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Question
A train is moving with a velocity of 90 km h-1 . It is brought to stop by applying the brakes which produce a retardation of 0.5 ms-2 Find :
(i) The velocity after 10 s , and
(ii) the time taken by the train to come to rest .
Solution
Initial velocity u = 90 km/h = 25 m/s
Final velocity v = 0 m/s
Acceleration a = -0.5 m/s2
(i) Let 'V' be the velocity after time t = 10 s
Using the first equation of motion,
v = u + at
We get,
V = 25 + (-0.5) (10) m/s
V = 25 - 5 = 20 m/s-1
(ii) Let t' be the time taken by the train to come to rest.
Using the first equation of motion,
v = u + at
We get,
t' = [(0 - 25)/ (-0.5)] s
t' = 50 s
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