Question:
Why is it easier to maintain your balance while gliding on one
ice-skate then while standing still on one ice-skate?
Replies:
This is essentially the same as the reason why it is a lot easier
to keep your balance on a moving bicycle than on a stationary one. The point
of contact with the ground in both cases is well below the center of mass.
That means that, when moving, there is a net angular momentum about that
"pivot" point. If you are slightly off balance, your center of mass is not
directly over the pivot point, but to one side of it. Then the force of
gravity starts pulling you down, but because of the angular momentum (just
like with a gyroscope) this gets changed into a turning motion - you change
direction a little by leaning to one side or the other, and if you keep
leaning in the same direction you will go around in circles. Of course there
is some point (you lean too far, or slow down too much) where gravity wins out
and you just fall over. But the faster you are going, the more stable you
will be.
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