Question

a car is moving along a straight highway with 126 km/hr speed is brought to rest in 200 m. What is the uniform retardation of the car and how long does it take for the car to stop.

Answer 1

V^2=U^2 - 2as
a = 3.0625m/sec^2
v = u - at
t = 11.437 second

Answer 2

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Answer:

Initial velocity of the car, u = 126 km/h = 35 m/s

Final velocity of the car, v = 0

Distance covered by the car before coming to rest, s = 200 m

Retardation produced in the car = a

From third equation of motion, a can be calculated as:

v2 - u2 = 2as

(0)2 - (35)2 = 2 × a × 200

a = - 35 × 35 / 2 × 200 = - 3.06 ms-2

From first equation of motion, time (t) taken by the car to stop can be obtained as:

v = u + at

t = (v - u) / a = (- 35) / (-3.06) = 11.44 s