 So, after find location what is the next thing that we study in telematics the movement of the body that is what velocity right. So, let us try to understand how to quantify the velocity of the system now ok. Please write down take off the rate at which the location of central mass is changing is the velocity of central mass is the velocity of central mass. So, suppose I have to make sure that all of this thing what is central mass what is this all of it will be quiet. So, if there is someone who is making you write so much probability you have made a lot of noise in your school is there something chance go on ok. So, you might not make noise only in physics you are making noise. Alright, so our central mass we have got it as m1 r1 the position vector of the central mass. So, rate at plus m2 into dI2 by dt you are fine see this you can write as this will give me m1 v1 plus m2 v2 divided by see here we have assumed something what is the assumption point masses their point masses ok. And even if they are not if it rotates while moving every point will have different velocity point masses if they are not and what you should do you should find out the values masses just like location of central mass v o cm will be m1 into plus m2 into velocity of central mass of 2 divided velocities. Whole mass if it moves the same velocity mass that is all point of the same velocity. All of you missed a small portion in location of central mass. So, when you edit this video put this ahead of we see. So, let us take couple of question of mass it is a square the radius this is like this semi-circular this semi-circular ring semi-ring same it is ok. Mass is uniformly distributed with mass per unit area is sigma find out the central mass location. See simply m2 m1 into central mass of the this is follow hemisphere. Simply formula you have to apply choose your x y i not having to play with direct sigma into a sigma into y is 0 comma 0 x c m to is what? The central mass will be somewhere here the resistance this resistance r by 2 so r by 2 plus 2 r plus r so 3 r we have to substitute they can do that at home. Now tell me y c m1 y c m2 and y c m3 these values you tell me this is 0 y c m2 is 0 y c m3 minus r you can substitute the answer ok. So, you can get fine don't substitute and start finding answer all right you can do it at home have you understood ok. Now one more question then we go to the loss of central mass I am giving you simple ok focus here small sphere is taken out from the bigger scale you know now do it 4 by 3 how much is this? How much? How much? How much? How much? How much? How much? How much? How much? I can say the central mass of this is 0 comma 0 mass of this which is m into central mass plus mass of this into central mass of height which is 8 m by 7. Now just finding the central mass itself that's it will be at least 50 to 60 questions of this topic itself. this topic itself. So of course you can't solve particles. Now velocity 1 or 2 questions will be there. Two components of each velocity. Similar to the center of mass definition. Very similar to that. Yes or no? Okay. In this case I don't need to know where is the coordinate axis. The direction is x axis.