Question

is zero relative velocity possible? explain

Answer 1

Yes, the zero relative velocity is possible.

Let us understand with an example.

For example: If you are traveling in a car which is moving at a velocity of 60 m/s with respect to ground. Your velocity will also be 60 m/s with respect to ground, but your relative velocity with respect to car is zero because you are part of the same car. Hence, the relative velocity can be zero.

Answer 2

Yes, it's absolutely possible bcoz when two bodies move with equal velocity in the same direction, then they have zero relative velocity.
Another case : Both the bodies are at rest w.r.t each other.