Relative velocity is a measurement of velocity between two objects as determined in a single coordinate system. Relative velocity is fundamental in both classical and modern physics, since many systems in physics deal with the relative motion of two or more particles. In Newtonian mechanics, the relative velocity is independent of the chosen inertial reference frame. This is not the case anymore with special relativity in which velocities depend on the choice of reference frame.
If an object A is moving with velocity vector v and an object B with velocity vector w, then the velocity of object A relative to object B is defined as the difference of the two velocity vectors:
Similarly the relative velocity of object B moving with velocity w, relative to object A moving with velocity v is:
Usually the inertial frame is chosen in which the latter of the two mentioned objects is in rest.
Read more about this topic: Velocity
Famous quotes containing the word relative:
“It is an interesting question how far men would retain their relative rank if they were divested of their clothes.”
—Henry David Thoreau (1817–1862)