Question

If Va and Vb are the velocities of the two trains A and B moving along the parallel tracks what is the relative velocity between them when they 1.approach each other 2.recede each other

Answer 1

Velocity of train A = Va

Velocity of train B = Vb

If trains are moving in same direction

Velocity of A w.r.t B (Vab) = (Va-Vb)

Velocity of B w.r.t A (Vba) = (Vb-Va)

If trains are moving in opposite directions

Now we will take one direction positive and the other negative

Velocity of A w.r.t B (Vab) = (Va -(-Vb))= (Va+Vb)

Velocity of B w.r.t A (Vba) = (Vb-(-Va))= (Vb+Va)