Question

A person driving a car with a speed 72 km hr suddenly sees a boy crossing the road . if the distance move by car ,before the person applies brakes is 5m ,what is the reaction time of the person

Answer 1

Given ,speed is equal to 72km/h
First of all convert speed into m/s ,we get; Speed = 20 m/s
And d = 5m
Therefore ,t =d/s
=5/20
=1/4=0.25

Thus; t=0.25 seconds

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.