---
title: "Mechanics textbook: motion, force and energy | Sandbox Physics"
description: "Volume 1 of the interactive physics textbook. Describe and measure motion, then test a constant-acceleration model against a recorded fall."
canonical_url: "https://sandboxphysics.com/learn/mechanics/"
language: "en"
page_type: "story"
alternate_languages:
  zh-CN: "https://sandboxphysics.com/zh/learn/mechanics/"
last_modified: "2026-10-28"
---

[Interactive Physics Textbook](https://sandboxphysics.com/learn/)

Volume 1

# Motion, Force and Energy

Volume 1 of the interactive physics textbook. Describe and measure motion, then test a constant-acceleration model against a recorded fall.

How do we describe and measure motion, predict it from forces, and solve it with energy and momentum?

Before this volume: High-school algebra, geometry and trigonometry. Derivatives, integrals and vectors are introduced where they are first needed.

## Chapters you can read now

### Unit 1: describing and measuring motion

Chapters 1 to 3 form one short unit. Chapter 1 reads motion from graphs, Chapter 2 turns camera frames into positions and velocity estimates, and Chapter 3 tests a constant-acceleration model against a recorded fall.

[Chapter 1 How do we describe a motion? The height of a position graph gives position, its slope gives velocity, and the signed area under the velocity graph gives displacement. Lab: Motion Graph Studio](https://sandboxphysics.com/learn/mechanics/describing-motion/) [Chapter 2 How does a camera measure motion? A camera records only pixels at fixed frames. Calibrate them into positions, estimate velocity from differences or local fits, and find where noise enters. Lab: Motion Measurement & Numerical Differentiation](https://sandboxphysics.com/learn/mechanics/measuring-motion-with-a-camera/) [Chapter 3 How do we test a constant-acceleration model? Fit release height, initial velocity and gravity to a recorded fall, read the residuals, and tell a precise result from an accurate one. Lab: Free Fall & Measuring Gravity](https://sandboxphysics.com/learn/mechanics/testing-constant-acceleration/)

## All chapters in this volume

1. Chapter 1 · [How do we describe a motion?](https://sandboxphysics.com/learn/mechanics/describing-motion/)

   What can one position–time curve tell us?

   Before this chapter: Coordinates and graphs of functions.

2. Chapter 2 · [How does a camera measure motion?](https://sandboxphysics.com/learn/mechanics/measuring-motion-with-a-camera/)

   Can pixels tell us velocity directly?

   Before this chapter: Chapter 1. Averages and the spread of repeated values are explained here.

3. Chapter 3 · [How do we test a constant-acceleration model?](https://sandboxphysics.com/learn/mechanics/testing-constant-acceleration/)

   How does one fall measure the acceleration of gravity?

   Before this chapter: Chapters 1 and 2. Fitting and residuals are introduced here; the matrix derivation is an optional section.

4. Chapter 4 · What changes for a different observer? in preparation

   How can one motion have different descriptions?

   Before this chapter: Chapters 1–3.

5. Chapter 5 · Why does a constant-speed turn still accelerate? in preparation

   How does velocity change around a bend?

   Before this chapter: Chapters 1 and 3, plus a short section on vectors.

6. Chapter 6 · How do forces change motion? in preparation

   Which forces belong on a free-body diagram?

   Before this chapter: Chapters 4 and 5.

7. Chapter 7 · When does a contact slip? in preparation

   When is friction strong enough to keep surfaces moving together?

   Before this chapter: Chapter 6.

8. Chapter 8 · How do ropes and pulleys link motions? in preparation

   Why can two connected bodies not accelerate independently?

   Before this chapter: Chapters 6 and 7.

9. Chapter 9 · How does a force along a path change kinetic energy? in preparation

   Why is the force at the end point not enough?

   Before this chapter: Chapter 6 and a short section on integrals.

10. Chapter 10 · When can we compare only the start and the end? in preparation

    How does potential energy simplify a motion problem?

    Before this chapter: Chapter 9.

11. Chapter 11 · What is conserved in a collision? in preparation

    Why must momentum and kinetic energy be checked separately?

    Before this chapter: Chapters 6 and 9.

12. Chapter 12 · Why does it matter where a force acts? in preparation

    How do we go from balance to rotation?

    Before this chapter: Chapters 5, 6, 9 and 11.

13. Chapter 13 · When does a rotation stay the same? in preparation

    Why does pulling in your arms make you spin faster?

    Before this chapter: Chapters 11 and 12.

14. Chapter 14 · How does one law of gravity explain falling and orbits? in preparation

    Why can a body keep circling a star or planet?

    Before this chapter: Chapters 5, 10 and 13.