Question

A train is moving with the velocity of 20m/s.It stops after 10 seconds when brakes are applied.calculate its retardation​

Answer 1

Answer:

This is Your Answer

Explanation:

The body(train) was moving with a velocity of 20m/s.

the driver must have put on brakes…such that it stops after 10 seconds.

so a deceleration or retardation due to brakes has reduced the speed to zero.

in one sec if the retardation is say a m/s^2 then in 10 sec it will reduce the velocity by 10 times a m/s^2

therefore

10 s. a m/s^2 = the initial velocity before the breaks was put on = 20 m/s

so a the retardation = 20/10 = 2m/s^2

or one can use kinematical relation

final velocity at time t say v = initial velocity - retardation. time

v(10sec) =0 = 20 m/s - a . 10 s

and one gets to the above result.

However if in another problem an acceleration is happen

then v(t) = u (t=0) + a.t

Answer 2

We will utilise the first law of motion here
V = u + at
As it stops,
V = 0
U = 20 m/s
T = 10 s

0 = 20 + 10a
-20 = 10a
-2 = a

Hence it’s retardation is -2 m/s^2

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