Q 11-02-022NEETJEE MainTop questionEasy
A car moving at $54$ km/h can be stopped by its brakes in a distance of $15$ m. With the same braking retardation, the minimum stopping distance when it moves at $72$ km/h is
Answer: (C) $26.7$ m
Concept. With the same retardation, $s = \dfrac{u^2}{2a} \propto u^2$.
Step 1. Ratio.
$$\frac{s_2}{s_1} = \left(\frac{72}{54}\right)^2 = \frac{16}{9}$$
Step 2. Distance. $s_2 = 15 \times \dfrac{16}{9} = 26.7$ m.
Answer. $26.7$ m (Option C).
Solution by Sreeraj P, M.Sc Physics