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. (a) and (b) both
• D. None of the above

Answer 1

The correct option is A

Brake sharply

When driver applies brakes and the cars covers distance $x$ before coming to rest, under the effect of retarding force $F$

then $\frac{1}{2}m{v}^2$ = $Fx$ $\Rightarrow$ $x$ = $\frac{m{v}^2}{2F}$

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 breaks. This retarding force is actually a friction force.