Question

A car is moving with a speed of $50kmh^{- 1}$ , can be stopped by brakes after at least $6m$ . If the same car is moving at a speed of $100kmh^{- 1}$ the minimum stopping distance is :-

• A. $12m$
• B. $18m$
• C. $24m$
• D. $6m$

Answer 1

Answer: (C)

Stopping distance $s=\frac{u^{2}}{2 a}$
$s \propto u^{2}$ (car is same)
$\frac{s_{1}}{ s_{2}}=\frac{u_{1}^{2}}{u_{2}^{2}}\Rightarrow \frac{6}{ s_{2}}=\left(\frac{50}{100}\right)^{2}=\left(\frac{1}{2}\right)^{2}=\frac{1}{4}$
$S_{2}=6\times 4=24$