Question

A car weighing $1000$ $kg$ and travelling at $30$ $m/s$ stops at a distance of $50$ $m$ decelerating uniformly. What is the force exerted on it by the brakes?

• A. $9500$ $N$
• B. $1800$ $N$
• C. $4500$ $N$
• D. $9000$ $N$

Answer 1

The correct option is D. $9000$ $N$

Mass of the car $\left(m\right)=1000$ $kg$

Initial velocity $\left(u\right)=30$ $m/s$

Distance travelled $\left(s\right)=50$ $m$

Since the car stops, final velocity $\left(v\right)=0$

As we know,

$v^2-u^2=2as$

$0-900=2(-a)\left(50\right)$ $;negativesignrepresentsretardation$

$a=9m/se{c}^2$

$\therefore F=ma$

$F=\left(1000\right)\left(9\right)=9000N$

The force exerted by the brakes is $9000$ $N.$