Chapter 5 — Newton’s laws of motion

What this chapter is about

Chapters 2 and 4 were kinematics — "how to describe motion". Now the key question: why does motion happen? Answer: force. Newton in 1687 stated three laws from which all classical mechanics follows.

Sections

1. 5.1 — The concept of force and interaction
2. 5.2 — Newton's first law — inertia
3. 5.3 — Second law — F=ma
4. 5.4 — Third law — action and reaction
5. 5.5 — Weight and mass
6. 5.6 — Friction
7. 5.7 — Applications — pulleys, inclined planes
8. 5.8 — Worked problems
9. 5.9 — Practice problems
10. 5.10 — Q&A

Prerequisites

• Chapter 2 — 1D kinematics, acceleration
• Chapter 3 — vectors, addition
• Chapter 4 — 2D/3D kinematics

Why this chapter is the heart of physics

\vec F = m\vec a — three letters, but all mechanics rides on it. From falling apples to satellite orbits, from walking to earthquakes — all described by this one equation.