will get reflected and come back. Force of reflection twice mv cos theta by t m/t you know the force of multiple reflection from rho along with v sir twice rho² cos of theta good sir I understood this also water jat aap angle base strike kiya. He was striking normally. Okay sir fourth case B good if water strikes.

[00:47:19]Good with Speed ​​U good and Reflects with Speed ​​V good. Tried it from U to V.

[00:47:31]Sir Sir, at that time 2s mv does not come. 2mv occurs when the speed of going and coming is the same.

[00:47:38]Sir, you do one thing, the initial momentum of going will be equal to m * u, sir, the momentum of coming will be equal to -mu - mv - mv because the speed of going is u, the momentum mu of coming is mv minus because it is in the opposite direction, sir, change in momentum by time, if you minus both of these, sir -m will come out, v + u will come out, sir, change in momentum, sir, the force will come out, sir -m in brackets, v + u / t, this is the formula when the speed of going is u, the speed of coming is also with magnitude, I can take it in minus. Now there is the issue. Okay sir, you know m/t mass/time, right? Okay sir, Ro a u and not v because this is derived with speed u, when this is derived with speed u then Ro a u so the force you will get is dear children minus Ro, then in the bracket v + u a and you can skip the minus sign. So this is Force on Jat. If there is force on the wall, it will be a plus sign. I took this to explain.

[00:49:10]And one important thing is that in all the formulas, force is proportional to speed and speed is its square. Square of Speed.

[00:49:22]Square of speed Square of speed here also speed speed square of speed.

[00:49:26]So this means that if the speed of the water jet is doubled, then the result will be four times. So this objective type question has been asked in many exams.

[00:49:43]When the fireman held the pipe, the speed of the water coming out from there would double.

[00:49:50]How much will the force be? It will increase four times.

[00:49:52]Oh hi hi hi sir, you showed me some different things which got skipped in my mind and I could not remember them. Okay son, do it and ask questions.

[00:50:09]Come on dear children, the question is on this. A stream of water flowing horizontally with speed. A stream of water is coming out.

[00:50:18]Okay, okay, okay, okay, okay, at what speed is it coming out? It passed at a speed of 15 meters per second. Pushes out of tube its cross sectional area 10 power -2 meter square hits a vertical valve.

[00:50:34]It tried the wall. This is a question from NCERT text book. This is not an ordinary question. These are considered to be torn questions.

[00:50:40]Hits a wall near by.

[00:50:43]What is the force exerted on the wall by a water how much f assuming it does not rebound. When there is no rebound, the force of absorption becomes RO², this is called hard work, then whom do you call son to remember? Then how will you qualify the exam? This is the difference. Those who qualify the exam have to remember it. That is what is called hard work. If everyone remembered everything or if everyone remembered everything then everyone would have been selected which is not possible. Come on dear children, sir, please say something. Sir, why did you not give this density? Why should I give the density of water?

[00:51:28]Density of water is equal to 1000. Hey Baba, the density of water is equal to 1000. a area will come to 10 power -2 v is velocity that is 15 squared sir two zeros went with this two 15 squared 25 * 10 250 2250 Newton is your answer.

[00:51:58]Absolutely, absolutely, absolutely, absolutely, the more you practice questions, these formulas are automatically remembered, I have repeated it so many times here so that you remember it so many times, come on kids, move ahead, okay sir, this question has also come, let me move ahead, there is no need to solve it, you must know by heart, water jet, this is not a ball, this water jet, the water jet is coming like this, the water jet came like this, got reflected and went back and came at an angle theta, okay with the normal and rebounds elastically, what is the velocity of water is v, force exerted on walls, force ki, so the formula you get at the time of reflection is twice ro² cos theta twice ro² cos theta twice ro² cos theta twice ro² cos theta C option, similarly son, if instead of water there will be air, it will be air. There will be air. Same formula, density of air is different. This is the rest.

[00:53:28]Wind with velocity, wind is flowing, what is the speed of the wind, it will be 10 100 kilometers per hour, so to convert it into meters per second, what will you do, you will multiply 100 by 5/1, then it becomes meters per second, right?

[00:53:55]2 50 2 9 So velocity came to you 250 / 9 this came velocity against wall of an area just what is area equal to kids? 108 meter square force exerted on the wall by the air moving parallel to the wall after striking. He has said a good thing. It has not said whether to reflect or not. That is why it is said that when it tries to set the wall, what did it try to do with the wall, it goes parallel to the wall, it goes like this, this is how it goes parallel, this means it does not reflect back, it does not reflect back, just do this question, son, do it, do it, do it, do it.

