Definition:Relative Velocity

Definition

Let $A$ and $B$ be bodies in ordinary space.

Definition 1

Let the frame of reference $\RR$ be such that $B$ is stationary with respect to $\RR$.

Let $\mathbf v_{AB}$ be the velocity of $A$ with respect to $\RR$.

Then $\mathbf v_{AB}$ is the velocity of $A$ relative to $B$.

Definition 2

Let $\mathbf v_A$ and $\mathbf v_B$ be the velocities of $A$ and $B$ in some frame of reference $\RR$.

The velocity $\mathbf v_{AB}$ of $A$ relative to $B$ is defined as:

$\mathbf v_{AB} := \mathbf v_A - \mathbf v_B$

Also see

• Definition:Relative Acceleration

• Results about relative velocity can be found here.