*Question*:What is relative velocity?

When two objects are both moving, the rate at which the distance between them changes with time is called the relative velocity.

Example: If two cars are travelling towards each other at 40 m/s. We say the relative velocity is 80m/s because the distance between them is getting smaller at a rate of 80 meters every second.

Alternatively if two cars are travelling in the same direction at different speed, the relative velocity is the rate at which the distance between the two cars increases per second.