[00:55:05]Come on son, please do it.

[00:55:16]Two will not come in this. Is it clear son? So it is not a case of reflection. The four that will come is Ro² four, dear children, the density of Ro is given by the year and is 1.2. A is the area, how much area is there, children? 108 and V is speed, that is 250/9 250 / 9 and by squaring this you will get the answer. So you can do this calculation, it is not a big issue.

[00:55:56]Come on kids, how many cases did you see? Earlier we saw Falling from Heights.

[00:56:03]Falling from Heights. This is what I saw. The second saw was the striking valve.

[00:56:12]Striking sound, the third one I saw was the floating disc, floating disc, three special cases and the fourth one what did you see, this flowing jet, flowing water jet, water jet, okay flowing water jet, now I will come to the fifth case, now I will come to the fifth case, case number five, case number five, children, towards case number five, okay, towards case number five, four, gun firing bullets, gun firing bullets, oy hoye, many questions have come on this, children, you might have read this for the first time, second time, third time, but you might have read it a little in jamb form. I brought all these cases to you in one place. So you found it a little easier this time. I do n't know how easy you found this thing. If you found it easy then please comment and like it first.

[00:57:30]Come on kids, first show your comments and likes.

[00:57:58]Come on kids, now let's see the song, son, I have made a song from the British era, Oye Hoye Ae, what song has it become? Well, at least my work will be done.

[00:58:08]This gun was initially at rest.

[00:58:12]Correct? What is the initial speed if it was at rest?

[00:58:15]Its equal to its zero. And it had bullets in it. There were bullets. Bullets Bullets were also at rest. Their initial speed is equal to zero. Correct?

[00:58:32]Come on kids. Correct. Initial speed equal to zero. Now this bullet that comes out of the gun has a backward recoil, you know that, I don't need it. The bullet came out with velocity also equal to the bullet and the mass of the bullet which is m. This bullet, please tell me about its change in momentum. Sir, the delta P of the bullet is equal to the final momentum mv, the initial momentum is zero, sir the change in momentum will be equal to m * v, sir it is the change in momentum, okay so the change in momentum for the bullet is mv, exactly this is the impulse, this is the impulse, but this is for one bullet, well done, what is it for one bullet, okay for m n bullets, capital n bullets, capital n bullets, if we are applying cube on n bullets, then what will be the change in momentum, dear children, equal to n times mv, this is dear children, change in momentum, if there are n bullets, change in momentum n times is mv, absolutely sir, absolutely good, now tell me the change in momentum has to be calculated as impulse, impulse is nv, okay, sir, if we have to calculate force. What to remove? Force.

[01:00:22]Well sir, force change in momentum divided by time. Well, what is change in momentum, dear children? NMV /t magnitude needed. You can remove the vector sign of v. So if you want to remove the force, dear children.

[01:00:39]Say the magnitude. nv / time. Who is this force on? Look son.

[01:00:45]Who is this force on? Completely. Who is this force on? This is Force on Bullets. Bullets Pe Force Hi Hi Bullets Pe Force Kitna Hai? nmv / t In this n is the number of bullets m is the mass of the bullet v is the velocity of the bullet t is the time. Well, the same force will be applied on the cube also. The action reaction pair will be equal.

[01:01:10]If force on cube is to be found. Its opposite force will also be applied on the cube. It will come -nmv / time t, the force on this will be the same on the gun, but if I tell you that I have to place my hand from here to the gun to fire the bullet, how much force will I apply on my hand to fire the bullet, how much force will be applied on my hand, it will also come to the same but its opposite sign force on the hand from here, if I have to apply force from here, if I have to find out the force on the hand, it will come to nv V / time, so these three forces are equal in magnitude, so the magnitude of all the three forces, the same amount of force on the bullet, the same amount on the gun, the same amount on the hand. It's just a matter of direction. If you understood this much then you already know what to do in the comments, kids. Do that.

[01:02:25]Let's move on. There is 90% chance of getting a question on this. There is a 90% chance of getting a question on this.

[01:02:35]Come on kids. Okay, what is this question on this? A machine gun is a machine gun. Fire is a bullet. It fired a bullet. The mass of the bullet is m and the speed of the bullet is v in meters per second. Well, the person holding the gun. The person holding the gun applied force f. I told you all three forces will be equal.

