Question

A body of mass m hits normally a rigid wall with velocity v and bounces back with the same velocity. The impulse experienced by the body is

• A. $1.5mv$
• B. $2mv$
• C. zero
• D. $1mv$

Answer 1

The correct option is B

$2mv$

Step1: Impulse

1. When a large amount of force is exerted on a body in a very small time, then the force is called impulse.
2. Impulse is defined as the change in momentum in a small-time, i.e, impulse, $∆p=p_f-p_i$.

Step2: Finding the impulse

The momentum of the body, when it hits the wall is

$p_i=+mv$

The momentum of the body, when it is bounced back is

$p_f=-mv$

Now change in momentum,

$∆p=-mv-mv$

or $∆p=-2mv$

The impulse experienced by the body is $\mathbf{∆}\mathit{p}\mathbf{=}\mathbf{-}\mathbf{2}\mathit{m}\mathit{v}$. So Option (B) is correct.