Railway Exams 2026 | Railway Physics Practice Set | RRB 2026 Exams Preparation With Ankur Sir

[00:00:19]Good Morning. Good Morning. Good morning everyone. Hello everyone. I hope that all of you are absolutely fine, healthy and well and you are able to see and hear me. So tell me once, today our practice set is number 30. Have you done 12 practice sets before?

[00:00:38]How many children are there who have completed all 12 practice sets of the previous one?

[00:00:42]Practice Set 13. What will we do today?

[00:00:45]Speed ​​velocity, work power energy are their mixed questions. Because we have asked questions on speed velocity as well as work power energy. We are finishing these today by mixing them.

[00:00:54]Then in tomorrow's class, which will be our next class, we will ask questions from the topics of mass, weight and density.

[00:01:03]From the topic of mass, weight and density.

[00:01:06]So I hope you have seen all the practice sets in the past.

[00:01:10]Aditya Sharma ji is saying, Radhe-Radhe.

[00:01:12]Bajrangi is saying, yes sir. Sir, Bajrangi does everything. There is no doubt in this.

[00:01:16]So in today's class, we will once again mix two topics of mechanics and ask questions. So today we will finish it.

[00:01:26]So we've done four electricity practice sets in class. We've done four heats. So electricity and heat became two big topics. We did it with speed and velocity.

[00:01:35]Work Power Energy practice set was installed. Today we will apply a mix of these. So our four topics of Physics will be completed. And you know all this that we have already done the theory in the class.

[00:01:45]You might have seen this one shot on YouTube so that you can get a good idea of ​​the theory. Jagdish is saying that everyone is doing it. Amit Kumar Thakur is also very good. Ok. So Jitendra, Ram-Ram brother. Arjun Yadav ji is saying good morning. The Mix Blog Aamir Priyanka Krishna Hello everyone. Deepak ji, it's okay.

[00:02:04]What do we do now? Let's get started and keep your practice so good.

[00:02:10]Keep the level up to here. That means when the question comes in the paper, while doing it you will feel that this is a real cakewalk. What level have we studied?

[00:02:17]We have to get this feeling while doing it on paper. Ok? So let's look at the first question of today, we will do it carefully first.

[00:02:25]Write the question number. Then we will write A B C D further. Ok?

[00:02:30]Tuna Yadav ji is saying hello brother.

[00:02:33]hello.

[00:02:35]Ankit is saying all complete. Ghanshyam Radhe-Radhe brother. Radhe-Radhe. Aushadh Yadav ji is saying Radhe-Radhe that in which of the following positions force is not required to keep it? He is saying that which of these cases is it, if we have to maintain it then we will not need force.

[00:02:51]So in the first one it has written that particle going in a circle. Son, if you want to move a particle on a circle. So look here, when a particle moves on the circle, its direction will continuously change. At this point its direction will be towards here. At this point here and at this point here. At this point here, you should know that Newton Bhai Saheb has told us one thing that no object can move on its own, nor can it stop on its own, nor can it change direction on its own. If a particle moves on the circle, its direction will continuously change. So to change the direction we need some force. We call that force centripetal force, that is, to maintain the circular motion, we will need centripetal force. That means this cannot be my answer because he is asking which is the case where force will not be required.

[00:03:41]Well, take a look and I found out that this is also wrong. Brother f = is in m if I want to create acceleration inside an object.

[00:03:48]Acceleration means that if you want to increase or decrease speed or change direction, then force is definitely required. This also went wrong. The third one is saying that the momentum of the particle is constant. Son, if you want to keep the momentum of the particle constant then you do not have to apply any force. Look, momentum is mass * velocity. If you do not apply any force on an object, its velocity will neither increase nor decrease. If the velocity remains the same then the momentum will also not change. So this is the condition of momentum conservation.

[00:04:14]If you want to keep the momentum constant of the particle then no force should be applied on it.

[00:04:18]If you apply force on an object, its velocity will change. That means the momentum will also change. If momentum is to be kept constant, then the net force must be zero. So the kid who was telling D got it wrong brother.

[00:04:32]I asked this question because the word acceleration came up here. So ALP students, keep in mind that in the paper, he has given such speed velocity topic where acceleration is on its own. But he asks questions like this too. So we will understand carefully. What did I say? If I want to move an object, I will not apply any force.

[00:04:51]If force is applied, the object will accelerate.

[00:04:57]Force is also required for circular motion. Force is also required for acceleration and force is not required to keep momentum constant.

[00:05:03]Question number eight will come next. This is the question from your paper. Do this, Jitendra ji is saying that it has already gone wrong.

[00:05:12]No problem. First the eyes, nose and ears should be opened. Preeti Yadav Creation SKV Rider Rishi Mishra Priyanka Yadav, Aamir, Bajrangi, Manish Kumar Karo Bhai All. It is said that one morning early in the morning, when there was no traffic on the road, Rahul noted the total distance covered by bicycle from Red Fort to his residence and the total time taken to reach home. So this child went from his home to the Red Fort. He is saying that if the total distance and total time are noted then what can be known from this? Son, if you know the total distance divided by the total time, then we can directly find the speed.

[00:05:49]Brother, velocity requires displacement. That means he will have to go in a straight line from his house to the Red Fort.

[00:05:56]So he did not measure displacement. He measured the distance. So what can he do from a distance? He can measure speed by dividing distance by time.

[00:06:03]He did not even know about the rest of the displacement, nor did he know about velocity and acceleration, he has to see how much change has occurred in his velocity, he does not even know that. All he saw was that he rode a bicycle for 5 km. It was far away, if it took 1 hour then the speed would be measured at 5 km/hour. Ok?

[00:06:20]Question number 16: I will make you do this in class. Let's see which children are paying attention to this question. Do this brother.

[00:06:28]All Amit Kumar Thakur Jagdish give us very beautiful answers in the class.

[00:06:33]very nice.

[00:06:36]Babu is asking us this question about physical quantity which has a direction. A physical quantity that has a direction.

[00:06:42]If there is any physical quantity that has direction, what would it be? So son, I told you that if any physical quantity has direction then it can be a vector quantity.

