Center of Gravity Trick

A friend sent me an email about a wrecker that fell into the sea trying to recover a car.  Another wrecker was sent to rescure the first.  It also fell into the sea.  Both wrecker drivers had over extended the load on their booms.  They had forgotten the old engineering principle about the center of gravity.  My Dad would show us boys this trick before I ever started Elementery School.  It's one of the most graphic ways I know to teach the principles of how center of gravity works.

Press the tines of a fork onto a spoon.  Slip a toothpick between the fork tines at 90 degrees.  Place the toothpick on the wet rim of a large glass. (Real glass won't burn.  Don't use plastic or other flamables!)


Strike a match and set fire to the end of the toothpick that extends over the glass.


The toothpick will burn down completely until it touches the wet rim of the glass.


It will burn out leaving nothing but the charred edge of the toothpick remaining to hold up the heavy fork and spoon.
It WILL NOT fall because the center of gravity is below and toward the center of the glass.


The part remaining holding things up is no longer than the thickness of the glass.  Notice how the handle of the fork remains "afloat" not touching.  Nothing touches anywhere except the toothpick.  It's not magic, just grade-school science.


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