Relative velocity  Kinematics in Two Dimensions
Relative velocity
Lessons
Notes:
In this lesson, we will learn:
 How to solve relative velocity problems in one dimension
 How to solve relative velocity problems in two dimensions
Notes:
 Frame of reference can be thought of as the point of view that measurements are made from.
 A relative velocity is a velocity that is measured in a frame of reference. Usually, a moving object is the frame of reference.
 Imagine you are on a train leaving a station at 10 m/s [E]. A bystander at the station would see the train move at 10 m/s [E]: this is the velocity of the train relative to the station ( $\vec{v}_{train\,to\,station}$ ). The frame of reference is the station, since that is what the velocity is measured from.
 If you imagine yourself looking out the window of the train it might appear that the station is moving 10 m/s [W], even though you know that it is the train that is moving. This is the velocity of the station relative to the train ( $\vec{v}_{train\,to\,station}$ ) and the frame of reference is the train.

Intro Lesson
Introduction to relative velocity

2.
Relative velocity in two dimensions