[00:06:52]She will be 100% vector.

[00:06:55]Having a direction does not necessarily guarantee that it will be a vector. If there is direction then it can be a vector.

[00:07:04]What happens generally? Those that have direction are vectors. But so must means that it is not 100% like that. As I have told you that electric current has a direction.

[00:07:14]But is electric current direction a vector quantity? No.

[00:07:17]That is a scalar. So generally, those which have direction are vectors.

[00:07:21]But there are many cases where there is direction but the quantity is still not a vector. So I told you whether a quantity is a scalar or a vector. It actually depends on which rules she follows. Look, scalar quantities are scalar quantities that follow basic arithmetic, which simply adds and simply subtracts. Like what is five and three? Eight. What is eight and eight? 16 means the very simple arithmetic that you studied in class 3 which is simply addition and simply subtraction, it is a scalar quantity, so current works the same way, at some point I had told you that suppose a current of 4 amperes came from here, a current of 5 amperes came from there, then the total current will be 9 amperes, so the current is following the basic arithmetic that a current of 5 amperes came from one side, a current of 4 amperes came from the other side, so the total becomes 9 amperes, so while the current has a direction, but it follows the basic arithmetic, hence it is scalar, we do not need to study special mathematics to add or subtract current. There is no need to read separate files. So that's why it comes under scalar quantity. So son, keep in mind that if vector quantities that have direction are vectors, then generally they will be 100% vectors.

[00:08:31]Not necessary. The one with the direction saying that it must be 100% scalar. It is not like that brother, many forces have direction, so they are vectors. Displacement has direction, it is a vector.

[00:08:41]So those who have direction are vectors in 90% of the cases but it is not necessary that they will be vectors 100% of the time. Ok? Coming to the next one.

[00:08:50]If you have read and listened to the previous question very carefully, then you will be able to solve this question.

[00:08:59]Take theory classes. Nitin Devgan is saying that Preeti had given the wrong answer first.

[00:09:05]Look, this Nitin Bhai does n't care about himself. He doesn't know about his life, that he is sitting on a broken cot.

[00:09:12]Bhaiya, this has to be converted into a bed. Converts into a large sofa. The roof is raw. The water belt might be cooking or there might be another waist built on top of it if it is cooked. This means that Preeti's first attempt went wrong.

[00:09:22]He has to pay attention to this.

[00:09:24]It is saying which of these statements is correct? First he wrote that scalar quantity can be added according to the rules of mathematics.

[00:09:31]Scalar quantities are added according to the rules of arithmetic.

[00:09:33]I told you that scalar quantities are those which follow the rules of arithmetic, which follow the basic rules which we have studied since childhood. This is correct. Why is the rest wrong? It is saying that the magnitude of displacement of a particle can be greater than the distance travelled. No.

[00:09:48]Displacement can never be more than the displacement distance. The displacement can either be equal to the distance or smaller than it. The third is saying that if a moves with respect to b then b at rest with respect to a does not. If A is moving with respect to B then B will move with respect to A. This also went wrong. It is saying that a physical quantity which has direction will be a vector.

[00:10:07]No. If there is direction then it can be a vector. It will be a vector only. This is wrong. The first answer is correct. Let us see that these are one of a kind. Well, I don't know you guys, I never tell you about myself like this and I still remember when I was studying in 12th class, my mother would forcefully slap me and send me out, I would go for a walk and I would sit and study for a while, many times I would get so engrossed that whenever I would sit, the bedsheet under the bed would shrink and I would not know how many hours had passed and I would feel that friend, it is our job to study, then why are our family members taking so much extra care of it, brother, now I don't know, when I see the children of today, I feel that it was indeed a big job brother. Nowadays we don't have patience for even an hour.

[00:10:55]Your patience is getting worse.

[00:10:57]One reel bet is watching reels and every new content is coming after 30 seconds.

[00:11:03]So there is something new to see every 30 seconds. Will come on question number 18. It is saying that if a body travels with constant acceleration, what will remain stationary? If a mass has constant acceleration, then you have to tell what will remain constant.

[00:11:30]Yes, look, these children have their exam in Basic Science from 28th July, so I don't think you will face any problem.

[00:11:37]I am telling you ALP students about your engineering topics, now the whole game depends on how well you have done them and Group D students know only general basic science, they are most comfortable with it, if you are not in physics then come and catch me, you will feel most comfortable in that, the entire theory class taught by us also says that if a body travels with a constant speed then what will remain stationary, son, see keep in mind, time is never stationary, time does not stop for anyone, time has stopped only once till date when Lord Krishna gave the teachings of Geeta, otherwise time does not stop, time keeps moving forever, now it has said that what will remain stationary when it travels with a constant acceleration, so son, acceleration means the rate of change of velocity, so acceleration means that there will be a change in velocity, there will be a change in velocity, this cannot happen at all brother, there is acceleration of a body, suppose the constant acceleration of a body is 2 meters per second square, then what does acceleration two mean that the speed will be increasing by two every second Or if the acceleration of the particle was -2, it would be decreasing by two every second. So if there is acceleration, then acceleration itself means the rate of change in velocity. The velocity will definitely change. Well, if you are going at a constant acceleration, every second your speed is increasing by two, so your displacement is constantly changing.

[00:12:50]That means what is the answer to this? None of these.

[00:12:54]Now that I see it, I felt very bad. The child who wrote its answer B. That means the person who is writing this, that is, what a useless concept it is, he does not know that when a particle has acceleration, acceleration itself means that there will be a change in its velocity. Rate of Change in Velocity The rate of change in velocity is how fast the velocity is changing. How fast is the velocity changing? This is acceleration. So if there is acceleration then velocity cannot be constant. If the velocity is constant, that is, there is no change in velocity, then the acceleration is 100% zero. Then this brother ticked answer B of whatever the children wrote.

[00:13:34]We will wait for two-three seconds and you will pull and slap your ear.

[00:13:41]And don't think that just by saying this you will sit down.

[00:13:43]No, I have to kill him. You are telling me the answer to this. This is a great sin. This is such a sin whose punishment is not even written in Garuda Purana. Have you ever heard of Garuda Purana or not?

