Question

A particle starts moving towards positive $x$-axis with initial velocity $4 \,m / s$. Acceleration of the particle is $2 \,m / s ^{2}$ towards negative $x$-axis. Find the distance (in $m$ ) travelled by the particle in $4\, s$.

Answer 1

$s=u t+\frac{1}{2} a t^{2} $
$v=u+a t $
$\Rightarrow v=u-2\, t$
At $t=2 \,s , v=0$
For $t=0$ to $t=2$,
particle moves along $+$ve $x$-direction and
for $t=2$ to $t=4$,
particle moves along $-$ve $x$-direction.

So, total distance travelled
$=\frac{2 \times(4)^{2}}{2 \times 2}=8\, m$