A moving particle of mass m, makes a head on elastic collision with another particle of mass 2m, which is initially at rest. The percentage loss in energy of the colliding particle on collision, is close to

Conservation of total kinetic energy of the system during collision  12m1u12+12m2u22=12m1v12+12m2v22 or v1=m1−m2m1+m2u1+2m2u2m1+m2 put m1=mm2=2mu2=0 ⇒v1=−u13  Initial kinetic energy of the colliding body is given by,  (K.E)i=12mu12 (K.E)f=12m−u132 ΔK.E=(K.E)i−(K.E)f %ΔK.E(K.E)i=89×100=89%≈90%