If v1 and v2 are the velocities of two bodies then what is their relative velocity when they move in the 1. same and 2. opposite direction?

Question

If v1 and v2 are the velocities of two bodies then what is their relative velocity when they move in the

1. same and

2. opposite direction?

Answer 1

1. When the bodies move in the same direction, the relative velocity of 1st body w.r.t 2nd is v12 = v1 – v2

2. When the bodies move in the opposite directions, the relative velocity of 1st body w.r.t 2nd is v12 = v1 + v2.