[01:02:58]What is the number of bullets?

[01:03:00]Seconds on the gun can hold. Number of bullets per second. Sir, what is the formula of force? nmv /t gives you n/t this is number of bullets per second so what will n/t be equal to? f/mv This is the number of bullets per second son f/ mv Okay. Go ahead. Go ahead. Do it. So, this is the CET exam of Hazrat Late Ji, a long time ago, although the exam is not conducted now, it used to be conducted a long time ago.

[01:03:52]Come on kids, what do you want to find out? Force exerted by bullet on gun.

[01:03:57]What is the formula of force, dear children? What is that? Well n bullets per second this time.

[01:04:04]This time the n is per second. That means n /t is the same as n this time. But he has said second, right? Soul n is not number of blades.

[01:04:12]It's number of blades.

[01:04:14]What would have happened according to our formula? nv / t This n / t is n this time.

[01:04:21]Yes. So the force you will get is n times mv, keep the time 1 second per second means time 1 second, what is the issue, n times mv, n times mv, move ahead, it is very important, see JE has come in JE Main many years ago, even after that it has been repeated in many exams, come on kids, do this question again, son, hurry up, hurry up, kids, what a machine gun fires is a bullet, what is the mass of the bullet, children, the mass of the bullet is 40 grams, okay, with what velocity, with what velocity, with a velocity of 1200 meters per second, the man can hold, how much force did the man apply to save himself, he applied 144 on his hand.

[01:06:38]How many bullets he can fire per second? Number of bullets per second? Absolutely simple formula. The formula for force is nv / t sir. The formula of force is 144 sir. n/t has to be removed. n/t has to be removed. Sir m is equal to 40 / 1000. Okay sir. Velocity is equal to 1200. Okay son, 2 0 2 0 with 0 0 with 48 so n/t you will get n/t you will get 144/48 how much will that be, this is coming 24 272 24 so three will come n/t 3 will come so n/t is fine. Yes, yes, absolutely n/t is 3 These questions have come many times. These questions are asked. Look son, in how many exams is this question like this in MCAT, in this a cube of mass. The mass of the cube is 10 kg.

[01:07:48]By the way, the mass of the cube is of no use here.

[01:07:50]This is used for conservation of momentum times recoil velocity. Let it go.

[01:07:54]Fire is four bullets per second. That means the value of n/t is equal to four.

[01:08:01]Mass of each bullet The mass of each bullet is equal to 20 grams. Well, the velocity of the bullet is equal to 300 meters per second. Force stopped to hold the gun. very handy. The formula of force is n / t mv The formula of force [nasal sound] is n / t 4 m is equal to 20 / 1000 and velocity is 300 how many 1 2 3 1 2 3 2 6 6 4 24 so your answer is 24 Newton.

[01:08:39]Let's move ahead. Similarly, see the same question in JEE 2023, that is, the question of 2023, just two or three years ago, come on kids, the average four is given, dear kids, how much is 125 Newton, what is the mass of machine gun fire, equal to 10 grams, kids, what is the speed, at 250 meters, you have to fire number of bullets, at second number of bullets per second, so the force you will get is nmv / t, ok the force will be 125 = n / t, just what is mv, 10 / 1000 * v, 250 will go in cross with 125 2 0, n / t will be equal to 50, here is your answer, here is the question of NEET 2004, again the mass of bullet is equal to 40 grams, velocity at 1200 meters, the force man can exert is 144 Newton, dear kids, n / t has to be applied. So you know n / t mv is equal to 144 = n / t m is 40 / 1000 * v is 1200 these two 3 these two 3 12 48 divide this by 48.

[01:10:28]So n / t will come to 144 / 48 which is equal to three.

[01:10:32]So n/t will give you three.

[01:10:35]This question has been repeated again. n / t = 3 We already did this.

[01:10:45]How many questions are these? How many questions are there?

[01:10:47]Man Thirs Bullets.

[01:10:51]Dear children, what is the mass of bullets? Please ask this question.

[01:10:53]But it has per minute.

[01:10:56]Take special care. But it is a minute.

[01:11:00]Come on, try this question. I will take this out on you in just a second. Take out n/t, you will get seconds, then I will show you how to convert it into minutes, yes of course you will multiply it by 60 because that much in 1 second, that much in 1 minute, multiple it by 60, come on son, first what is n/t mass, it is 50 grams, what is the speed, dear children, average force per second at 1000 meters.

