When will the relative velocity of two moving objects be zero?

Hint: The term “relative” in relative velocities refers to the difference in the velocity of both the moving objects. In order to answer this problem we have to consider the different cases of velocities of two moving objects.

Complete step by step solution:
We have to find the relative speed of two objects. It can be said that their relative velocities will be zero if and only if they move in the same direction. We will try to think that one of the moving objects is trying to catch up to the others at a constant rate.

Case 1: We can say that whenever the two objects come at a point where their velocities become equal or equivalent to each other, then their relative velocities will become zero.

Case 2: As we have to find the relative velocities of two objects, their velocity need not be equal, so even then there might be a point that the objects stop at some stage. In that case we say that as their velocities are zero, then their relative velocities will also be zero.

So the relative velocity of two moving objects will be zero when both their velocities are equal or both their velocities are zero moving in the same direction.

Note: The objects should move in the same direction as if they move in the different direction, along the same line, it will be that both objects are moving away from each other, and in that case, their relative velocity will increase instead of decreasing.