Example:

Suppose a bullet of mass m strikes a block of mass M resting on a horizontal smooth floor and gets embeded into it. If the velocity of the bullet is V, find out the velocity of the(block+bullet) after the bullet has embeded into it.

Solution:

Applying the principle of momentum,

mV=(M+m)V_f

where V_f is the final velocity.

Thus,

Now let us calculate the kinetic energy of the system before and after the impact.