[01:12:00]How much force is there, dear children? 200 Newtons. Correct? The maximum number of bullets per minute. You take out the n/t first.

[01:12:08]What is force equal to? n/t mv how much is the force dear children? 200 = n / t m is dear children equals 50 / 1000 well v how much is dear children? Equal to 1000.

[01:12:24][nasal sound] Three went with three. 50 would go with four.

[01:12:29]So the number of bullets per unit time you will get is four per second because you followed this system per second, it means four bullets were fired in 1 second, okay, what is 1 minute, 1 minute in 60 seconds, multiply four by 60, that is 240 dear children, here it is 240 [nasal sound] last case today's case number six, case number six, okay, if you understood what I have taught you till now, then comment in the comment box.

[01:13:28][sound of clearing throat] Particle in circle Particle moving in circle Moving in circular path I will show this case First you will comment in the comment box not one, not two, not all of them.

[01:13:58]Look son, what session did I conduct? How many questions, how many cases, six cases shown.

[01:14:03]Showed so many questions.

[01:14:05]Same for those who still don't comment after this. In this, he also goes a little advanced and asks questions, sometimes we do not need to go that much but I will keep teaching the basic concepts of the course, you know dear children mv2 - v1 / t, this is the force course, but still comments are not coming. This shame you have so many kids online.

[01:14:55]Come on kids, come on kids, this is v2 - v1. Jugaad Jugaad is another method but it may seem a little difficult to you. Easy Method v2 - v1 Dear children, what is this equal to? This is the difference in velocity. This is vector subtraction. The formula for vector subtraction is v1² + v2² - twice v1v2 equals cos theta. Hi hi hi hi I understood this too sir. Correct. Now if magnitude v1 and v2 both equal to v.

[01:15:38]Yes, the direction of v1 is different. Direction of V2 is different, direction of V1 is different, direction of V2 is different.

[01:15:43]But the magnitude of both is equal. As in uniform circular motion.

[01:15:47]So what will V2 - V1 equal? under root V² + V² - 2V² cos theta. Okay, 2v² 2v² in common bracket 1 - cos theta 1 - cos theta is equal to twice sine square theta / 2. Okay, sir, you will get 2v square, sir, this will be twice sin² θ / 2, sir, that will be 2 4 root of 4 2v² v sin theta by 2. Now dear children, understand this.

[01:16:35]If you want to find out the force in circular motion, sir we will do m / t. The value of v2 - v1, sir, is equal to twice v sin of θ / 2. Sir, after adding this, the force will be twice mv/ t sin of θ / 2. Here is the answer of force in general, dear children. Now I will show you how to apply it in a circle.

[01:17:08]Those who want to apply in the circle should comment in the comment box.

[01:17:13]For those who don't comment, I'll say it again.

[01:17:26]Whatever test we have on Sunday will be completed by Friday. The test will be based on whatever we complete by Friday, not Saturday. There will be no test on what I teach on Saturday.

[01:17:43]Twice MV / T sin θ / 2 Twice MV/ T sin θ / 2 Oye hoye sir hoye hoye, who is that regretful person who does not comment on this session or such content, I always regret that, no no no, not the question now, now we will come son, in this I will teach on circular motion, oh oh sir, teach circular motion also, come on son, now the body is going, it has become a ghost, sir, where has it become a circle here.

[01:18:29]He has become a ghost. We will increase this a little. We will circle this. Okay sir, show me this nice circle. The body is going, sir. From here to Oi Voi Wahi diagonally opposite. Velocity is given by tangent to the circle. Here the velocity was V. Here the velocity was V. Has that already happened? No, that has already happened.

[01:19:03]Let's put the force into it. The particle was here. I reached here. Take out the force. Hey, take out the force. What is the formula of force, dear children? What formula did I write? Twice mv / t sin θ / 2 Twice mv / t sin θ / 2 This is A part A part So I wrote why do I have to write it again and again? Now look dear children, what is theta? Angle between two vectors. Look, vector one above crutch, vector two below crutch, theta is 180.

[01:19:42]In this case, theta is 180 upward and downward.

[01:19:46]Put 110 here. 180/2, 90 sign 91.

[01:19:51]Sir, again you came, twice MV/T. Sir, this will become sin 90. But, t is also not a given, you have to remove t. Good.

