Question

If a car at rest accelerates uniformly and attains a speed of $72 \,km/h$ in $10 \,s$, then it covers a distance of

• A. 50 m
• B. 100 m
• C. 200 m
• D. 400 m

Answer 1

Answer: (B)

100 m

Answer 2

From equation of motion
$v=u+a t$
where $v$ is final velocity, $u$ the initial velocity, $a$ the acceleration and $t$ the time.
Given, $u =0,$
$v =72 \,km / h$
$=72 \times \frac{5}{18}=20\, m / s$
$t =10 \,s$
$\therefore 20 =0+a \times 10$
$\Rightarrow a =\frac{20}{10}=2\, ms ^{-2}$
From second equation of motion
$s=u t+\frac{1}{2} a t^{2}$
$s=0+\frac{1}{2} \times 2 \times(10)^{2}$
$=100 \,m$