Example of a stable and an unstable equilibrium, respectively.
Click on image for full size
Have you ever tried to balance a long stick on your hand? Hard, isn't
it? That's because the stick is part of an unstable
system. If the wind pushes the stick a little bit, it will keep going in
that direction. If you hold the stick upside-down it's much easier to
keep straight. That's because when the stick is held from above it's a
system. If a breeze moves the stick, it will
come back to its starting position.
The atmosphere can also be stable or unstable. If it's unstable, then clouds
can form. The
more unstable the atmosphere is, the more severe
the weather could
be. Clouds and storms form when pockets of air rise and cool. The air
pockets won't rise unless something starts them moving. That's why the
air can be unstable but still clear--there's no lifting
to get the air going.
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