Question

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^-1, what is the recoil speed of the gun?

Answer 1

m₁ = 0.02 kg, m₂ = 100 kg

v₁ = 80 m/s v₂ = ?

According law of conservation of momentum

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

0.02 (0) + 100 (0) = 0.02 × 80 + 100 × v₂

v₂ = – 1.6 × 10^-2 m/s.