Question

A body of mass $2kg$ having a velocity of $2m{s}^{-1}$ is brought to rest within a distance of $2m$. Find the magnitude of force acting on the body.

• A. $8N$
• B. $1N$
• C. $4N$
• D. $2N$

Answer 1

The correct option is D $2N$

Given:
Initial velocity, $u=2m{s}^{-1}$
Stopping distance, $s=2m$
As the object comes to rest, final velocity $v=0m{s}^{-1}$
Mass, $m=2kg$

Let the acceleration be $a$
From the third equation of motion, we have
$v^2-u^2=2as$
$a=\frac{v^2-u^2}{2s}=\frac{0^2-2^2}{2\times 2}=-1m{s}^{-2}$

From Newton's second law of motion, force on the body is:
$F=m\times a$
$F=2\times -1=-2N$

It may be noted that the negative sign implies that the force is acting in a direction opposite to the motion of the object.