A bullet of mass 20 gm is fired from a rifle of mass 20 kg with a muzzle velocity of 200 m/s. Find the velocity of the recoil of the rifle.

A bullet of mass 20 gm is fired from a rifle of mass 20 kg with a muzzle velocity of 200 m/s. 

The velocity of the recoil of the rifle is 0.2 m/s. 

By the law of conservation of momentum,

Initial momentum $=$ final momentum

$\therefore P_1=P_2$

$\therefore m_1{v}_1=m_2{v}_2$

here, $m_1=20gm ; v_1=200m{s}^{-1}$

$m_2=20kg=20,000gm$

$\therefore v_2={\displaystyle \frac{m_1{v}_1}{m_2}}$

$={\displaystyle \frac{20\times 200}{20,000}}$

∴$v_2$=0.2m/s