Relative motion is the motion which is computed on the grounds of motion of an object in contrast to another moving motion. The relative term is not conferring to earth but is basically the velocity of the object taken as static when equated to other moving bodies.
Similarly, when an object moves it also alters its position constantly and that is in relative to some reference point generally a detection instrument or maybe a separator.
Let us assume the velocity of object A comparative to B is ‘v’ then the velocity of object B comparative to A is ‘-v’
Situation One:
Two objects are moving in the same direction then the relative motion is an object with greater speed – object with minor speed.
Relative speed = Speed of object A (better speed) – speed of object B (lesser speed)
Situation Two:
One object is moving, though the other one is being stationary.
Relative speed = Speed of moving object – stationary object (zero)
Situation Three:
Both objects are moving in the opposite direction
Relative speed = Speed of object A + speed of object B