In this video, we are discussing Irodov problem- . we will learn how we can solve collision problem easily in CM frame. in CM frame Kinetic enegry wiil be= 0.5(m1u1c)^2+ 0.5(m2u2c)^2+ 0.5(m1 +M2)Vc)^2. beacuse the third term is const so change in K.E is same as in Lab frame.