Question

A moving train is brought to rest within 20 second by applying brakes. Find the initial velocity if the retardation due to brakes is 2m 5-2

Answer 1

retardation = 2 m/s²
time = 20 sec
final velocity ( V) = 0
initial velcity (u) = ?
use formula ,
V = u + at
0 = u -2× 20

u = 40 m/s

Answer 2

The initial speed of the train is 40 m/s.

Explanation:

It is given that,

Retardation applied due to brakes, $a=-2\ m/s^2$

Time taken, t = 20 s

Final speed of the train, v = 0 (as it comes to rest)

Let u is the initial speed of the train. Using the first equation of kinematics to find it as :

$v=u+at$

$u=-at$

$u=-(-2\ m/s^2\times 20\ s)$

u = 40 m/s

So, the initial velocity of the train is 40 m/s. Hence, this is the required solution.

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