Rankers Physics
Topic: Kinematics
Subtopic: Equations of Motion

A person driving a car with a speed 54 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
0.5 sec
0.66 sec
0.33 sec
1 sec

Solution:

Using time=svt = \frac{s}{v}, with v=54v = 54 km/h = 15 m/s and s=5s = 5 m:

t=515=0.33 st = \frac{5}{15} = 0.33 \text{ s}

Reaction time = 0.33 s.

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