1. 8.2 Rotational Dynamics How do you get a ruler to spin on the end of a pencil? Apply a force perpendicular to the ruler. The ruler is the lever arm How do you move a door?

2. Torque Magnitude of the torque, , is the product of the force and the length of the lever arm. The force and lever arm must be perpendicular to each other. Units of N. m

3. The Moment of Inertia The placement of the mass makes a difference in the rotation of an object. If the mass is located in the center or at the edges. The resistance to rotational motion is called the moment of inertia, I. Moment of Inertia of a point mass, I=mr 2

4. Moments of Inertia is different for different shapes and different points of axis.

5. Newton’s 2 nd Law for Rotational Motion Angular acceleration is directly proportional to the net torque and inversely proportional to the moment of inertia.