Question

25. A person driving a car with a speed 72 km/h, suddenly sees a boy crossing the road. If the distance moved
by car, before the person applies brakes is 5 m, the reaction time of the person is
(1) 0.58
tacts)
(2) 0.10 s
(3) 10s
(4) 0.25 s​

Answer 1

Answer:

4) 0.25s

Formula:

Distance =:velocity × Time .

Time = Distance / Velocity

The reaction time will be given by the speed and the distance covered .

72 km/hr = 72000m /60 × 60s = 20m/s

Speed = 20 m/s

if 20 metre is covered in 1 × 5/ 20 = o.255

Therefore his reaction time is 0.25 second .

Thanks .

Answer 2

Answer:

Explanation:

Given :-

Initial velocity of a car, u = 72 km/h = 5/18 × 72 = 20 m/s

Distance covered by car , t = 5 meter

To Find :-

Reaction Time taken by car = ?

Formula to be used :-

Distance = Velocity × Time

Time = Distance/Velocity

Solution :-

Putting all values, we get

Time = Distance/Velocity

Time = (5/20) seconds

Time = (1/4) seconds

Time = 0.25 seconds.

Hence, the reaction time of the person is  0.25 seconds.