[00:13:57]Next comes question number 27 which says we have to match List A with List Two. Do this and kill me. very nice. Hit it so hard that the family members come running. What happened?

[00:14:14]What happened?

[00:14:16]This is written scalar vector this is written something. Well, you all know that mass is a scalar quantity.

[00:14:23]Mass is a scalar quantity which has no direction.

[00:14:27]Whether the mass of an object is 2 kg, 5 kg, 6 kg, there is no direction. So one will come with A. Hey look what a dirty option has been made. The one who made it, the creator himself, what can I tell you? Just look at the first one, there is no need to look at the rest.

[00:14:39]Well, you know that son velocity is a vector quantity.

[00:14:42]Vector quantity So what happened with this? It came with b three. Now comes the scalar product and vector product. Scalar multiplication and vector multiplication.

[00:14:53]Remember, when we taught you the topic about work, what work did we tell you about? Of force and displacement. This is the scalar product of force and displacement. There is a dot between force and displacement. So the work done is the scalar product of force and displacement. These scalar products are scalar multiplications. So what will come with C? Four. Now son, the torque, the force moment, is written as tau. So the torque is R vector cross F vector. The cross that appears means vector multiplication vector product. So torque is a vector product. Vector multiplication.

[00:15:30]So I took this question because it is asked in the scalar vector paper.

[00:15:34]Velocity is also work power energy in your topic.

[00:15:37]Well, these monthly things are already understood. So vector quantities are those quantities which have direction, in general there is no 100% confirmation. Scalar does not have any direction and if there is a dot between scalar and vector multiplication i.e. two vector quantities, then scalar multiplication will be formed i.e. scalar will be formed. There is a cross between two vector quantities, which means that a vector will be formed. Is this ok? So torque, which is the moment of force, is vector multiplication.

[00:16:09]Do this the 29th. The following energy is always positive. Which of the following energies is always positive? This will do it.

[00:16:17]V Energy Always Positive.

[00:16:23]One is saying that when I get free from Instagram Purana, I will read Garuda Purana.

[00:16:27]Garuda Purana is not meant to be read. When a very elderly person dies in any street or locality, then Garuda Purana is recited. And man, take her very seriously. Cannot commit sin in life.

[00:16:37]Whoever listens to Tak Run Purana once, his soul trembles from within.

[00:16:43]It is saying which energy is always positive. Remember, kinetic energy can never be negative. Brother, the kinetic energy is 1/2 mv².

[00:16:53]Now, any object never has mass.

[00:16:56]That the mass of an object is -6 kg. Have you ever heard it? No. And this value of the square over v will also always be positive.

[00:17:02]Kinetic energy is always positive. This potential energy etc., we see it at the height from the ground.

[00:17:10]How much higher it is, the potential energy is positive. Suppose I am measuring potential energy from this line. So whatever is above it will have positive potential energy.

[00:17:17]Whatever is below will become negative. So all the other energy depends on the reference line from where you are looking at the height etc., so it can be negative. Kinetic energy is always positive. So kinetic energy can never be negative.

[00:17:30]Which of the following is the velocity-time graph of a car moving in uniform motion? So what graph is telling me is that there is uniform motion. Let's say we have the x axis.

[00:17:44]We have it in y.

[00:17:47]We have this on the x axis.

[00:17:52]This is this is y. Ok? It is like that.

[00:18:05]So son, see one thing, it is saying that which graph is for uniform motion, for uniform motion, so for uniform, firstly our graph should come in a straight line, the one which is coming in a curved line, this curved one is wrong, leave it out first of all, secondly you can also see this brother, the velocity which is increasing and decreasing with time, increasing and decreasing, this is also wrong, now see or did I tell you what is the method of understanding any graph?

[00:18:32]You can take two points anywhere on the line that you see on it.

[00:18:35]Take two points wherever you feel like.

[00:18:37]And then I said, what will you do?

[00:18:40]From the first point, we will draw a line on the x axis and another on the y axis. From the second point, we will draw a line at x and another at y. So here you can see that time is written on x. The time changed from 1 to 3. Times are changing.

[00:18:51]But there is only one cut here. So the velocity at 1:00 is the same at 3:00. So this is a uniform velocity graph. Here you see, the velocity was this much at 1:00 pm and what was the velocity at 2:00 pm? The times are also changing. Velocity is also changing.

[00:19:05]So this is also not a graph of uniform speed.

[00:19:06]So what answer will we have to this? A option. It was an easy question. Well, let's enter any question number.

[00:19:14]How many are there?

[00:19:16]Consider this 7 8 nine. Isn't it?

[00:19:21]Nine.

[00:19:24]Question number 10, this is a beta question, that is why I have taken this question, it can be found in some set or the other in the paper, this is a good question, someone has also told the answer, oh yes, Sanjeetha Singh ji is telling the answer of the previous question, S K B, son, this second one, this graph would have been a uniform speed graph if distance was written here, then you would have said sir, time is also changing, distance is also changing. That means the object is in motion and is in a straight line. That means the motion is uniform. Son, do you know why you are getting confused? Those children who have ticked B.

[00:20:01]This graph would be of uniform speed if I were to draw it like this here. Don't memorize the graphs.

[00:20:08]See what is written on the x axis?

[00:20:09]What is written on y? If I write distance here, distance or position.

[00:20:14]Distance distance distance should I write here time.

[00:20:17]So if I graph this one, it will become a graph of uniform motion. This is because the two points you will take are changing time. The distance you travel is also changing. You were at home at 1:00 and went to school at 2:00. That means you are running away.

[00:20:32]Are in motion and in a perfectly straight line.

[00:20:34]So this is the uniform motion graph. This is also a graph of uniform motion. But this does not mean that whenever such a graph is formed, it is of uniform motion. There should be distance here and time here. It is written here that velocity is changing time. The velocity is changing. Where did uniform motion come from? This is the graph of uniform motion. Yes, if position distance was written here then what would you have said sir, time has changed but the position remains the same. So this graph would have been at rest.

[00:20:55]This graph would have been of resting state.

