Angular Momentum Experiment

Part I: Calibration

The web page has the LabVIEW screens from when I did the experiment. You will obtain your own results, but I include mine here in case you might find them useful. Your results may be different.

Main Menu Image

The main pull-down menu for the Angular Momentum program is shown in the figure above.

The graph above also shows the result my measurements to calibrate the tachometer generator output. After I typed in 7 for the number of periods, this is the result of the computer's calculation.

Calibration Result

Moment of Inertia

Here is the 55 gm weight ready to be dropped in order to determine the rotor moment of inertia. (The rotor is held by a paper clip so that I could take the photo.)

Calibration Result

This shows the graph of ω vs. t while the weight was falling and the while the rotor was coasting to a stop. The portion where the weight was falling has been fit to a straight line and gave the result α1 = 88.7 ± 0.4 s-2.

Calibration Result, Falling Weight

Here is the graph and fit for the time when the rotor was coasting to a stop. The fit gave α2 = −31.2 ± 0.2 s-2.

Calibration Result, Coasting

Note: if the string does not pull out cleanly or for some other reason the part of your graph where the rotor is coasting does not have good data, you do not need to repeat the measurement. Instead, make the 10 second coasting measurement (see below) and fit the data for ω < 125 s-1 to find α2.

Here is the moment of inertia calculation result for my apparatus.

Moment of Inertia Calculation Result

Here is a graph of the 10 second coasting down measurement referred to above. The rotor began with ω > 475 s-1 and slowed to ω = 75 s-1. The non-linearity of the graph shows that α is not constant and thus that the friction is not quite constant.

Rotor Coasting for 10 seconds

Part II: Angular Collisions

Slow Collision

Here is a graph of my raw measurements of ω vs. t during the slow collision.

Graph of the slow collision

Here is the fit to find αrotor during the slow collision.

Acceleration during slow collision

Here is the Results tab from the above fit for the slow collision.

Acceleration during slow collision

Fast Collision

Here is a graph of my raw measurements of ω vs. t during the fast collision.

Graph of the fast collision

This shows an expanded time scale plot of the fast collision. You can see this collision lasts about 30 ms.

Expanded graph of the fast collision

This is a link to my report for Experiment 05.

J. D. Litster, November 6, 2007.