Question

A driver driving a truck at a constant speed of 20 ms -1 suddenly saw a parked car ahead of him by
95 m. He could apply the brake after some time to produce retardation of 2.5 ms? An accident
was just avoided, his reaction time is :
(A) 0.5 s
(B) 0.75 s
(C) 0.85
(D) 1 s​

Answer 1

Answer:

(B) 0.75 s

Explanation:

The distance covered by the truck to stop with constant retardation of 2.5m/s^2 is 80m.

Distance between car and truck is 95m.

Means, The driver applies the brakes after reaching 15 m away from the point at which he saw the car, so during the first 15 m of his journey his speed will be constant i.e. 20m/s and we have to calculate the reaction time which is the time taken in travelling the first 15m and time taken is displacement/velocity, here displacement is 15m and velocity is 20m/s.

So, Time taken = 15/20 = 0.75s

Hope it helps (:

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