Question

A car moving at a speed of 30 kilo meters per hour is brought to a halt in 8 metres by applying brakes. If the same car is moving at 60 km. per hour, it can be brought to a halt with same breaking power in

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

Answer 1

The correct option is D 32 metres

$From{v}^2=u^2-2as0=u^2-2ass=\frac{u^2}{2a}\Rightarrow s\alpha u^2(ifa=constant)\frac{s_2}{s_1}={\left(\frac{u_2}{u_1}\right)}^2={\left(\frac{60}{30}\right)}^2=4\Rightarrow s_2=4s_1=4\times 8=32metres$.