Question

A gun of mass 20kg fires a bullet of mass 100kg with speed of 100m/s. What will be the recoil velocity of the gun?​

Answer 1

Answer:

50 m/s

Explanation:

Law of conservation of momentum

mv = constant

m1v1 = m2v2

Answer 2

Momentum of system before Firing..

mass of gun, M = 20 kg

mass of bullet, m = 100 kg

velocity of gun, U = 0 m/s

velocity of bullet, u = 0 m/s { because the bullet has not been fired }

∴ Momentum of system = MU + mv

==> 20×0 + 100×0

==> 0 kg.m/s

Momentum of System after firing..

mass of gun, M = 20 kg

mass of bullet, m = 100 kg

velocity of gun, V = x m/s { we dont know the recoil velocity, so take it as x }

velocity of bullet, v = 100 m/s

∴ Momentum of system = 20×x + 100×100

==> 10000 + 20x

Here,

Momentum of System before firing = Momentum of system after firing { Law of conservation of momentum }

==> 0 = 10000 + 20x

==> 20x = -10000

==> x = -10000/20

==> x = -500 m/s

Hence, The recoil velocity of the gun is -500 m/s