[00:20:57]If position, distance, displacement etc. were written here, it would mean that time had changed. The distance you travel is not changing. Your position is not changing. So this graph would have been of rest. If this graph here were distance and time, it would be of motion. It would be of uniform motion.

[00:21:08]But son, look here, what is written here? This is not rote learning. If you study from us and then just rote learn, then what is the benefit? Then whatever you have read is enough. Saying that the motion of the body is an example of uniformly accelerated motion. He is saying that which of these motions has acceleration or accelerated motion. That means the speed may be increasing or decreasing or the direction may be changing.

[00:21:30]So son, rest is not a quick movement.

[00:21:32]This is continuous rest so there is no change in your speed. There is a change in direction. One is saying decelerating. One is saying parabolic and one is saying free fall. See, when an object does free fall, its speed increases every second and that acceleration is absolutely constant. When you drop a stone, its speed increases by 9.8 every second.

[00:21:57]I am talking about 9.8 Earth. So, in free fall, when any object falls, its acceleration is constant, it is uniform and that constant acceleration is equal to g i.e. 9.8 meter per second square. So, free fall is an example of a constant acceleration, say uniform acceleration or constant acceleration. Acceleration may occur in other things but it is not necessary that it is constant. So, when any object does free fall, then the object is accelerating, that is, it is falling down, it is accelerating, the speed is increasing, but the acceleration it is doing is uniformly. The speed is zero now, after 1 second it increases by 9.8. Then it increased by 9.8 and reached 19.6. So every second the spot will move 9.8 by 9.8. So remember that free fall is an example of uniform acceleration. Let me see who will do this question number 11. Let's do 11. 11 We have Indra Prakash ji, Manoj Kumar, Preeti, Story Keeper, Bajrangi, Sanjeetha Singh, Shobhit S's driver writing some answers. Question number 11 came to me. Saying an object with a constant speed. If the speed of an object is constant then Bablu Bhai's mistake was made right from the beginning.

[00:23:10]This is also wrong with Yadav Creation ji.

[00:23:14]Anil has also made a mistake. Manoj Kumar's statement is also wrong. All the other children who are writing C are fine. Son, I understood the meaning of this, which of our children has studied and which has not. It says that the speed of an object is constant. Son, the speed is constant, that is, neither the speed is increasing nor the speed is decreasing. I told you this.

[00:23:35]But I did not tell you anything about the direction. Said that the speed is neither increasing nor decreasing. Now there can be two cases here that the direction may not be changing.

[00:23:44]Son, neither the speed is increasing nor the speed is decreasing nor the direction is changing. That means there will be no acceleration then. So this is saying that there will always be acceleration. This went wrong.

[00:23:52]Well, neither the speed is increasing nor decreasing. It is possible that the direction is changing, so changing the direction is also acceleration.

[00:23:57]So it will not accelerate. This also went wrong. Son, if the speed of an object is constant then the object can accelerate.

[00:24:04]Brother, speed is the only constant. I do n't even know the direction. Brother, the speed is neither increasing nor decreasing. It is possible that the direction is continuously changing, so even if the direction is changing, there is acceleration, if the speed is constant, then also the acceleration can be 100% only, this is wrong brother, the speed is constant, the acceleration will be 100% only, why is this wrong, who knows, the direction may not be changing at all, why is that correct, because the speed is neither increasing nor decreasing, then why is it wrong that the direction is changing brother, the speed is constant, speed constant does not mean that the velocity will also be constant, velocity is constant when neither the speed changes nor the direction, what is velocity, speed * direction, so if the speed is constant, then the velocity will be constant. It is not necessary.

[00:24:43]Velocity is constant when neither speed nor direction changes. And the problem is that we have not been told anything about the direction.

[00:24:50]So what many children think is that if the speed is constant, they think that acceleration cannot happen. Brother, even if the speed is constant, acceleration can still happen.

[00:24:59]If changing direction. But if I write constant velocity in this question, then constant velocity means neither the speed will change nor the direction will change, then you will say that there will be no acceleration, then your answer will be B, write it in your copy in the notes, if the speed is constant, if the speed is constant then there can be acceleration, who knows it may be changing the direction, changing the direction is also acceleration, but if the velocity is constant, if the velocity is constant then the acceleration will be 100% zero, we have made the children write this clearly in the class that if the speed is constant then the speed is constant. If the speed of a particle is not changing, it is called constant speed. If the speed is constant, then acceleration may or may not occur. It may or may not happen. May be excited or not. Acceleration may or may not occur. If the speed is constant, but if it is said that there is constant velocity, then the acceleration is 100% zero. Constant velocity means neither the speed changes nor the velocity changes, sorry, nor the direction changes. Constant velocity means neither the speed changes nor the direction changes, so the acceleration is 100% zero.

[00:26:16]Make your notes and read this carefully in all the papers. If there is constant speed, then there may or may not be acceleration, but if it is said to you that the velocity is constant, then there will be 100% acceleration zero.

[00:26:31]Ok? Come next. Question number 12.

[00:26:39]Look, I have just asked this question. This same topic is being discussed in the batch from 7 to 8 in the morning.

[00:26:43]If there is a child then give the correct answer to this.

[00:26:50]A child is saying that Jai Hind Sir, we studied Physics from you in ARO batch. I selected ARO in Unnao Police. Oh wow, that's great. Congratulations brother, what is the name of this child, Kop has gone ahead, Kop Tejas, congratulations, yes, the story keeper has the same condition for velocity, it is saying that it is moving on a straight path with instantaneous speed, son, look now look here, it said that the particle is in instantaneous motion but is moving on a straight path. Now tell me one thing.

[00:27:18]When we gave you a one-shot of speed and velocity or taught you in class, we told you that if the particle is in rapid motion, accelerating, then it has three meanings. Either the speed is increasing or the speed is decreasing, the direction is changing.

[00:27:31]Now he said that the direction is not changing.

[00:27:33]Walking on the straight path. Now the direction is not changing. That means the speed should be changed.

[00:27:37]So it is saying that if the particle is in accelerated motion then its speed will change. This is true. But we don't find the right one. We have to find the wrong one. So this cannot be my answer.

