Question:
A bullet of mass $0.1 \mathrm{~kg}$ is fired on a wooden block to pierce through it, but it stops after moving a distance of $50 \mathrm{~cm}$ into it. If the velocity of bullet before hitting the wood is 10 $\mathrm{m} / \mathrm{s}$ and it slows down with uniform deceleration, then the magnitude of effective retarding force on the bullet is ' $x$ ' $N$. The value of ' $x$ ' to the nearest integer is________.
Solution:
$\mathrm{v}^{2}=\mathrm{u}^{2}+2 \mathrm{as}$
$0=(10)^{2}+2(-a)\left(\frac{1}{2}\right)$
$a=100 \mathrm{~m} / \mathrm{s}^{2}$
$\mathrm{F}=\mathrm{ma}=(0.1)(100)=10 \mathrm{~N}$