Question

a bullet ofass 0.012 kg and horizontal speed 70 m/s strikes a block of wood of mass 0.4 kg and instantly comes to rest with respect to the block. The block is suspended from ceiling by means of thin wires. Calculate the height to which the block rise.

Answer 1

by momentum consevation
0.012*70=(0.4+0.012)*v
v=2 m/s approx
by v^2=2gh
4=2*10*h
h=0.2 m