We need a coordinate system to specify the positions and motion of objects. This video explains what a coordinate system is and how to set up one for one dimensional and two dimensional cases.
Relevant chapter: Motion in a straight line
The music at the beginning is from https://www.lineshjose.com.
Lesson download: https://utube-resources-63b002.gitlab.io/physics11/coords_system/
If you want, you can try out the demonstrations shown in the video here:
3D coordinate system: https://utube-resources-63b002.gitlab.io/physics11/3d_coord_system
Bouncing ball: https://utube-resources-63b002.gitlab.io/physics11/bouncing_ball
Motion in a plane: https://utube-resources-63b002.gitlab.io/physics11/plane_motion