Question

A bullet of mass 20 g is horizontally fired with a velocity 150 m/s from a pistol of mass 2kg. What is the recoil velocity of the pistol?

Answer 1

m1 = 20 g = 0.02 kg 
u1 = 150 m /s 
m2 = 2 kg
u2 = ? 

m1u1 = - m2u2 
0.02 x 150 =  - 2 x u2 
3 / -2          = u2 

-1.5 m/s = u2 

Answer 2

By using law of conservation of momentum recoil velocity is given as
v = mu / M
= (20 × 10^-3) × 150 / (2)
= 1.5 m/s

Recoil velocity of gun is 1.5 m/s