Question

A car moving with a speed of $50 \, km \, h^{- 1}$ can be stopped by brakes in at least $6 \, m$ . If the same car is moving at a speed of $100 \, km \, h^{- 1}$ , then the minimum stopping distance (in $m$ ) is

Answer 1

The stopping distance of a car is
$s=\frac{u^{2}}{2 a}$
Therefore, for the two situations given in the question, we can write
$\frac{s_{1}}{s_{2}}=\left(\frac{u_{1}}{u_{2}}\right)^{2}=\frac{1}{4}$
$\frac{6}{s_{2}}=\frac{1}{4}\Rightarrow s_{2}=24 \, m$