A body of mass m1 = 4 kg moves at 5i^ ms-1 and another body of mass m2 = 2 kg moves at 10i^ ms-1. The kinetic energy of centre of mass is

Velocity of centre of mass,          vCM=m1dr1dt+m2dr2dtm1+m2=4×5i^+2×10i^4+2=40i^6=203i^The kinetic energy of centre of mass,          K=12mvCM2=12×(4+2)×20×203×3              =12×6×20×203×3=4003 J