Next: Suggested Problems Up: Rotation of Rigid Bodies Previous: Rotational Kinetic Energy and

Newton's Second Law for Rotating Rigid Bodies

The general motion of a rigid body can be completely described by the linear motion of its center of mass and its rotation about the center of mass.

Newton's Second Law therefore has two parts:

Linear Motion

where is the net force on the object, M is the total mass, is th acceleration of the center of mass of the object, and is its total linear momentum.

Rotational Motion

where is the net torque on the object, I is its moment of inertia about its center of mass, and is its angular moment about the center of mass.

Note

• When applying Newton's laws to solve for the motion of a system of objects, one must apply the rotational version of the Second law to each extended object in the system that is free to rotate.
• In the absence of net external torque the total angular momentum of any system of objects (about any axis) is conserved.

Next: Suggested Problems Up: Rotation of Rigid Bodies Previous: Rotational Kinetic Energy and
gabor@theory.uwinnipeg.ca
2001-01-05