Chapter 4 — Motion in 2D and 3D

📚 Reference: Halliday, Resnick, Krane — Physics (4th ed.), Vol 1, Chapter 4.

What this chapter is about

Chapter 2 gave 1D kinematics; Chapter 3 built the vector language. Now we combine them: 2D and 3D kinematics. A projectile's flight, a satellite's orbit, a charged particle in a magnetic field, a car in a turn — all rest on the same foundation.

Key idea: position, velocity, acceleration all become vectors. The equations look like Chapter 2's, with scalars replaced by vectors.

Sections

1. 4.1 — Position and displacement vectors
2. 4.2 — Velocity and acceleration vectors
3. 4.3 — Projectile motion
4. 4.4 — Uniform circular motion
5. 4.5 — Relative motion — inertial frames
6. 4.6 — Worked problems
7. 4.7 — Practice problems
8. 4.8 — Further reading
9. 4.9 — Q&A

Prerequisites

• Chapter 2 — 1D kinematics, derivative and integral concepts
• Chapter 3 — vectors, components, vector addition
• Trigonometry — sin, cos, tan
• Basic derivatives — since velocity is the derivative of position

Reading suggestion

• §4.1 and §4.2 are foundational — vector kinematics
• §4.3 (projectile) and §4.4 (circular) are two classical applications — together the heart of the chapter
• §4.5 (relative velocity) builds intuition useful for special relativity later

Why this chapter matters

Most everyday physics is 2D or 3D:

• A soccer ball, an arrow, a fountain — all projectiles
• A car in a turn, the Moon around Earth, an electron in an antenna — all circular or quasi-circular
• Two drivers comparing speeds — relative velocity

Without Chapter 4, real physics can't be described.

📖 Open reference: OpenStax University Physics Vol 1 — Chapters 3 & 4.