[00:27:43]Good. Well son, if the particle is in accelerated motion, acceleration means change in velocity. If the velocity changes, then the velocity will change. This is also correct. If the particle is in accelerated motion, then a force will definitely be applied on it.

[00:27:53]f = ma. Newton's second law.

[00:27:57]Acceleration is produced when force is applied. This is also correct.

[00:27:59]But if a particle is in accelerated motion, it is not necessary that it will be moving away from the earth. Brother, tell me one thing. If I have a marker in my hand, is it coming closer to the earth or running away from the earth? You will say, Sir, it is coming closer to the earth. Is it not accelerating? Of course it is.

[00:28:12]Its speed is continuously increasing. The increase in speed is acceleration. So its answer will be option B. It is asking us which one is not correct? So if an object is in circular motion, it may be in circular motion even when it approaches the Earth. The circular motion can also occur while moving away.

[00:28:27]And in circular motion it does not mean that it will be moving away from the Earth.

[00:28:31]So B went wrong.

[00:28:36]Hey, are you understanding anything or not? Is it Aro or the same thing that Maa Saheb, you really don't understand anything, is there anything or not, tell me do you understand anything or not, is there anything, whenever I speak this line, I used to teach in Agra, I also used to teach at the centre, earlier there was offline phase, then a child used to come from there, this from Bharatpur side, one day in the class he was saying Maa Saheb, I don't understand anything about Aro, then I said, I am not Aro, Maa Saheb, nothing, Aro, I have studied Physics for the first time, though that is a different matter, the boy later studied in Dakshinanchal of UP, maybe he got selected in the electrical department, he worked very hard for that and I did not think at all that he could get selected.

[00:29:40]He was weak in maths and everything else but he tried and succeeded. There was a boy from Baghpat side, he became SI in UP, he used to study in Meerut centre, looking at him sir, it did not seem that a little strong and badass type person had become SI of Sega. So sometimes there are some people who later bring changes in their lives. Consider question number 13. Let 13 be saying that if both velocity and acceleration are negative for an object then its speed is saying that if both velocity and acceleration are negative.

[00:30:13]Velocity is also negative, acceleration is also negative. Meaning the velocity is -10 meters per second and the acceleration is -2 meters per second squared. So, are you saying that the speed will increase, decrease or remain the same? What will happen? I will see the answer to this. What will you give for the 13th?

[00:30:29]Golu, Manoj, all of us children are writing answer B for this, slap and pull you again, it seems you will sit at home with red cheeks today, son, see velocity is also negative, acceleration is also negative, you are just looking at acceleration, do you know what both negatives mean, negative in physics only tells the direction, velocity negative means that the particle is running in this direction and acceleration is also negative, that is, you are accelerating in that direction, you are pushing in that direction, so wherever there is velocity and acceleration both are in the same direction, then the speed increases.

[00:31:03]Now what is the problem with the children? They consider negative acceleration as a decrease in speed.

[00:31:07]Son, if the acceleration is negative then the speed is considered to be decreasing only if the velocity is positive. This means that the particle is moving in this direction and you are pushing in the opposite direction. See if both of them have the same sign. Even if both are positive, the speed will increase. Even if both are negative, the speed will increase. One of these is positive and the other is negative, that is, both are in opposite directions. It is also possible that I take velocity as negative and acceleration as positive. The speed will decrease here also. Do n't think that acceleration is positive, sir. Because I have told you about velocity. Velocity and acceleration are both opposite. The particle is moving towards the west and is being pushed towards the east, even then the speed will decrease. If both have the same sign.

[00:31:43]I taught this in class today.

[00:31:45]Those children know this in great detail.

[00:31:46]I spent at least 15 minutes in this pay class explaining the concept of if velocity and acceleration are in the same direction. Whether both are positive or negative, the speed increases and if both are positive and one negative, both are in opposite directions, the speed decreases.

[00:32:03]Question number six: Do whatever is written. Will do it.

[00:32:11]Which of the following statements is correct? Let's do this. The one with B is in the sack, which means that if the competition wants, the teacher can reduce the number of questions. How can those who have studied something from here and there make it?

[00:32:31]If I make 20 questions of Physics, out of 20, those who do not have clarity of the concept will make 17-18 wrong, but when the teacher makes the paper, he makes it in such a way that it seems as if all the five, seven or eight questions have been done. So whatever questions the children ask are those which the teacher wants you to do correctly. So those who have worked hard and given time, they get 18-19 out of 20 questions correct.

[00:32:51]Which of the following statements is correct? It is saying that the speed of an object is its velocity in a given direction. The speed of an object is its movement in a fixed direction.

[00:32:59]Son, he wrote this upside down. The speed of an object is not its velocity in the direction.

[00:33:04]He had to write the velocity of an object. Velocity is speed in a given direction. Velocity, what is velocity? Speed ​​in a fixed direction.

[00:33:13]Velocity is speed * direction. Not that this is correct. Can't we write like this what is speed? Speed ​​is velocity in a given direction. This is wrong. Speed ​​is not velocity* direction. Velocity is speed * direction. Velocity is speed * direction. What is velocity? Movement in a given direction.

[00:33:31]So he had to write that the velocity of an object is its speed in a certain direction. Then it would have been correct. He wrote it upside down. It is saying that if the acceleration is positive then the speed will increase. It is not necessary.

[00:33:41]Acceleration is positive. The speed will not necessarily increase. Acceleration is positive.

[00:33:45]Who knows, the velocity might have been negative. The speed will decrease in both opposite directions.

[00:33:49]Acceleration being positive. It is not necessary that the speed will increase.

[00:33:55]If acceleration is positive. If velocity is also positive then speed increases. It was discovered that the particle was moving towards this side. If the velocity is in the negative direction then it will decrease. This is also not correct. It is saying that when an object is thrown upwards, its acceleration at the highest point is 9.8 meters per second squared. Correct. See, when you throw an object upwards, whether the object is going up or coming down, at every point, at every point, whether you take it here or here in the middle or above, at every point, its acceleration is 9.8 meters per second square. But son, if he tells you to throw an object straight up, what will be its velocity at the highest point? Zero. Throw an object up.

