a person driving a car with a speed 72km/h, suddenly sees aboy crossing the road. if the distance moved by a car,before the person applies brakes is 5m,the reaction time for the person is
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initial velocity = 72 Km/ h = 20 m/s
final velocity = 0 ( because brakes are applied)
distance covered before applying g the brakes = 5 m
v = u + at
v= 0 + at
a= v/t
now, v^2 = u^2 + 2aS
(20)^2 = 0 + 2( v/t)S
400 = 2(20/t) 5
t = 2*20*5/400
=200/400
t= 0.5 sec.
final velocity = 0 ( because brakes are applied)
distance covered before applying g the brakes = 5 m
v = u + at
v= 0 + at
a= v/t
now, v^2 = u^2 + 2aS
(20)^2 = 0 + 2( v/t)S
400 = 2(20/t) 5
t = 2*20*5/400
=200/400
t= 0.5 sec.
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