Question

Two train each 50m long travelling in opposite direction with velocity 10mper s the time of crossing is

Answer 1

The velocity of 2nd train relative to first train is 15-(-10)=25m/s, when we say relative to first train then first train has to be considered stationary. With this picture second train has to travel 100 m with relative velocity of 25m/s. So, it will take 100/25=4s.