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Learning Introductory Physics with Activities

Section 13.9 Challenge - Moments of Inertia

Explanation 13.9.1. Balancing Bat.

You spend some time experimenting with a baseball bat, and eventually you are able to balance the bat on a single finger. A friend notices this, and makes the following claim:
“It looks like the balancing point isn’t in the middle of the bat—it’s a little closer to the thicker end of the bat. That balancing point must be the location where half the bat’s mass is on the left and half the bat’s mass is on the right.”
How would you respond to your friend’s claim? Is your friend’s claim correct, partially correct, or incorrect?

A*R*C*S 13.9.2. The Cube I.

A wooden cube with side length \(L\) and total mass \(M\) is rotating about an axis passing through one of its edges. Use an integral to calculate the moment of inertia.

Explanation 13.9.3. The Cube II.

The cube from the previous activity is instead rotating about an axis passing through its center (and through the center of one of its faces). The parallel axis theorem can be used to demonstrate that the moment of inertia about this axis is smaller than the moment of inertia about the axis in the previous activity. Give a qualitative explanation accounting for this result.

Activity 13.9.4. Metacognitive Reflection.