Question

An electric train is running at 90km/hr.on stopping electric supply to the train engine the train moving with a constant negative acceleration comes to a halt in 20 seconds. Calculate the acceleration of the train and the distance covered by the train during this time.

Answer 1

initial speed of electric train, u = 90 km/h = 90 × 5/18 = 25 m/s

on stopping electric supply to train engine , the train moving with a constant negative acceleration i.e., -a m/s² comes to halt in 20 second.

final speed of train , v = 0

using formula, v = u + at

or, 0 = 25 - a × 20

or, a = 1.25 m/s²

hence, magnitude of acceleration is 1.25 m/s²

now distance travelled by train be s.

so, s = ut + 1/2 at²

= 25 × 20 + 1/2 × (-1.25) × (20)²

= 500 - 1/2 × 1.25 × 400

= 500 - 250

= 250 m