CK-12 Physics FlexBook

The CK-12 Physics FlexBook is a free, open-source high school physics textbook published by the CK-12 Foundation. Covering the complete curriculum of a standard Physics I course, this digital textbook provides clear, rigorous explanations of fundamental physics concepts with worked examples, diagrams, and interactive practice problems.

The textbook is organized into major physics domains including kinematics and motion, forces and Newton's laws, work and energy, momentum and collisions, circular motion and gravitation, waves and sound, light and optics, electricity and circuits, magnetism and electromagnetism, and an introduction to modern physics including relativity and quantum mechanics. Each chapter follows a logical progression from concepts to applications with real-world examples throughout.

Like all CK-12 FlexBooks, the Physics textbook features adaptive practice technology that adjusts problem difficulty based on student performance. This intelligent practice system helps students build confidence on foundational problems before advancing to more challenging applications, providing a personalized learning path through the material.

The FlexBook includes numerous diagrams, graphs, and vector illustrations essential for physics instruction, all rendered clearly in the digital format. Many sections link to CK-12 physics simulations where students can manipulate variables and observe results in real time, reinforcing conceptual understanding through hands-on virtual experimentation.

For homeschool families preparing students for AP Physics, SAT Subject Tests, or college-level coursework, the CK-12 Physics FlexBook offers a solid foundational curriculum at no cost. The content is comparable in scope to popular commercial physics textbooks and can be supplemented with CK-12 video lessons, practice problems, and virtual labs for a complete physics education experience.