This is a physics book by Benjamin Crowell that explains high school level conceptual physics.

Brief Contents:

1. Conservation of Mass and Energy
2. Conservation of Momentum
3. Conservation of Angular Momentum
4. Relativity
5. Electricity
6. Fields
7. The Ray of model of Light
8. Waves

For a semester-length course, all seven chapters can be covered. For a shorter course, the book is designed so that chapters 1, 2, and 5 are the only ones that are required for continuity; any of the others can be included or omitted at the instructor's discretion, with the only constraint being that chapter 6 requires chapter 4.