[00:34:30]The velocity decreases and eventually becomes zero. Acceleration occurs at every point while going up and down 9.8 This is correct.

[00:34:38]How many people have got this answer correct?

[00:34:42]Sanjay RDX is giving very good answers, his brother. Ghanshyam Rishi Rider. Hey, this is fine for many heads.

[00:34:50]Look, Rakesh Yadav Talk, the child is giving wrong answers by putting the photo of Rakesh Yadav Sir. Are.

[00:34:56]For this also a separate chapter will have to be created in Garuda Purana. I have also named him after Guru ji.

[00:35:01]Rakesh Yadav has also uploaded the photo and is giving wrong answers. We are going to start a new chapter, do this today. Take this, take anything 15. Let us say the figure below shows the acceleration-time graph of a moving body.

[00:35:21]This is an acceleration time graph.

[00:35:24]What will be the maximum change in the velocity of the body? What is the maximum change to be reported?

[00:35:29]Acceleration means that the graph is given between a and this type.

[00:35:38]Look son, he is asking me to tell you how much the change will be? Maximum change. So what is acceleration? Change in velocity divided by change in time. So son, if you want to find the change in velocity, do you know how to find it? Change in velocity is given by acceleration * time. Ok? So what do you do if you ever have a graph of acceleration and time? Find the area inside it. If you want to remove the maximum area from inside, then remove the entire area.

[00:36:07]When you calculate the area inside it, that area will give you the change in velocity. The graph of acceleration and time is. The area inside it gives the change in velocity. So we will find the inside area. So the velocity change will be given by the area under the graph under the acceleration time graph. So if there is a graph of acceleration and time in the paper, you can also directly ask that if you have a graph of acceleration and time, then what will the area inside it give? Change in velocity.

[00:36:38]Whose area looks good? Who is this line encircling? to the triangle. So what is the area of ​​the triangle? 1/2 base * height does not always make the area of ​​the triangle. If this line were like this then the area would be that of a rectangle. This is the area of ​​the triangle. So how much is 1/2 base? You will say sir the base is from zero to 12.

[00:36:55]This became a 12 second base.

[00:36:58]What is your height? Come this way. What is this height?

[00:37:00]From here to here, I have given 10.

[00:37:02]What is your height? 10 so 2 * 6 = 12 this comes to 60. Then what will be the maximum change in velocity? 60 meters per second. Also remember this directly that if I have a graph of acceleration and time, if I find the area inside it then I will get the velocity change. Ok?

[00:37:23]Velocity change.

[00:37:29]Correct? come now. Question number 11. 2000 kg A truck of 18 km. It is moving at an hourly speed.

[00:37:38]How much work will be required to stop the truck? Do this. It wo n't feel like Pythagoras. Why use Pythagoras brother? Who has to apply Pythagoras.

[00:37:59]What will he do with Pythagoras? The area of ​​a triangle requires the base and height. There should be no hypotension. Okay, are you guys coming in between? Let me do it here.

[00:38:09]Well, are there any English speaking children in the class?

[00:38:16]Suraj Kumar, Jagdish, Amit Kumar Thakur are giving good answers. Here Mithun Kumar keep on doing us. It says how much work does it take to stop a truck? I told you if you ever need to increase or decrease the speed.

[00:38:31]In yesterday's class it was told that to increase or decrease the speed we have to do work 1/2m v² - 1/2 mu² v is the later speed u is the final speed initially the truck is moving at a speed of 18 km/hr.

[00:38:46]So what is the starting speed?

[00:38:48]18 km/h. You know that while doing numerical calculations we use SI units. So to convert meters into seconds, we have to multiply by 5/18.

[00:38:56]So the initial speed became 5 meters per second.

[00:39:01]Ok?

[00:39:03]What should be the final speed to stop?

[00:39:06]How much work will be required to stop it from 0?

[00:39:08]Look here, son, the final speed has to be zero. If you want to stop it then it becomes zero part.

[00:39:13]What is the value of minus m? 2000 kg How much is U? 5² is 25, right? So if we divide it by two, we get 1000. If we solve it, we will get -2.5 * 10 ^ 4 joules. So the answer came in negative because the speed is being reduced, it is being stopped. 2.5 * 10 to the power of 4. Now it has not used plus or minus in any of them.

[00:39:33]So that means asking for empty value. It would have been better if minus was written. And we would have given a beautiful answer. He is saying look at this. I have kept this intentionally.

[00:39:45]This question is repeated a lot.

[00:39:46]It is also the energy possessed by a body due to its change in position and shape. Due to change in the shape or position of an object, see the energy contained in the object. You have changed the shape of the object.

[00:39:59]Pulled the spring, pressed it, pulled the rubber band, pressed it. The condition of the object was taken from here and taken here. So when we change the position of an object, we take it to a higher height, lower height or pull it or press it. So because of this the energy that is stored inside it is potential energy. Potential energy.

[00:40:15]Everyone knows this.

[00:40:18]Look, this is related to the previous question.

[00:40:20]This will do it. These are one or two questions that can increase the child's confidence. Do this. It is saying that a compressed spring has more energy than a spring of normal length.

[00:40:41]Which of the following happens as the spring is compressed? You know son if you compress the spring. If you compress it, whether the spring is compressed or you have stretched or extended it, then which energy does it store, it is potential energy. It is saying the unit of power used in industry. What is the unit of power used in industries? It is writing kilowatt, watt, joule, horsepower. So, you have to tell what is the industrial unit of power. Look, you should not make a mistake in haste in this. If in the paper he asks you to tell the SI unit of power, then the SI unit is watt. This is the SI unit. In the international system, we use watt. But son, he has asked about industrial, so horsepower is used in industries. Brother, industrialists will buy an engine and bring a motor. They will buy anything, they say it is of 15 horsepower, 20 horsepower, or 50 horsepower. So, the industrial unit is horsepower and one horsepower means 746 watts.

[00:41:41]Read carefully what he is asking. Is he asking SI or is he asking industrial? Is he saying if a boy covers a distance of 20 meters with a force of 600 Newton in 4 minutes. If he decides then what is the amount of power consumed by the boy? So son, I am asking you for power.

