Question

A lead bullet of mass 2 kg, travelling with a velocity of$20\frac{m}{s}$, comes to rest after penetrating 20 m in a still target. Find the resistive force applied by the target and acceleration of the bullet.

• A. Acceleration = 20 m/s² and F = -40 N
• B. Acceleration = 40 m/s² and F = +80 N
• C. Acceleration = 40 m/s² and F = -80 N
• D. Acceleration and force are 0

Answer 1

The correct option is C

Acceleration = 40 m/s² and F = -80 N

We know that, $v^2=u^2+2as$​

$v=0\frac{m}{s}$

$u=20\frac{m}{s},s=20m$
So, $0={20}^2+2\times a\times 20$

Acceleration = $-10m/s^2$

So, $F=ma=2\times -10$

$F=-20N$