Angular Momentum Rotational Inertia Rotating objects have a

Angular Momentum Rotational Inertia

• Rotating objects have a tendency to continue rotating. Non-rotating objects have a tendency to not rotate. ØRotational Inertia describes these tendencies. • Linear Inertia is simply the object’s total mass. • Rotational Inertia depends on the distribution of an object’s mass as well.

• Objects with more mass near the center of rotation have smaller moments of inertia.

• Torques can cause a change of angular momentum. ØJust as forces can cause a change in linear momentum. • Angular momentum is conserved, as well. • Linear momentum is p = mv • Angular momentum is L = Iω • It is important to know the angular velocity of a rotating object. ØThe magnitude of ω tells the angular speed. ØThe direction represents the axis of rotation, and its orientation.

• Use the Right Hand Rule to determine the angular velocity of a rotating object! Ø 1) Orient your right hand so that your fingers curl in the direction of the rotation Ø 2) Your thumb points in the direction of the axis of rotation. Ø 3) This represents the “angular velocity” of the rotating object.

• Applying conservation: • I 1ω 1 = I 2ω 2 • Conservation of Angular Momentum explains the skater’s change of speed when she changes the location of her limbs. • Hint: Changes in linear mass are rare. Changes in moments of inertia are common and should be expected in problems.