Question

A car at rest has mass $1000kg.$ It is moved by a horizontal force of $50N$ over a horizontal surface. Calculate the work done by the force in $8s$.

Answer 1

If $a$ be the acceleration of the car,

Then by Newton's second law of motion

$F=ma$

$\Rightarrow a=\frac{F}{m}=\frac{50}{1000}=0.05m/s^2$

By second equation of motion,

$S=ut+\frac{1}{2}a{t}^2$

Given:

Time $t=8s$

Initial velocity $u=0$

The displacement in $8s$ is

$S=0\left(8\right)+\frac{1}{2}\left(0.05\right)(8{)}^2=1.6m$

Work done by the force in $8s$ is,

$W=F\times S=\left(50N\right)\times \left(1.6m\right)=80J$