Question

Brakes are applied to a truck to produce an acceleration of $–10m{s}^{-2}$​. If the truck takes $5s$ to stop after applying the brakes, then find the distance covered by the truck before coming to rest.

• A. $250m$
• B. $125m$
• C. $-125m$
• D. $-250m$

Answer 1

The correct option is B $125m$

Given, final velocity, $v=0$, acceleration, $a=-10m{s}^{-2}$, time taken, $t=5s$.
Let the initial velocity be $u$.
From the first equation of motion, $v=u+at$,
$0=u+(-10\times 5)$
$\Rightarrow u=50m{s}^{-1}$
From third equation of motion, $v^2$ = $u^2+2as$,
$0={50}^2+2\times -10\times s$
$\Rightarrow s=125m$
Therefore, the truck will stop after $125m$.