Inertia in Objects Introduction and Student Activities Moment of Inertia Movement of Common Objects Moment of Inertia Common Objects (Background Information) Moment of Inertia is the relationship and dynamics of rotational motion. Axis of Rotation- located at the center of an object. This is shown with a thin red line. Point Mass- first calculated to determine work required to rotate object. See equations in red This result is then the basis for all other movements of the selected object Overcoming Inertia Guests at a large table, in a Chinese restaurant, are selecting food dishes from a Lazy Susan. As each diner rotates the Lazy Susan, it must overcome the forces of inertia. Which illustration and equation best determines the movement of the Lazy Susan? Overcoming Inertia Guests at a large table, in a Chinese restaurant, are selecting food dishes from a Lazy Susan. As each diner rotates the Lazy Susan, it must overcome the forces of inertia. Which illustration and equation best determines the movement of the Lazy Susan? Answer: The last Susan undergoes rotational motion, while the dessert cart undergoes translational motion. Why: The lazy Susan has a fixed pivot at its center. This pivot never goes anywhere, no matter how you rotate the lazy Susan. Overcoming Inertia Guests at a large table, in a Chinese restaurant, are selecting food dishes from a Lazy Susan. Later, they select desserts from a cart. If the dessert cart experiences transitional motion, and the Lazy Susan experiences rotational motion; Which is more resistant to initial movement, or the moment of inertia? Explain why? Overcoming Inertia Guests at a large table, in a Chinese restaurant, are selecting food dishes from a Lazy Susan. Later, they select desserts from a cart. If the dessert cart experiences transitional motion, and the Lazy Susan experiences rotational motion; Which is more resistant to initial movement, or the moment of inertia? Explain why? Answer: The last Susan undergoes rotational motion, while the dessert cart undergoes translational motion. Why: The lazy Susan has a fixed pivot at its center. This pivot never goes anywhere, no matter how you rotate the lazy Susan. In contrast, the dessert cart moves about the room and has no fixed point. The server can rotate the dessert cart when necessary, but its principal motion in translational. Moment of Inertia Common Objects (Background Information) Moment of Inertia is the relationship and dynamics of rotational motion. Axis of Rotation- located at the center of an object. This is shown with a thin red line. Point Mass- first calculated to determine work required to rotate object. See equations in red This result is then the basis for all other movements of the selected object Why doesnt it fall? Precession Torque Why doesnt it fall Video HyperPhysics: Why doesnt it fall? Turning a bicycle A bicycle wants to go straight Gyroscopic action has a small effect. Precession Torque is produced counterclockwise. For example, If the rider leans left, torque in a counterclockwise precession of the wheel is produced. This torque turns the bike to the left. Why doesnt it fall? Turning a bicycle A bicycle wants to go straight If, Gyroscopic action has a small effect. Using the Right-hand Rule illustration. How does a moving bicycle not fall over? Turning a bike Precession The spin of angular momentum is along the axis of rotation. Torque at support then changes forces on the axis, or as shown, an axle. This circular motion is called Precession. FYI Any alteration in the position along rotational axis is known as precession