Question

A car starts from rest and accelerates uniformly to a speed of $90\text{km/h}$ in $5\text{s}$. The distance covered by the car in this time interval is

• A. $125\text{m}$
• B. $60\text{m}$
• C. $62.5\text{m}$
• D. $48\text{m}$

Answer 1

The correct option is C $62.5\text{m}$

Given Final Speed, $v=90{\text{kmh}}^{-1}=25{\text{ms}}^{-1}$
Time taken $t=5\text{s}$
Using first equation of motion, $v=u+at$
$\therefore$ Acceleration of the car $a=\frac{v-u}{t}=\frac{25-0}{5}$($u=0$ as body starts from rest)
$=5{\text{ms}}^{-2}$
Thus, the distance covered by the car
$S=ut+\frac{1}{2}a{t}^2$ (Using second equation of motion)
$S=0+\frac{1}{2}\times 5\times (5{)}^2$
($u=0$ as body starts from rest)
$S=62.5\text{m}$