Question

A bullet of mass 10g is shot from a gun of mass 5 kg with a velocity 400m/s.calculate the recoil velocity of the gun

Answer 1

(400x0.01)kg m/s=5xv
=>(400x0.01)/5=v
=>v=0.8m/s
I solved it by law of conservation of momentum

Answer 2

initial momentum of bullet = 0.01kg * 0m/s
final momentum of bullet= 10g *400m/s
=0•01kg * 400m/s
=4kgm/s
initial momentum of gun= 5kg * 0m/s
final momentum of gun = 5kg * v = 5vkgm/s
according to conservation of momentum
0 + 0 =4kgm/s + 5vkgm/s
v= 4/5 = -0.8
hence recoil velocity of the gun = 0.8m/s