AP Course

AP Physics C: Mechanics

Updated for the AP Physics C: Mechanics framework effective fall 2024, with calculus-based derivations, labs, quizzes, and practice.

Build calculus-based mechanics with original derivations, experiments, quizzes, and practice sets.

AP Physics C: Mechanics · Unit 2 · Topic 2.10

Circular Motion

Vector force models and differential equations determine center-of-mass motion in constrained and curving systems.

1. Topic Lens

Circular Motion is studied through force and translational dynamics. Connect the system boundary, interacting parts, and measurable evidence before applying a formula.

\[\sum\vec F=\frac{d\vec p}{dt}\]

2. Why the Formula Works

The relationship is built from definitions and conservation reasoning:

  1. For constant mass, momentum p=mv gives dp/dt=m dv/dt.
  2. When force is position-dependent, apply the chain rule dv/dt=(dv/dx)(dx/dt).
  3. Since dx/dt=v, the equation becomes F=mv dv/dx and can be integrated.
\[\sum F_x=m\frac{dv}{dt}=mv\frac{dv}{dx}\]

3. Detailed Visual Model

Pixel diagram for Circular MotionOriginal schematic connecting Circular Motion to Force and Translational Dynamics.
Circular Motion: an original pixel-style model. Use it as a schematic, not a literal scale drawing.

4. Worked Example and Lab Link

A constant net force of 8 N acts on a 2 kg mass. Find acceleration.

Answer: a=8/2=4 m/s².

Investigation idea: Measure force and acceleration for a changing-mass cart system and compare a numerical differential-equation model.

Common trap: Centripetal force is the inward net force, not an extra force to add to the free-body diagram.

Checkpoint · Topic 2.10

Explain how circular motion supports or limits this conclusion: a=8/2=4 m/s².

Official curriculum reference: College Board AP Physics C: Mechanics course page. The explanation and worked example are independently written for this study site.