Question

A rifle of mass 2 kg is suspended by strings. The rifle fires a bullet of mass 0.01 kg at a speed of 200 m/s. The recoil velocity of the rifle is about ____.
(A) 0.001 m/s.
(B) 0.01 m/s.
(C) 0.1 m/s.
(D) 1 m/s

Answer 1

Answer:

option D  

Explanation:

given,

mass of the rifle,M = 2 Kg

mass of the bullet , m = 0.01 Kg

speed of the bullet, v = 200 m/s

recoil velocity ,v'= ?

initial velocity of bullet and rifle is zero.

using conservation of energy

Mu + m u' = M v'+ m v

0 + 0  = 2 x v' + 0.01 x 200

2 v' = -2

   v' = -1 m/s

negative sign represent the velocity of rifle is in opposite direction of bullet.

hence, the correct answer is option D