Question

A car of mass 2400 kg moving with a velocity of 20 ms⁻¹ is stopped in 10 seconds on applying brakes. Calculate the retardation and the retarding force.

Answer 1

The initial velocity of the car = 20 ms⁻¹

The final velocity of the car = 0

Time taken by the car to stop = 10 s

Using the first equation of motion, we can write, $v=u+at$

So,
$0=20+a\times 10$

$\Rightarrow a=-2{\mathrm{ms}}^{-2}$

Hence, retardation is 2 ms^-2.

Retarding force = mass $\times$ retarding acceleration
= 2400 kg $\times$ 2 ms^-2
= 4800 kg ms^-2
= 4800 N