Question

Brakes are applied by a truck to produce retardation of $10m{s}^{-2}$. If the truck takes 5 seconds to stop after applying the brakes, the distance covered by the truck before coming to rest is

• A. 125 m
• B. 150 m
• C. 175 m
• D. 200 m

Answer 1

The correct option is A

125 m

Here, final velocity of truck = v, acceleration of truck = a, time taken by by truck to stop = t and s = distance covered by the truck before coming to rest
Given,
$v=0m{s}^{-1}$ , $a=-10m{s}^{-2}$ ​ , t = 5 s
Let 'u' be the initial velocity.
From first equation of motion, $v=u+at$,
$0=u+(-10\times 5)$
$\Rightarrow u=50m{s}^{-1}$
Also, from third equation of motion, $v^2$ = $u^2+2as$
$\Rightarrow 0={50}^2+2\times (-10)\times s$
$\Rightarrow s=125m$
Therefore, the truck will stop after $125m$.