Question

A bullet of mass$0.1kg$ is fired on a wooden block to pierce through it, but it stops after moving a distance of $50cm$ into it. If the velocity of the bullet before hitting the wood is $10m/s$ 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

Answer 1

Step 1: Given data and drawing the diagram for given situation

Mass of bullet, $m=0.1kg$

Distance covered, $s=50cm=0.5m$

Velocity of bullet, $u=10m/s$

Step 2: Find retardation, $a$

Applying $3^{rd}$ equation of motion,

$$\begin{gathered} v^2=u^2+2as \\ 0={10}^2+2(-a)\times 0.5 \\ a=100m/s^2 \end{gathered}$$

Step 3: Find retardation force, $F$

$$\begin{gathered} F=ma \\ F=0.1kg\times 100m{s}^{-2} \\ F=10N \end{gathered}$$

Thus, the retardation force is $10N$.