Re: I need an explanation for an experiment I saw invol balance and gravity.

     OK, do you know why balancing it in the first place works? It has to 
do with the "center of gravity." What scientists mean when they talk about 
an object's "center of gravity" is the point can seem to represent where 
the mass of an object is; this means the point where when you push it, it 
just moves, it doesn't twist or slide at all. For example: if you get a 
bar of soap wet and put it on the countertop, and then push it at a 
corner, it will probably slide forward a little but will spin around more; 
but if you push it in the middle, it will slide forward. The center of 
gravity is like that, but in all three dimensions -- so it's like figuring 
out where to push a bar of soap floating in a bathtub.
     Now back to the fork/spoon/toothpick combination (you can also do it 
with two forks and a toothpick stuck into a cork). If you look at the 
shape, you can figure out that the center of gravity has to be in the 
middle somewhere, which is why you can balance it in the first place. Why 
can you burn away the toothpick? Because the position of the center of 
gravity is based on the way mass is distributed in an object. Think of how 
much the toothpick weighs compared to the spoon and fork; so when you get 
rid of some of the toothpick, the center of gravity doesn't really move 
much at all, which is why the combination stays balanced.
      The toothpick stops burning at the glass because the glass acts as 
a "heat sink", which means it won't let the wood in contact with it get 
hot enough to burn unless it heats up the whole glass, which a burning 
toothpick can't do.