Question

a train travelling with 130kmph crossed a cycle which travelled with a speed of 10kmph in 45 secs calculate length of the train.

Answer 1

V = speed of train = 130 kilometer/hour

v = speed of cycle = 10 kilometer/hour

Since both the train and cycle move in same direction , the relative speed of train relative to the cycle is given as

V' = V - v

inserting the above values in the above equation

V' = 130 - 10

V' = 120 km/h

t = time taken by the train to cross the cycle = 45 sec  = 45/(3600) = 0.0125  hours

(Since 1 hour = 3600 sec)

L = length of the train

distance traveled by the train at its relative speed in time to cross the cycle is same as the length of the train, hence

L = V' t

inserting the above values in the above equation

L = 120 x 0.0125

L = 1.5 km