Question

a bullet of mass m penetrates a thickness h of a stationary block of mass M which is restricted to move , if block is free to move, how much will the bullet penetrate?

Answer 1

Assuming retardation force F to same in both cases, we have ,Retardation a = F/mUsing v^2 = u^2 -2as, we have ,0=u^2 -2(F/m)hSo , F =mu^2/2h