[01:20:05]Okay sir, okay sir, how will we find the time, sir, find the time from here to here, time is uniform speed, uniform speed is speed, equal to half circle sir, πr, full circle 2πr, half circle πr and time t will come, sir, πr / v will come, sir, substitute here, sir, force will come twice mv and time will come, sir, pi r / v and will go up, sir, force will come twice mv² / πr, here is our answer sir, now dear children, okay sir, this was easy, this was easy, this was easy, okay, please calculate it for me in this, oh come on son, let's do the B part, now you do the work, this is a circle, okay sir, this is a circle, from here till here, take the particle, from a to B, it is a quarter circle, come on son, calculate it, give it, give it, equal in the same way, calculate the force, give it, give it, child. Okay sir, I just have to find the angle.

[01:23:19]One velocity up, the other right.

[01:23:22]One velocity up, the other velocity right. Sir, theta between them is 90. Okay sir then the formula sir the formula of force will be twice mv / t sin of 90/2 which is sin 45 which is equal to 1/2. Excellent. Now I have to find time.

[01:23:41]This is the quarter circle. Okay sir. Velocity will be 1/4 of 2πr / t going full circle 2πr crossing quarter circle 1/4 of 2πr to two with t crossed and came out πr / 2v ok substitute here what will be the force twice mv / 2 and what is the value of t πr will go up 2v.

[01:24:15]So you get 2 is 4 / 2 mv² / pi * r. If you want to solve further then rationalization is multiple by 2 divided by 2, then it becomes 2 2. The force you will get is 2 mv² / π * r.

[01:24:42]Okay, just do it like this. Get this done. Get this done.

[01:24:52]Whom? The particle went from here and came here. Let's go kids.

[01:25:26]Come on kids tell me dear children what will come sir what is the formula of force what is the formula of force what will come out the formula is twice mv / t sinθ / 2 twice mv / t sin of θ / 2 this is it sir first thing this above this right one above one right sir theta is 90 90 / 2 is 45 right so twice mv / t sin 45 is star children 1 / 2 now we have to find the value of t whose value t ok 2πr of full circle this is from here to here dear children this is not even a quarter circle this is 3/4 of circle this is 3/4 of circle children this is 3/4 of circle from here to here so you will say sir velocity is distance 3/4 of circle divided by time t what will come 2 3/2 / V what will come? f What will come, dear children? Twice mv / 2 What is the value of t? 3πr / 2v it will go up. Okay [nasal sound] Sir 2 will give 4 okay mv² divided by 3 2 πr further solve rationalization multiple by 2 divided by 2 ok then with 2 2 2 it will go to 2 2 / 3πr you can do like this this is not a big issue now the issue is let's go in this the angle was well given [nasal sound] I will show you its last part dear children.

[01:27:23]Now dear children, the particle, from some general point, was here and went here.

[01:27:29]Correct? It traced the middle angle theta. This will be the formula. Force formula mv sin θ / 2 / t right? This is what will come. Now the question is how to remove t? This was the formula that came, right? Yes twice mv/t Yes twice mv/t is twice mv/t sin θ/2 This is what was coming. Come on dear children, now the issue is t. Now see dear children, if the circle is full, it will be a full circle i.e. 2π radians. Keep a close watch, dear children.

[01:28:12]If the circle is How much is a circle? 2π radians. Yes, 2π radians. So, what is the time of 2π radians of the fourth circle? The time for the entire circle is distance divided by velocity. So the time will come, this is the angle, this is the angle and this is the time. Sir, the entire circle means when the angle is 2pi sir the time comes to 2 pi r/v, there is no doubt in this. Hi Sir, there is no doubt in this.

[01:28:45]Sir, I understood this much. Why should I join, son, what will one be equal to? 2π r / v will come down to 2π 2π 2π cancel if theta is one then r / v dear children so if angle is one then time will be r / v now if angle is theta theta is theta from here also theta from here also theta time will be r theta / v so this is time so to trace angle theta time will be r theta / v ok sir so time came for us r theta / v ok dear children substitute the force formula twice instead of mv t rheta / v here we will get sin sin of θ / 2 see dear children I will raise v up this mv² and lower it down. You keep an eye on what force will come?

[01:29:56]Force will come mv² mv² down r see mv² r I will bring this two down.

[01:30:06]Here I will write sin of θ / 2 and below I will write θ / 2. What a nice formula this has become. If you remember this formula, by directly substituting theta you will get all the results, you know everything, so this is it dear children, force mv² / r sinθ / 2 below θ / 2, with this formula you will be able to solve all the previous questions, no matter how many questions you did, in the first case theta was 180.

