Radian:
A unit of rotational displacement; one revolution equals 2 ∏ radians.

Angular Velocity:
Also called rotational speed, the number of rotations or revolutions per unit of time, often measured in rpm, revolutions per minute.

Table of rotational motion formulas, and the related linear motion formulas:

Torque:
The rotational quantity that causes rotation; the product of force times lever arm.

Moment of inertia:
Also called rotational inertia, The rotational equivalent of linear inertia; a measure of the ease of rotating some object.

Newton’s second law for rotational motion:
Σ Τ=I α The sum of the torques is equal to the rotational inertia times the angular acceleration.

Rotational Equilibrium:
The situation when the net torque on an object equals zero.

Angular momentum:
The rotational equivalent of linear momentum that describes the tendency of an object to continue rotating.

Instead of moving in a straight line, many object rotate.  This rotation can be described with terms and formulas that are analogous to linear motion descriptors. For example, in linear motion a force causes a mass to accelerate.  In rotational motion, a torque causes a mass with some amount of rotational inertia, to exhibit angular acceleration.  The concepts are very similar.  Also, just as an object could be in equilibrium when the forces on it add up to zero, an object can be in rotational equilibrium when the net torque on it is zero.  When studying these new concepts, apply your previous knowledge of linear motion.

Specific Tutorial Features:

• Diagrams to illustrate the lever arms, angles, and other quantities encountered in problems.
  
• Animated diagrams to actually show the rotational motion.
  
• Problem-solving techniques are used to work out and illustrate the example problems, step by step.

Series Features:

• Concept map showing inter-connections of new concepts in this tutorial and those previously introduced.
  
• Definition slides introduce terms as they are needed.
  
• Visual representation of concepts
  
• Animated examples—worked out step by step
  
• A concise summary is given at the conclusion of the tutorial.

Angular motion compared to linear motion

• Angular displacement, angle
  
• Angular speed
  
• Angular acceleration
  
• Related formulas

Torque

• Units  
  
• Direction
  
• Applications

Moment of Inertia

• Description
  
• Example
  
• Formulas

Rotational Equilibrium

Angular Momentum

• Formula
  
• Conservation of angular momentum
  
• Examples