Moment of Inertia

In the basement of the Annex, tucked away in a classroom called “the Physics Cave,” generations of students have met to learn the laws of gravity, motion, and more in Physics class. 

One student wound string around the base of a T-shaped PVC pipe. Two students clamped textbooks to the edge of a table. “Can I use your iPhone for a sec?,” another student called across the room, “I want to use your phone as a level.”

They were trying to figure out the moment of inertia for an irregular object, but first they had to design an experiment that would measure it.

Physics teacher John Garnevicus learned how to teach the inertia lab during a professional development workshop for science teachers. During that professional development workshop, the facilitator distributed similar materials—PVC pipes, pulleys, weights—and teachers in the room were split into groups and tasked with solving the problem. John generated the technique that his group ended up using. He then introduced the lab to his Physics class beginning last year.

Last year, John remembers, a Friends student came up with the idea her experiment in just two minutes, faster than any of the Physics teachers in the workshop. She broke the experiment.

During the lab, students design an experiment to find the moment of inertia (the rotational equivalent of mass) of an irregular object (a T-shaped PVC pipe or an apparatus built for this experiment). Everyone is given the same starting point (use a falling mass to spin the object), but had to make choices as to how they would control errors. The challenge is to figure out how to use what they've learned about rotational motion to come up with a solution.

"There are three or four different possible ways to solve it," John said, "but some work better than others. Once you get the experiment set up properly the data gathering is quick, but it does take some time to gather the experiment and set it up."

 

View more photos from the lab at: http://www.friendsseminaryphotos.com/SchoolYearGalleries/20152016-School-Year/Moment-of-Inertia-Physics-Lab