Question

A moves 65km/h while B is coming back of A with 80km/h.The relative velocity of B w.r.t A is

Answer 1

Imagine that you are A and you are running with a speed of 65km/hr and B who is coming back of you is running with a speed of 80km/hr.

as you are already running with a speed of 65km/hr you will see that B is running with a speed of (80 - 65)km/hr = 15km/hr

suppose if you are at rest and you are watching B who is running with a speed of 80km/hr then because you are at rest and your velocity is zero - you see that B is running with a speed of 80km/hr