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A driver takes 0.20 s to apply the brake...

A driver takes 0.20 s to apply the brakes after he sees a need for it. This is called the reaction time of the driver. If he is driving a car at a speed of `54 km//h` and the breakes cause a deceleration of `6.0 m//s^(2)`, find the distnce travelled by the car after he sees the need to put the brakes on?

Text Solution

Verified by Experts

In reactiion time the body moves with the speed of 54 km/hr = 15m/sec (constant speed).
Distance travelled in this time,
`S_1=15xx0.2
=3m
When breades are applied
u=15 m/s
v=0
a=-6m/s^2(deceleration)
S_2=(v^2-u^2)/(2a)
=(0-15^2)/(2(-6))
=18.75m
Total distance = S_1+S_2
=3-18.75+21.75m
= 22m`.
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