Question

a moving train is brought to rest within 20 seconds by applying brakes . find the initial velocity if the retardation due to brakes is 2m per second^2​

Answer 1

apply v=u+at

v= final velocity =0 (since train stops)

u= initial velocity =?

a= acceleration= -2 ( since it will stop the train so it will be in opppsite to direction of motion better known as retardation)

t= time =20 sec.

so we get

u = 2x20

= 40 m/sec

Answer 2

Solution:

Given,

Time, t = 20 s

Retardation, a = -2 m/s^2

Final velocity = 0

Here, retardation means if the speed of a particle or object decreases, we say that it is decelerating or it has a retardation.

By using the formula of acceleration

a = v - u / t

Therefore, v = u + at

=> v = u + at

=> 0 = u + (-2) × 20

=> 0 = u - 2 × 20

=> u = 40 m/s

Therefore, u = 40 m/s

Thus, the initial velocity of train is 40 m/s.