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5.4 Rotational Inertia

Part of Torque and Rotational Dynamics in AP® Physics C: Mechanics. Read the opening section, then create a free account for the full interactive lesson, practice, and progress tracking.

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Rotational Inertia (Moment of Inertia)

Rotational inertia —also called the moment of inertia —quantifies an object’s resistance to changes in rotational motion. It plays the same role in rotational dynamics that mass plays in linear dynamics:

Mass resists changes in linear velocity.

Rotational inertia resists changes in angular velocity.

Rotational inertia is a scalar, measured in kilogram–meter² (kg·m²), and represented by I.

In this unit

6 lessons

  1. 5.1Rotational KinematicsPreview lesson
  2. 5.2Connecting Linear and Rotational MotionPreview lesson
  3. 5.3TorquePreview lesson
  4. 5.4Rotational InertiaThis lesson
  5. 5.5Rotational Equilibrium and Newton’s First Law in Rotational FormPreview lesson
  6. 5.6Newton’s Second Law in Rotational FormPreview lesson

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