Question

on a railway track a driver applies the brakes of the train at a yellow signal, a distance 1 km from red , where
it stops. The max deceleration of the train iş 0.2 m/s. Assuming uniform deceleration
what is the maximum safe speed of the train at the yellow signal? 2012- 65 Eng:
(a) 20 m/s (b) 40 m/s (c) 200 m/s (d) 400 m/s​

Answer 1

Answer:

20 m/s

Explanation:

on a railway track a driver applies the brakes of the train at a yellow signal, a distance 1 km from red , where   it stops. The max deceleration of the train iş 0.2 m/s.

Let say speed at Yellow signal = U m/s

V = final speed  = 0 m/s

a = acceleration  = - 0.2 m/s  (as deceleration)

S = distance = 1 km  = 1000m

V² - U² = 2aS

=> 0² - U² = 2(-0.2)*1000

=> -U² = - 400

=> U² = 400

Taking square root both sides

=> U = 20

the maximum safe speed of the train at the yellow signal = 20 m/s

option a is correct