Mechanics > Newton's Laws > Inertia

DCS# 1F20.40

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BROOMSTICK AND WINE GLASSES

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APPARATUS

two 5/8" x 4' pine dowels	202-14-B
two wine glasses, beakers or pop cans	202-14-C
metal rod	202-03-E
pins	202-14-C
several pairs of safety glasses	013B-02-B

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DESCRIPTION

A broomstick is supported on the rims of two wine glasses by the pins inserted in each end.  When struck with the metal rod, the broomstick should break and fall without disturbing the wine glasses.  You can follow up by showing what happens if you simply press down slowly on the dowel, using the second dowel.

 NOTES

 

Hammer pins into the ends of the dowel, then remove the heads with wire cutters.  Without the pins, there are more ways that things can go awry - you need to strike the dowel at its center and with no horizontal component.

Mark the center of the dowel.  Score it all the way around to discourage splintering. 

Set the glasses at the very edges of the tables so that if the wood doesn't break, the pins simply bend and the dowel clears the tables.  Taping the glasses in place will help to protect them from after-effects.

Practice with pop cans.

REFERENCE

 TPT 31, 230 (1993).