Question

A moving train brought to rest within 20 seconds by applying brakes . Find the initial velocity, if the retardation due to brakes is 2 ,metre /second​

Answer 1

Answer:

Let, u be the initial velocity

Retardation is a Time is t

Velocity is v

We know,v = u + at

As, the train stops so v = 0 Time t = 20s

Retardation a = 15m/s

Therefore, according to the formula u = 0 + (15*20) = 300 m/s.

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Answer 2

Answer:

Initial velocity of the train

= 40 m/s

Step by step explanations :

Given that,

a moving train brought to rest within 20 seconds by applying brakes

here,

final velocity of the train = 0 m/s

let the initial velocity of the train be u

given retardation produced by the brakes = 2 m/s²

so,

acceleration = -2 m/s²

given time taken to stop = 20 seconds

now we have

Initial velocity (u) = u

final velocity(v) = 0 m/s

acceleration(a) = -2 m/s²

time taken(t) = 20 seconds

by the equation of motion,

v = u + at

putting the values,

0 = u + (-2)(20)

u - 40 = 0

u =40m/s

so,

Initial velocity of the train

= 40 m/s