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I can still remember one of the few practical demonstrations I observed in my first year university physics class many years ago. This illustrated conservation of momentum. It involved our lecturer climbing on to the lecture room bench and standing on a plank of wood resting on (empty) beer bottles laid on their side (to reduce friction).

When he jumped forward by a small distance, the plank of wood shot back by a larger distance (conserving momentum). It was a risky experiment and several beer bottles broke.

I am not sure how many students appreciated the physical law being demonstrated. Practical demonstrations were not common in teaching those days. I suspect for many it just reinforced in their minds that this particular lecturer was, if not mad, at least eccentric.

In these more enlightened day I hope teachers use every advantage to practically demonstrate physical laws. Some of the videos being recorded on the International Space Station ISS could be useful for this.

Last week Astronaut Jeff Williams demonstrated the acceleration experienced inside the cabin during a planned ISS reboost. The ISS is reboosted periodically to maintain its orbit, and to prepare for visiting spacecraft, such as the space shuttle (a launch planned this week) and Progress vehicles.

Jeff’s experiment demonstrates that objects will continue in motion unless acted on by a force. In this case he shows that a free-floating body will move relative to the station when the station is accelerating.

A simple demonstration of an important physical law.

via YouTube – Space Station Reboost.

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