Question

A car of mass $\text{1000 kg}$ moving with a velocity of $\text{20 m/s}$ is brought to rest by applying brakes in $\text{10 seconds}$. What is the force applied by the brakes?

• A. $\text{1000 N}$
• B. $\text{2000 N}$
• C. $\text{4000 N}$
• D. $\text{10000 N}$

Answer 1

The correct option is B $\text{2000 N}$

Given, Mass of car, m = $1000kg$

Initially velocity, u = $20m/s$

Final velocity, v = $0$,

Time taken, t = $10s$

Let the acceleration be ‘a’ and the force applied be ‘F’.

We know,

$a=\frac{(v-u)}{t}$

$a=\frac{(0-20)}{10}=-2\frac{m}{s^2}$

$F=m\times a=1000\times -2=-$ $\text{2000 N}$

(Negative sign indicates that the force is acting in the opposite direction)

Therefore, force applied by the brakes $\text{= 2000 N}$