Question

A car traveling at a speed $30km{h}^{-1}$ is brought to a halt in 8 m by applying breaks. If the same car is traveling at $60km{h}^{-1}$, it can be brought to a halt with the same breaking power in :

• A. 32 m
• B. 24 m
• C. 16 m
• D. 8 m

Answer 1

The correct option is A 32 m

Applying kinetic energy theorem

$\Delta KE=\Delta w$

$\frac{1}{2}m{v}^2=F\bullet s$

$v^2\propto s$

$\frac{v_1^2}{v_2^2}=\frac{s_1}{S_2}$

$v_2=2v_1$

= $\frac{1}{4}=\frac{s_1}{s_2}$

$s_2=4s_1$

$=4\times 8$

= 32

Hence (A) option is correct answer