Question

The driver of the train travelling at 40m/s applies the brakes as the train enters a station. The train slows down at a rate of 2m/s^2.The platform is 400 m long.Will the train stop in time?

Answer 1

May be 20 second... Not sure

Answer 2

Initial speed = u = 40m/s
Final speed = v = 0m/s
(Final speed will be zero because it stops means it is in a rest )
Acceleration = a = 2m/s²
Time = t = ?

a = (v-u)/t
at = v-u
t = (v-u)/a
t = (0-40)/2
t = -40/2
t = -20s
(- will show the acceleration will be apposite direction)

So train stops in 20 second