Question

What happens when a bullet is fired from a rifle?

(a) The rifle becomes weightless

(b) We fall back

(c) Rifle gives backward kick

(d) Bullet doesn’t leave the rifle

I got this question by my college professor while I was bunking the class.

My question is taken from Dimensional Analysis topic in portion Advanced Engineering Materials of Engineering Physics II

Answer 1

Right choice is (c) Rifle gives backward kick

For explanation: A rifle gives a backward kick on firing a bullet. Before firing, both the bullet and rifle are at rest and the initial momentum of the system is zero. As soon as the bullet is fired, it moves forward with a large velocity. In order to conserve momentum, the rifle moves backward with such a velocity that the final momentum of the system is zero.