Extra Credit: verify conservation of angular momentum

Verify the law of conservation of angular momentum.

This project may be done by teams of 1-2 individuals. The goal is to design an experiment in which the moment of inertia of a rotating object may be changed as it spins. For example, you might choose the object to be a person, holding a weight in each hand. The person can change his moment of inertia by spreading his arms out to each side, or pulling them into his body. You might choose a telephone: if the handset is placed on the base, the moment of inertia is small; if the handset flies off the base to the end of its cord, the moment of inertia is large. You must measure the angular velocity of the object before and after the moment of inertia changes, and calculate the angular momentum before and after the change. You must show, by careful measurement, that the angular momentum of the object remains the same before and after the change.

Draw a picture of the experiment, showing all relevant details; include one picture before the change, and one after. Before you start the object spinning, measure its moment of inertia in each of the two states. Carry out the experiment, making at least three trials. Record the angular velocity before and after the change in each trial.

For each trial, compare the angular momentum in each of the two states. Are they the same? If not, try to explain the difference.

Submit a report which contains the pictures and descriptions of your experiment, as well as all calculations and the results. You may also include interesting items you discovered during the course of the procedure.

This page maintained by Michael Richmond. Last modified Mar 18, 1997.