AP Physics 1 · Unit 5 · Torque and Rotational Dynamics

Rotational Kinematics

Measure rotation in radians, compare angular-motion graphs, and connect a rotating point’s speed and acceleration with its radius.

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Learn by doing

Three ideas you’ll put into motion

Use angular position, angular velocity, and angular acceleration with consistent signs.

Interpret angular graph slopes and areas, then apply constant-angular-acceleration relationships.

Relate radius to tangential speed and distinguish tangential from inward acceleration.

The big idea

Angular velocity measures how fast angular position changes. Angular acceleration measures the rate of change of angular velocity.

For a point on a rigid rotating object, v = r|ω|. Tangential acceleration has magnitude r|α|; inward acceleration has magnitude rω².

A quick comparison

Compare two points on the same rigid wheel at a given instant.

Same angular velocity; larger radius means greater tangential speed.

Teaching this topic?Classroom fit, AP connections, and support

Classroom fit: Use for a concept introduction, guided independent practice, or a projected class discussion.
Before students begin: Linear kinematics, radians, slope and area, and centripetal acceleration.
Built-in support: Prepared scenes, guided prompts, and feedback on lesson questions.
AP Physics 1 connections: Unit 5: rotational kinematics and connections between linear and angular motion.
Check for understanding: Ask which quantities are the same for all points on a rigid wheel and which depend on radius.

The first scene is set up. Start the lesson and explore.