Question

A bullet is fired on a wall with velocity 100ms^-1. If the bullet stops at a depth of 10cm inside the wall, find the retardation produced by the wall.

Answer 1

Step 1:Given data:

$s=10cm=0.1m$

$u=100m{s}^{-1}$

$v=0m{s}^{-1}$

Step 2: Formula used

Acceleration (or retardation in this case) is defined as the rate of change in velocity.

Also, from the third equation of motion,

We know that,

$v^2-u^2=2as$

Here,

v is the final velocity of the bullet

u is the initial velocity of the bullet

a is the constant acceleration or retardation

s is the distance

Step 3: Finding the retardation produced by the wall:

Using the third equation of motion,

$$\begin{gathered} v^2-u^2=2as \\ 0-{100}^2=2a\times 0.1 \\ 2a=-\frac{10000}{0.1} \\ a=\frac{-100000}{2} \\ a=-5\times {10}^{4}m{s}^{-2} \end{gathered}$$

Hence, the retardation is $-5\times {10}^{4}m/s^2$.