A person driving a car at a speed 72 km per hour, sees a boy crossing the road. If the distance moved by the car before the person applies brakes is 5 m, find the reaction time of the person.

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Solution

Velocity of the car, $v = 72 k m / h r = 72 \times \frac{5}{18} m / s = 20 m / s$
Distance moved by the car $= 5 m$
So, reaction time, $t = \frac{D i s t a n c e m o v e d b y t h e c a r}{V e l o c i t y o f t h e c a r}$
$= \frac{5}{20} = \frac{1}{4} = 0.25 s$

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A person driving a car at a speed 72 km per hour, sees a boy crossing the road. If the distance moved by the car before the person applies brakes is 5 m, find the reaction time of the person.

Velocity of the car, v=72 km/hr=72×518 m/s=20 m/s Distance moved by the car =5 m So, reaction time, t=Distance moved by the carVelocity of the car =520=14=0.25 s

Velocity of the car, $v = 72 k m / h r = 72 \times \frac{5}{18} m / s = 20 m / s$
Distance moved by the car $= 5 m$
So, reaction time, $t = \frac{D i s t a n c e m o v e d b y t h e c a r}{V e l o c i t y o f t h e c a r}$
$= \frac{5}{20} = \frac{1}{4} = 0.25 s$