Question

A bullet of mass 60g is fired from gun of mass 10kg with a velocity of 60m/s .Calculate the velocity of recoil of the gun .

by using : MV= -mv

Answer 1

-0.06*60 = 10 v
v=-0.36 m/s

Answer 2

mass of bullet = 60 g = 0.06 kg 
mass of gun = 10 kg 
velocity of bullet = 60 m/s
u of bullet = 0
u of gun = 0 
Therefore,

m₁u₁ +m₂u₂ = m₁v₁ + m₂v₂
0.06 * 0 + 10 * 0 = 0.06 * 60 m/s + 10v
0 = 3.6 + 10v
-3.6 = 10 v
v = -3.6 / 10 = - 0.36 m/s

Hence the recoil velocity of the gun is 0.36 m/s