Moment of Inertia Rods

In this demonstration, students try to rotate two rods of the same mass. One is much easier to rotate than the other as their masses are concentrated differently. This gives the rods different moments of inertia.

Setup:

Place the moment of inertia rods on the lab table.

The instructor will need one or two student volunteers. The student should grip the rod at its center and try to rotate it as quickly as possible.

The red rod is much easier to rotate as the mass is concentrated at its center. The yellow rod has mass concentrated at its ends, therefore it has a greater moment of inertia and is harder to rotate.

Notes:

None

Courses Used In:

• PHY 10111

• PHY 10310

• PHY 10410

• PHY 30210

Discussion and Polling Questions:

• If the mass of the two rods is the same, does mass alone affect how easy a rod is to spin?

• Which rod is harder to spin?

• What is different about the two rods?

• Where is the mass concentrated in rod 1?

• Where is the mass concentrated in rod 2?

Equipment Needed:

• Red Moment of Inertia Rod

• Yellow Moment of Inertia Rod