Question

A bullet fired into a target loses half of its velocity after penetrating $15cm$. How much further will it penetrate before coming to rest?

• A. $5cm$
• B. $25cm$
• C. $8.3cm$
• D. $75cm$

Answer 1

The correct option is A $5cm$

Applying the Equation of motion for the initial velocity of the bullet

$v^2=u^2+2aS$

$a=-\frac{u^2}{40}$

Applying the equation of motion for the bullet after penetrating 15cm

$v^2=u^2+2aS$

Here, $u=0$ where the bullet is at the rest

The initial velocity of the bullet after penetrating 15cm is $\frac{u}{2}$

Applying the data in the equation of motion

We get

$v^2=u^2+2aS$

$\Rightarrow \frac{u^2}{20}S=\frac{u^2}{4}$

$\Rightarrow S=5cm$