Conservation of angular momentum...see it, feel it, a simple, seat of the pants demonstration
In this group demonstration/experience students feel how angular momentum is generated, learn what angular momentum is, and see how it is conserved when there are changes in the mass distribution. Each student (and the instructor) sit in a chair that spins easily. Another student spins the chair. Each student has the opportunity to observe several other students, and the teacher spin and to be the spinner themselves. As this is going on, the teacher asks for observations and predictions about what is happening, drawing attention to the varying rates of spin and what has contributed to them, such as position of the arms and legs. The demonstration is repeated several times by different experimenters.
- Conservation of angular momentum.
Process of Science Goals
The process of observation, hypothesis, and testing in a non-threatening way, is the real goal of the activity. It also encourages the student to share their thoughts and ideas with others and repeat experiments several times to see if the results are reproducible. I really want them to see how this process is present in many areas of their daily activities.
Context for Use
This is a quick demonstration for a small group of students. The only equipment needed is a chair that spins easily. This activity occurs during the discussion of the laws of motion. It is intended to be a lighthearted and fun experience early in the course. Many students report going home and showing this to family members.
Description and Teaching Materials
A chair that spins easily and a variety of students.
Teaching Notes and Tips
Ask what the students are seeing. Ask how it feels. Ask them to make a prediction about what would happen if the student put his legs or arms out or in. Have them compare what they saw with each others observations. Have them repeat the experiment if there is disagreement or uncertainty about their observations. Encourage them to respect other peoples observations and to make modifications that might influence the results.
If they are making observations, engaging each other and pointing out what is happening, they are getting it. If they are having fun and participating, they are understanding that the process of science can be relevant and do-able in their own daily lives. They are getting that science is not difficult or abstract, and that it isn't a mostly useless bag of tricks and complicated mathematics.
References and Resources