A 10 g bullet accelerates to 400 m/s after being fired from a gun with a mass of 2.0 kg.       (i) What is the momentum of the bullet? 

      (ii) What is the momentum of the gun?

     (iii) What is the velocity of the recoiling gun?

See the answers below.

Explanation:

Momentum is defined as the product of mass by velocity, and can be calculated by means of the following expression.

where:

P = Momentum [kg*m/s]

m = mass = 10 [g] = 0.01 [kg]

v = velocity = 400 [m/s]

i)

ii)

The momentum of the gun is equal to zero, because it does not move before being fired, the weapon only moves after having fired the weapon.

iii)

Since the momentum is conserved before and after the shot, the same momentum given to the bullet is equal to the momentum received by the gun.