Question

A bullet of mass 0.02 kg is fired from a gun weighing 7.5kg .if the initial velocity of the bullet is 200 m/s, calculate the speed with which the gun recoils.

Answer 1

According to Law of Conservation of ,momentum :
Mass of bullet x velocity of bullet = Mass of gun x recoil velocity of gun
0.02 x 200 = 7.5 x recoil of gun
Recoil of gun = 0.02 x 200/7.5
                      = 0.53 m/s

Answer 2

Given:

Mass of bullet,m=0.02 kg

Mass of gun,M=7.5 kg

Speed of bullet,v=200 m/s

To find:

Speed with which the gun recoils

Solution:

Using law of conservation of momentum

$mv=MV$

Substitute the values

$0.02\times 200=7.5V$

$V=\frac{0.02\times 200}{7.5}$

$V=\frac{4}{7.5}=0.53 m/s$

Hence, speed of gun =0.53 m/s