Ncert Exercises & Solutions

Question 5.19:

A shell of mass 0.020 kg is fired by a gun of mass 100 kg. If the muzzle speed of the shell is 80 m/s, what is the recoil speed of the gun?

Mass of the gun, M= 100 kg

Mass of the shell, m= 0.020 kg

Muzzle speed of the shell, v = 80 m/s

Recoil speed of the gun = V

Both the gun and the shell are at rest initially.

The initial momentum of the system = 0

Final momentum of the system = mv - MV

(The negative sign shows that the directions of the shell and the gun are opposite to each other.

According to the law of conservation of momentum:

Final momentum = Initial momentum

mv - MV= 0

Or, V = mv / M

= 0.020 x 80 / 100 x 1000

= 0.016 m/s

Question 5.20: