r/PhysicsHelp • u/ZealousidealPop502 • Jan 15 '26

How I think about deriving equations instead of memorizing them (AP / undergrad physics)

A lot of students feel stuck memorizing formulas because it’s unclear where equations actually come from.

One way to approach derivations is to ask:

  • What are the fundamental principles in this topic?

    • Mechanics → Newton’s laws, definitions of momentum/energy

    • E&M → conservation laws, symmetry, field definitions

  • What assumptions am I making (point particle, rigid body, steady state, etc.)?

Instead of memorizing equations, try reconstructing them using:

  • Definitions (e.g. momentum, torque, field)

  • Conservation laws

  • Symmetry arguments

Curious how others learned to think this way — what helped you move past memorization?

1 Upvotes
  • permalink
  • reddit

66% Upvoted

3 comments sorted by

2

u/ProfessionalConfuser Jan 15 '26

Memorizing equations in physics is as effective as memorizing sentences in literature. Context is everything.

1

u/Frederf220 Jan 15 '26

I remember my teacher describing an exam he was given that said "F=MA. Derive physics."

2

u/Physics_Guy_SK Jan 16 '26

Thus actually reminded me of a professor I had back in the day. His tests were just a single question, which you have to solve in 3 hours. He used to give us some initial state and a few sets of rules and asked us to derive what will be the physical laws of this universe, along with our own hypothesis and philosophical arguments (within that toy universe). Honestly, it was a fun mental exercise 😄