A car moving along a straight highway with speed of 126 km/h is brought to a stop within a distance of 200 m. What is the retardation of the car (assumed uniform), and how long does it take for the car to stop?
Given,
Initial velocity of the car, u = 126 km/h
= 
= 35 m/s
Distance covered before stop, s = 200 m
Final velocity of the car, v = 0 m/s
Let, the retardation be ‘a’.
From the 3rd equation of motion,
v2 – u2 = 2as
where,
v = Final velocity
u = Initial velocity
a = Acceleration / Deceleration
s = Distance covered
∴ a = 
= 
ms-2 = -3.06 ms-2
From the 1st equation of motion,
v = u + at
where,
v = Final velocity
u = Initial velocity
a = Acceleration
t = Time
∴ t = 
= 
s = 11.44 s
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