Two-dimensional motion expands the concepts of motion to cover change in two directions at once. At the core of this are the concept of vectors, and the independence of motion along each axis.
- A quantity that has both magnitude and direction (as velocity does) is a vector quantity.
- Inertial reference frames are constant velocity frames and are equivalent to each other.
- The relative velocity of one object compared to another can be computed using vector addition once the velocities of each object in their respective reference frame is known. Both frames have their velocities referenced to an “at-rest” reference frame.
- Vectors can be added graphically from head to tail and numerically by adding all the x−components of each vector together and all the y−components of each vector together.
- Projectile motion can be analyzed by considering independently the x− and y−components of the motion of the projectile.