Train A is moving along two parallel rail tracks towards north with 72 km h - 1 and train B is moving towards south with speed 108 km h - 1 . Velocity of train B with respect to A and velocity of ground with respect to B are (in m s - 1 ):

Step-by-step solution

V A = 72 km h - 1 = 72 × 1000 3600 = 20 m s - 1 and V B = - 108 km h - 1 = - 108 × 1000 3600 = - 30 m s - 1 Velocity of B w.r.t. A : V B / A = - 30 - 20 = – 50 m s - 1 Velocity of ground w.r.t. B : V G / B = 0 - - 30 = 30 m s - 1