A moving particle of mass 'm' makes head on elastic collision with a particle of mass '2m' which is initialy at rest. The fraction of K.E. lost by colliding particle is

fractional loss KE is Alternative Method:m x v1 + 2m x v2 = m x u1 + 2m x 0⇒ v1 + 2v2 = u1..........(1)Also, ⇒ v2 - v1 = u1.........(2)solving, v1 = -u1/3 Fraction of KE lost by m1