Question

If a bus starts from rest, moving along a straight line and travelling with an acceleration of $8m{s}^{-2}$, then the displacement in the $thirdsecond$ is
_________ $m$.

• A. $3.1$
• B. $0.32$
• C. $20$
• D. None

Answer 1

The correct option is C

$20$

Step 1: Given Data,

Initial velocity $u=0m{s}^{-1}$

Acceleration $=8m{s}^{-2}$.

We need to find displacement in $3rd$ $second$.

Step 2: Calculation

Displacement at $nth$$second$is given by

$S_n=$$u+\frac{a}{2}(2n-1)$.

Where $u$ is initial velocity, $a$ is acceleration, $n$ is time and S is displacement.

So,

$S=0+$ $\frac{8}{2}(2\times 3-1)$

$S=4\times 5=20m$

Hence the displacement in the $3rdsecond$ is $20m$.

So the correct option is (C) $20m$.