[00:41:58]Ask this question.

[00:42:02]Ghanshyam ji, please write down the question number also.

[00:42:04]Whatever is written on the board in front.

[00:42:08]Well now see here a boy covers a distance of 20 meters in 4 minutes with a force of 600 Newtons. I have to tell you the power. So son, what is the basic formula of power? Power is the rate of doing work and work up time. Now I have to get the work done.

[00:42:20]So saying that with a force of 600 Newtons travels a distance of 20 meters. That means a direct formula for work has to be applied.

[00:42:25]fs cos theta. The time is written below. So how much force is it applying? Of 600 Newtons.

[00:42:31]How much displacement is taking place? 20 meters. So if we are not given the angle, that is, if both are in the same direction, then the angle will be considered zero.

[00:42:38]How much time is there? 4 minutes. So while doing numerical you have to keep in mind that if we use such unit then our time is 4 minutes. Change it in seconds. Sometimes leave it for a minute. I will solve it in 240 seconds. Now we will divide it by 60. This Babu has come 10 4 * 5 = 20 10 * 5 = 50 value of cos 0 is 1 that is 50 watts.

[00:43:03]Answer to 27 is A Answer is 50 watts A is for all Manoj Ratansh Anil Yadav Creation Bajrangi for all ok Question number 28 Look, this question of this type has come to you in Railways, so do solve it carefully Mohan's weight is 40 kg and he climbs 50 stairs in 10 seconds, if the height of each stair is 10 cm, then what is Mohan's power? So son, look, Shakti is asking, power is work/ time. Now see what is happening this time?

[00:43:38]What was the work in the previous question that displacement was being created by applying force.

[00:43:42]Displacement was being created by applying force. We applied fs cos theta. But what is he doing this time? Who is Mohan Babu 40 kg. That they are climbing up the stairs. And what are you offering up? To your body. So how much work do we do to move an object upwards? Yesterday we read mgh. Now why was the work formula mgh applied here?

[00:43:56]Because it's going up this mgh.

[00:43:59]Our work is done. How much mass does it have? 40 kg Of. The value of G is saying let's say 10 in numerical terms. And how much is H brother? There are 50 steps and one step is 15 cm.

[00:44:10]of. So there are 50 total stairs. A ladder is 15 cm. has done. To convert a centimeter into a meter, divide it by 100.

[00:44:17]SI units are always used in numerical calculations.

[00:44:20]50 * 2 = 100 i.e. it comes to 7.5 meters. So the height will be 7.5 meters.

[00:44:26]7 means 15/2, solve it. This comes to 20 15 * 2 = 30 i.e. 300 watts will come. Find out if it was 300 watts or not? The C of the 28th has arrived. You are asking the question before me, friend. Manish Guddu your voice Bheem what is this child writing?

[00:44:52]Preeti Ratansh is great. Ok.

[00:44:57]Question number: Suppose you write anything like 20.

[00:44:59]5 kg 10 kg Two steel balls of mass m have the same kinetic energy. The kinetic energy of both five and 10 is the same. If possible, which ball is moving faster? He is saying that there are two balls. The kinetic energy of both is the same.

[00:45:12]So who is saying which one is moving faster?

[00:45:17]Look, now I have told you that the kinetic energy of both is the same. The kinetic energy is the same and asking who is running faster.

[00:45:24]Referring to speed. So what is the formula for kinetic energy in terms of speed? 1/2 mv² If we want speed, what will happen if we remove the speed? v² will become 2k / m so the value of v will come to 2k / m now look here carefully. The kinetic energy of both the balls is the same.

[00:45:42]So k is the same. Remove both of them.

[00:45:44]Kinetic energy of both is same. There are two numerical values. It's fixed.

[00:45:48]Remove this first as well. m is written, it is also written below.

[00:45:50]Above means that the one which has less mass will have more speed. So if the kinetic energies of two balls are the same, then the lighter ball will travel faster. So the answer is A for 20th.

[00:46:00]Many children first memorize that a lighter ball will run faster. Then she will run away, son, fast. Only if the kinetic energy of both is the same.

[00:46:07]If the kinetic energies of both are equal then we see that m and v are above and below, so the one with less mass will run faster.

[00:46:16]Understand? It is said that a boy of mass 50 kg is riding a scooter of mass 100 kg at a speed of v per second. v will be the speed in meters per second. He is moving at a speed of v meter per second. He is moving at a speed of v meter per second.

[00:46:44]V is driving at a speed of metre per second.

[00:46:48]Write the English ones also. V is driving at a speed of metre per second. If the kinetic energy of the scooter and the boy is 76.8 kJ, then find the value of v. See what is kinetic energy? 1/2 mv².

[00:47:03]Ok? So he is saying that he is a 50 kg boy.

[00:47:06]100 kg There is a scooter of mass.

[00:47:08]And the kinetic energy of the scooter girl is 76.8 kilojoules. 76.8 kg means 1000 joules of energy. How much is the mass? There is a boy and he has a scooter worth Rs 50. 100 means it became 150.

[00:47:20]We have to find this v². Isn't it? Now see brother, who is getting cut by whom?

[00:47:26]Not from whom? We are getting cut by three. 13 13 will be divided by three. First point was removed and zero came below.

[00:47:40]3 * 5 = 15 0 3 * 2 = 6 3 * 5 = 15 3 * 6 = 18 ok?

[00:47:49]It's a zero cut off by a zero. Ok?

[00:47:53]25 came after subtracting two, now the matter is settled.

