Question

A lead bullet of mass $0.1kg$, travelling with a velocity of $20m{s}^{-1}$, comes to rest after penetrating $20m$ in a still target. Find the average acceleration $\left(a\right)$ of the bullet.

Answer 1

Given:
Initial velocity, $u=20m{s}^{-1}$
Final velocity, $v=0$
Distance travelled, $s=20m$

From third equation of motion, we have
$v^2=u^2+2as$​
$0^2={20}^2+(2\times a\times 20)$
$\Rightarrow a=-10m{s}^{-2}$