AP Physics C: Mechanics · Unit 0: Calculus Primer ·  Lesson 0.2

The Power Rule for Derivatives

Turning yesterday's limit into a two-second shortcut  ·  Approx. 1–2 class days

Starringd/dx(xⁿ) = nxⁿ⁻¹d/dx[c·f(x)] = c·f'(x)

Use this as a quick reference for the power rule, linearity, and applying both to negative and fractional exponents.

The Power Rule for Derivatives infographic

🧭 Plot Summary

Lesson 0.1 found derivatives from scratch, using a limit, every single time. That's a great way to understand why a derivative works — a terrible way to actually get through a physics problem set. The power rule is the shortcut that pattern-matches what you already discovered: bring the exponent down as a multiplier, then subtract one from it. Pair that with two more rules — how to handle constants multiplying a function, and how to handle functions added together — and you can differentiate almost any polynomial you'll meet this year on sight.

What you'll do in this lesson

  • See where the power rule pattern comes from — a direct callback to Lesson 0.1's results.
  • Differentiate full polynomials term by term using the constant multiple and sum rules.
  • Extend the power rule to negative and fractional exponents.
  • Rewrite roots and reciprocals as powers so the rule actually applies.
  • Differentiate a real kinematics equation, x(t), all the way down to a(t).

Why it matters

Nearly every position function you'll differentiate in Unit 1 is a polynomial in t — things like x(t) = x₀ + v₀t + ½at². The power rule is what turns that into v(t) = v₀ + at in about five seconds, instead of a full limit computation.

Self-Check Before You Roll On

Check off each item as you get there. These aren't grades — they're your own signal.