Question

A railway train 200m long moves with a speed of 72km per hour. Calculate the time taken by the train to cross a brigde 0.8k.m long.

Answer 1

total distance of bridge in meteres=0.8*1000=800 m

speed=72kph=72*1000/3600

speed=20 m/s

time taken by train to travel 200 m that is in crossing a point

t=dist/spd

t=200/20=10secs

now very important point

length of bridge is 4 times of train

so time taken to cover the distance of bridge=4*10=40 secs

now to cross the bridge completely it will need 10 more secs because the train has to cross the bridge that is it must not be on the bridge

so total time taken is 40+10=50 secs

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