Loaded Disk
Purpose
Demonstrates that rotation appears smooth when viewed about the center of mass but wobbles when viewed about the geometric center. Students see directly why center of mass is the natural reference point for rotational motion.
Figure 1:
Side showing the geometric center. When this side faces students during rotation, the disk appears to wobble.
Figure 2:
Side showing the circle painted around the actual center of mass. When this side faces students, the circle appears to rotate smoothly.