[01:30:46]But here the angle is in degrees and below it is in radians. Below is in radians because it's the only angle here.

[01:30:53]What's right? Is it so clear? Look son, if you look at the force, what has come out? What did the force turn out to be? The force you get is mv²/r here's sin of θ/2 and also down to θ/2 above theta in degrees. But this force will be in radians, dear children. If you want to find acceleration, find the mass in force.

[01:31:17]Acceleration has to be calculated v² / r will come here dear children sin θ / 2 will also come down θ / 2 okay dear children this is the last question of today's session, with this I will wind up this session see son this question of this pattern has probably come in JEE Advanced pattern but this is a question of Singles Physics U shaped smooth wire this U shaped smooth wire has semi circular bending semi circle bending between A and B between A and B edge shown in figure now the bead of mass m is the mass of the bead m from here the bead is one i one bead is like a ring its mass is m it is going like this kur kur kur okay enters the wire semi circle entered near A entered near B you have to find the average force from A to B what shape is it from A to B semi circle oh baba that's it that's it The question is, hey hey dad, how will you find the force in a semi-circle? Look at the velocity here of the semi circle, near A the velocity will be here.

[01:32:47]I will make it below. B will have velocity here. Velocity here, velocity here, question is over. Hey hey Baba, the question is over. Theta will be 180°.

[01:32:58]180° Okay sir. Formula of force is twice mv / t sin of θ / 2 this is it the formula theta value is 180 180/ 2 90 sin 91 so what is the force dear children twice [nasal sound] mv / t how will you find it dear children the time from here to here is a half circle its radius is a half circle we will assume r is half of the diameter sir the time of half circle will be 2 pi r 2r where will it come πr will come ok ok ok son ir distance divided by velocity v ok sir twice mv time will come πr and v above twice mv² / πr very good excellent son excellent twice mv² / πr but you have to find the answer in two and a half meters this is the answer. The value of r is the half-f diameter. So you can take it out like this also.

[01:34:04]Twice mv² instead of pie r will write diameter by two will go up. 4mv² / πd This is your answer dear children.

[01:34:21][nasal noise] Okay, dear children? 1 minute. 1 minute.

[01:34:27]Before saying thank you, I will show you which cases I discussed.

[01:34:31]I will not write the formula. Look dear children, the different cases that we discussed. Number one was ball falling. Yes, the ball is falling from a height. Ball falling from height. There were two or three cases in its interior.

[01:34:48]We read that separately. The second was the cute kids ball striking valve. Yes. Ball striking wall done two. Okay sir, look at the third case in this also, brother, talk at a straight angle.

[01:35:02]Then there was the floating disc.

[01:35:05]Remember how to make the disc float? The fourth case was a flowing water jet. Flowing [nasal sound] water jet. Good. Fifth was gun firing bullets. What was it? Gun firing bullets.

[01:35:26]Okay, and case number six you saw circular motion when there was circular motion. So dear children, these were the six big cases in which the examiner has these things available in the law of motion in which he can ask this question.

[01:35:45]Apart from this, what will happen in the seventh case which we will discuss tomorrow? Force will be given and the question will be of kinematics.

[01:35:55]What will be the question? Of kinetics.

[01:35:58]Force will be given. You have to find the displacement, find the position, find the velocity. There are many questions in Main and Advanced. So this saves us one thing. With that, our second law will be concluded tomorrow. Along with that, I will also finish Impulse tomorrow. This was the main part of the laws of motion. Then there's the plea block system, it's not as good as this one.

[01:36:23]Children, this definitely raises a question. This definitely raises a question. So everyone who is here attended the session. I see that many children here are online and watching our session. Comment that too in the comment box. We will also know.

[01:36:41]No, here's what the kids are going to see.

[01:36:49]Okay kids, come on kids, quickly comment in the comment box for the last time and share these videos with your other friends, relatives, friends who are studying in 11th, studying in 12th, those who are preparing for NEET. Only then will there be any benefit. Only then will the children benefit. Only then will it be beneficial.

[01:37:33]Okay baby guys? At the end, please put two or three comments. So with that I will wind up this session today.

[01:37:43]Today's session dragged on for quite a long time.

[01:38:45]Come on guys, let's wind up today's session here.

[01:38:48]Inshallah, see you tomorrow. Till then Allah Hafiz.