Question

A bus running at a speed of $18km/h$ is stopped in $2.5$ seconds by applying brakes. Calculate the retardation produced.

Answer 1

Initial velocity, $u=18km/h$
$u=18\times \frac{1000}{3600}=\frac{18000}{3600}m/s=5m/s$

Final velocity, $v=0m/s$
Time, $t=2.5sec$
Acceleration, $a=?$

Using, $v=u+at$

$a=\frac{v-u}{t}=\frac{0.5}{2.5}=-2m/s^2$

So, retardation is $2m/s^2$..