 All right, everyone welcome again. So this is Dheeraj from Centrum Academy. So this is another question I've taken up that is asked by one of our students and This is from work by energy chapter. All right, so you can see on your screen The question says there is a car That way around 1400 kgs Okay, so first of all whenever you start solving the question please always While you are reading the question you should also write down the data which is given. Okay So mass is 1400 and it is moving with a speed of 54 kilometers per hour Fine and of course by now you must Be knowing that you should convert this into meter per second by multiplying with 5 by 18 Okay, this comes out to be 15 meters per second. All right So basically what happens this mass which is moving with 15 meter per second Moves up the hill when the motor stops. Okay, so motor is stopped. It has that velocity 15 meter per second motor is not Pushing it anymore. So if it is just able to reach the destination which is at a height 10 meter Above the point. We need to find work done Against the friction Fine, so work done against the friction will be what? Okay, so you can visualize the entire situation like this. So you have an inclined plane okay and There is Let's say this is the car Okay, this is the car that is moving With velocity of 15 meter per second Okay, so let's say it Goes to the destination here and stops Fine, so this destination is at a height of 10 meters Right, so this is situation. This is position one and this is position two. So if you apply work energy theorem Between position one and two you can say that w is u2 plus k2 minus u1 plus k1 now when you apply this theorem, this is like Work done by the friction on the car All right. So remember that So let's Put the values u2 is what there is only gravitation potential G. There is no spring out here So u2 is m which is 1400 G Let's take that as 10 mg into H Okay, k2 is what zero it stops after reaching there, right minus U1 is what you and I'm taking zero because from here. I am measuring the height Okay, so I'm taking gravitation potential initially to be zero Plus initial kinetic energy, which is half m that is 1400 into V square that is 15 square fine so this is The work done by the friction on the car, right and what is asked work done Against the friction so work done against a friction Will be negative of the work done which you have found right because what you have found is work done By the friction work done on the frictional force or work done against a friction force will be Negative of that. All right. So that's it for this particular question I hope you have learned something today in case you have any doubts, please feel free to get in touch with us Okay. Thank you