An automobile travelling with a speed `60 km//h` , can brake to stop within a distance of `20 m` . If the car is going twice as fast i. e. , `120 km//h`, the stopping distance will be

Options

A. 60 m
B. 40 m
C. 20 m
D. 80m

Answer

D

Explanation

Assuming constant retardation:
using ` v^(2) =u^(2) +2as rArr 0=u^(2) -2as ` or ` s=(u^(2))/(2a) or (S_1)/(s_2) =(u_1^(2))/(u_2^(2)) , " " (20 )/(s_1) ((60)/(120))^(2) rArr " "s_2 =80m`