> For the complete documentation index, see [llms.txt](https://knowmayus.gitbook.io/physics/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowmayus.gitbook.io/physics/definitions.md).

# Definitions

Propagation: The process by which a disturbance, such as the motion of electromagnetic or sound  waves is moved a medium.

Contact Forcess: Forces that occur when two objects are in contact with one another.

**Normal Force:** When a contact Force acts perpendicular to the surface of contact.