Question

a 100 metre long train crosses a man travelling at 5 km per hour in opposite direction at the time 7.2 seconds then the velocity of train is

Answer 1

we apply a simple logic, if train and man cross each-other in opposite direction then respective velocity is equal to the addition of both the velocities.

suppose the velocity of train = v,

velocity of man = 5 km/h, time taken t= 7.2 s, distance = length of train = 100 m.

respective velocity = (v + 5) km/h

here we apply just a simple formula i.e. velocity = distance/time

(v+5) km/h = 100/7.2 m/s, Or v = 13.89 m/s - 5 km/h, Or (since 1 km/s = 5/18 m/s)

v= 13.89 m/s - 5*(5/18) m/s Or v= 13.89 - 1.389 m/s Or (since 1 m/s = 18/5 km/s)

v = 12.5 m/s Or 45 km/h

Answer 2

This is your answer I hope it's right