Question

A BULLET OF MASS 10gm MOVING WITH A VELOCITY OF 400m/s gets embedded in a freely suspended wooden block of mass 900gm . WHAT IS THE VELOCITY ACQUIRED BY THE BLOCK ?

Answer 1

Write the momentum conservation: initial momentum of the bullet equals the final momentum of the bullet and the block:

$$mv=u(M+m).$$

According to momentum conservation, the velocity of the block with the bullet embedded is

$$u=v\frac{m}{M+m}=4.4\text{ m/s}.$$