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Question
A train moving with a velocity of 20 m s-1 is brought to rest by applying brakes in 5 s. Calculate the retardation.
Solution
Given, Initial velocity (u) = 20 m/s-1
Final velocity (v) = 0
Time taken (t) = 5 s
Let acceleration be 'a'.
Using the first equation of motion,
∴ v = u + at
∴ 0 = 20 + 5a
∴ a = -4 m/s-2 ...(since negative acceleration is called the retardation)
Thus, retardation = 4 m/s-2
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