Question

The driver of a car travelling at velocity $v$ suddenly see a broad wall in front of him at a distance $d$. He should :

• A. Brake sharply
• B. Turn sharply
• C. Both (a) and (b)
• D. None of these

Answer 1

The correct option is A Brake sharply

When driver applies brakes and the car covers distance $x$ before coming to rest, under the effect of retarding force $F$.
Then $\frac{1}{2}m{v}^2=Fx$
or $x=\frac{m{v}^2}{2F}$
But when he takes turn, then
$\frac{m{v}^2}{r}=F$
$\Rightarrow r=\frac{m{v}^2}{F}$
It is clear that $x=\frac{r}{2}$
i.e., by the same retarding force the car can be stopped in a less distance if the driver apply brakes. This retarding force is actually a friction force.