Question

A body of mass $36kg$ is travelling with a speed of $12m{s}^{-1}$. What is the magnitude of force required to reduce the speed of the car to $4m{s}^{-1}$ in $6s$?

• A. $40N$
• B. $44N$
• C. $48N$
• D. $52N$

Answer 1

The correct option is C $48N$

Given: mass of object $m=36kg$, time, $t=6s$, final velocity, $v=4m{s}^{-1}$ and inital velocity $u=12m{s}^{-1}$.
Let the acceleration of the body be $a$ and the magnitude of force be $F$.

Using the first equation of motion.
$v=u+at\Rightarrow a=\frac{v-u}{t}=\frac{4-12}{6}==1.34m{s}^{-2}$

Using Newton's second law,
$F=ma=36\times 1.34=48N$
Thus, the magnitude of force is $48N$