1Q10.70 • Moment of Inertia: Rotational Inertia of a Point Mass

Location: Cabinet 1

Photo shows the demonstration used at the University of Texas at Austin.

Concept conveyed:

Instructions:

Place the track on the base, tightening the screw. Slide one of the 300 g masses into the track leaving it loose by not tightening the screw on the top.
Put the stop screws at about the 24 cm mark on both ends of the track making sure to securely tighten them so they do not move.
Spin the track to see how the mass moves out from where it started based on how fast the rotations are. Notice that if the mass is at the center it doesn’t move, but if it is anywhere else on the track it moves.
Make sure to check the stop screws periodically to see if they have moved or become loose because of being hit by the mass! The mass will fly off the track if you do not keep tightening the screws!

Notes:

To put anything onto the track, line the square nut up with the grooves in the track and slide in.
Use a stable table, and make sure the base is level. Clamp down for best results.
The track scratches very easily, so be careful when tightening each component into place on the track.
Be gentle when spinning!

Demo Staff:

When putting the demo away, make sure to use the bags in the box for each part to prevent scratches.
Bags are labeled with what experiment uses each part, as well as what belongs inside.
This is a part of the Complete Rotational System from PASCO.

Last updated on July 31, 2026