Question

An automobile travelling with a speed of 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

(a) 20 m 

(b) 40 m

(c) 60 m 

(d) 80 m.

Answer 1

(d) : Let a be the retardation for both the vehicles
For automobile, v ² = u ² – 2 as

Similarly for car, u₂² = 2as ₂