Question

a train 100 m long is moving with a velocity of 72 km h-1 . Find the time it takes to cross the bridge in 1 km hr

Answer 1

=>total distance=100+1000=1100m

=>velocity=72 km/h=(72 x 1000)/3600=20 m/s

=> speed=distance/time

=>•°• time=1100/20= 55 sec

Answer 2

The answer to the question is 55 seconds.

CALCULATION:

As per the question, the length of the train = 100 m.

We know that 1 km/hr = $\frac{5}{18}\ m/s$

The velocity of the train v = 72 km/hr.

                                           = $72\times \frac{5}{18}\ m/s$

                                           = 20 m/s

The distance of the bridge is 1 km.

                                               = 1000 m.

As the train is crossing the bridge, the train has to cross the distance equal to its length also. Hence, the total distance covered by the train will be -

                                         Total distance covered S = 1000 m+100 m

                                                                                    = 1100 m.

We are asked to calculate the time taken by the train to cross the bridge.

Hence, the time by the train t = $\frac{S}{v}$

                                                 = $\frac{1100}{20}\ seconds$

                                                 = 55 seconds.          [ans]