Question

An express train going towards Delhi is travelling at a speed of $90kmph$. Brakes are applied so as to produce a uniform acceleration of $–0.5m{s}^{-2}$ . Find how far the train will go before it is brought to rest.

• A. $600m$
• B. $725m$
• C. $625m$
• D. $500m$

Answer 1

The correct option is C

$625m$

Given,
initial velocity, $u=90kmph$ = $90\times \frac{5}{18}$ $=25m{s}^{-1}$
acceleration, $a=–0.5m{s}^{-2}$
final velocity, $v=0$ (brakes are applied)
Let 's' be the distance travelled.
From the third equation of motion,
$v^2=u^2+2as$

$0={25}^2+(2\times -0.5\times s)$

$\Rightarrow s=625m$

Hence the distance covered is $625m$.