by piglover

Created on: May 27, 2009

Actually, pulling a tablecloth out from under a table setting is not really a trick at all. It is a simple law of motion. An object in motion remains in motion. An object at rest remains at rest. The dishes in the table setting are not moving. They will remain in their state of not moving unless a force is directly applied to them. The only real trick is that once you start to move that tablecloth, you better keep on moving it with even and constant motion or you will have an expensive and unimpressive mess to clean. I have done this one for my students. It amazes them every time until I teach them the law of motion. I let them try. Once they get the hang of it, it is still impressive. The impressive feeling just switches from me to them.

You can actually show the same "trick" with an empty water bottle, a piece of index card and a nickel. Cut a small piece of index card and place it over the top of the empty water bottle. Set a nickel on top of the index card. The nickel is at rest and will not move unless the force is directly applied to the nickel. Now, flick the index card with your index finger or ring finger. If done with a constant motion, the index card will fly and the nickel will drop into the empty bottle. No force has been applied to the nickel. It simply does not have its resting place available when the index card is moved. This one is really a blast for kids to play. My students usually want to prove this one over and over again.

Another one that amazes them needs to be done outside unless you are really sure of your ability to have constant motion. Fill a bucket with water. The bucket needs to have a handle. Slowly swing the bucket of water back and forth. Gradually increase the swings until you swing the bucket all the way around in a complete circle. If you have the constant motion part down well, not a drop of the water will spill. If you do not have the constant motion part down well, you get a free bath and amuse everyone around you. This is most fun with younger kids. They usually can't get the constant motion thing down. It is best done on a nice warm day with a child who has friendly parents. It is most helpful if these parents enjoy a good joke and have dry clothes available for the little tyke.

These are some simple, but interesting, ways to show a law of motion. It's all in the motion and keeping it constant without applying any force to the objects you wish to remain at rest. It seems very mysterious to those that do not understand. For the most amusement, don't let them in on the secret unless absolutely necessary. Then, you will seem even more amazing.

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