[00:47:57]What will V² become? This 256 times 100 comes down to what? 25 so 25 * 4 100 then V will be calculated, the root of 256 will be 16 4 will be 2 16 2 32 meters per second is coming out to be 32 brother for all that 25 * 4 100 will be two here 16 will be 16 * 2 = 32 is coming out to be 32 very good okay next thing is I will get this question done, I have taken this question from a paper of Haryana, I thought it is a good question and they had kept the language a little similar so I have kept it the same, I did not change it, it is saying that the potential energy of a 100 kg block up to 10 meters along a 30° inclined plane, it is saying that the potential energy of a 100 kg block 10 meters along a 30° inclined plane, see what it has said, look carefully here it is saying that there is a plane inclined at 30° and it is saying That this is an inclined plane inclined at 30°, we pulled a 100 kg body up to 10 meters on this inclined plane, we pulled a 100 kg body 10 meters up on this inclined plane, so it is being said that what will be its potential energy here? What will be the potential energy? So son, understand this carefully. 100 kg The body has been pulled along the inclined plane for 10 meters. Now you know that potential energy is mgh.

[00:49:30]How much is M? 100 kg Take the value of G as 9.8.

[00:49:35]Because here 984900 is mentioned, then the value of g must have been taken as 9.8. Now you have to find h. This is where we make a mistake. That's why I have asked the question. What does the child do? Writes 10 meters instead of h.

[00:49:45]Son, you will pull this spindle and take it up like this. So this height is from such a big land.

[00:49:49]This formula of potential energy is how high you went above the ground. He is not the one who walked so far.

[00:49:56]Potential energy is in mgh. Then you will pull this body and take it away like this. So you have to find out how much it is rising from the ground.

[00:50:02]So if this is 10 meters, this is a 30° angle, then son, you know how it will look. sin Look, this is long. This is Karna. So apply sin. What is sin? Perpendicular to the hypotenuse, so the value of sin 30 is 1/2 h / tan 2 * 5 = 10, so the value of h will be 5 meters. h came five. So make five putts here. Ok? So this is what I got 98 * 50 because one zero is gone from the point, so if we multiply 98 by five then it will be 490 and one zero, 4900 is written, will the answer be 4900 joules, the child who will keep it straight 10 meters will get D answer, remember in this question whenever you calculate the potential energy, keep in mind that for the potential energy you have to see the height from the ground. It is important to what height you reached. I will do this question, question number 29. 29 Sanjay Look RDX got the previous question wrong. The children have also answered this previous question D. However, 4900 joules is the answer for more children. A story keeper also gave Rs 9800.

[00:51:30]This is telling us what will happen if an object is dropped from a height in the absence of air resistance.

[00:51:35]That is, what will happen if there is no air and we drop an object? Do this. In the first it is written that it will fall with constant speed. Son, tell me one thing. When you drop an object, where does its speed remain constant? So when we drop an object on the earth, its speed increases by 9.8 every second.

[00:51:55]Its speed is not constant. Yes, the acceleration constant is 9.8, so the speed will increase by 9.8 every second. This went wrong. Acceleration is constant when an object is in free fall. I was told today that the acceleration of an object in free fall is constant. It is saying that both speed and acceleration will increase. No, only the speed will increase.

[00:52:12]When an object is in free fall, only its speed increases.

[00:52:18]Who is this genius who is writing his answer C? Son, when you drop an object, its speed will increase by 9.8 every second. The speed is increasing. Acceleration is not increasing.

[00:52:27]Acceleration is fixed at 9.8.

[00:52:29]The speed will increase by 9.8 per second. When an object falls down, it does not happen that in the first second the speed increases by 9.8, then by five, then by 15, then by two, and then it does not increase at all.

[00:52:39]So we will say that there is a change in acceleration. There is a fixed acceleration that will increase by 9.8 every second. Ask this one question.

[00:52:49]This is the last question for today.

[00:52:51]What do you infer from the given velocity, time, graph? Do this. This is a graph of velocity and time.

[00:52:57]What is he telling you?

[00:53:08]According to the velocity-time graph, we have velocity-time equation. Son, in this I am saying that it is moving with uniform velocity. Velocity is not uniform at all brother, look here velocity is written, time is written. Take two points, one on the line x, one on y, one on x, one on y. So, the time changed from 1 to 2:00 and the velocity also increased. So, velocity is not constant, this is wrong. The new velocity is continuously increasing even at rest.

[00:53:31]One is saying that it has some initial velocity. One is saying moving uniformly with some initial velocity. Look, there is velocity in the beginning. There is some velocity at time zero but the velocity is not uniform. Is continuously increasing. So option B is correct in that it has some initial velocity. So there is some initial velocity, but that velocity is continuously increasing. That is not a uniform.

[00:53:49]Its answer is B. So, all the children who wrote B for this are fine. I would like to see once how many of you children got how many questions right?

[00:54:02]Once we do the question count here.

[00:54:12]How many questions have you asked?

[00:54:16]I will leave a few questions for you which you can do at home as homework.

[00:54:23]So today we have done two, three, four, total 25 questions. So how many of the 25 were right for you? Tell me what the score was.

[00:54:35]Ok? So keep reading like this.

[00:54:39]A child is saying that today I am in trouble.

[00:54:41]Why brother? There were conceptual questions. It was not all like this brother. Today there must be some great numericals. All were theoretical questions. Sir, you are explaining physics very well. I was scared. Well, in B04 batch, Rajkumar ji is writing something and writing 23.

[00:54:57]Sanjay Yadav is saying that he did not count 20. You must remember how many mistakes he made.

[00:55:05]Ishwar Jhadkar 18 21 Bajrangi how many were correct today, he got 21 correct. He got late. One child is saying, son, the class is from 8 to 9:00. The children who watch this later should also tell their score and comment and try to take out one hour in the morning. We will come from 8 to 9:00. Now, we will take the next class.

[00:55:24]Now I think the class will be held only on Monday. On Sunday I'm thinking I'll give you guys in Group D a one- shot for optics.

[00:55:34]Ok? I have an offline class tomorrow, Saturday.

[00:55:37]So tomorrow is difficult. what shall we do now? We have read three topics.

[00:55:42]We have read four topics. We read about heat, electricity, speed and velocity, work, power, energy. There are four topics now.

[00:55:49]What will we do on Monday? Firstly, I will make you solve questions on Mass Weight Density related to the Gravity chapter and the rest of the Group D students will also get one shot of Optics. Ok? So for now, keep preparing yourself, keep studying, keep smiling. We will keep meeting the rest.

[00:56:05]Ok? Bye. Take care everybody. Thank you.