Question

A moving train is brought to rest within 20sec by applying brakes. Find the initial velocity, if the retardation due to brake is 1.5m/s^2

Answer 1

Let the initial velocity of the train = u

Retardation due to brakes (a) = - 1.5 m/s^2

Time taken to come to rest (t) = 20 sec

Final velocity (v) = 0 m/s (As it it coming to rest)

Now, using first equation of motion:

$v = u +at$

$0 = u - 1.5 \times 20$

u = 30 m/s

Hence, the initial velocity of the train is 30 m/s.