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Example of a stable and an unstable equilibrium, respectively.
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Stability

When someone pushes you on a swing, do you keep going in the same direction or do you swing back the other way? If it wasn't a really strong push, you come back. That's because a swingset is a stable system. That means if you don't do anything after you get pushed then you will return to where you started. If the swingset was unstable then you would keep going with just a little push and not end up where you started.

The atmosphere can be either stable or unstable. If it's unstable then clouds can form. If it's really unstable then a lot of clouds can form and turn into a storm and then begin to rain.
Last modified May 26, 2004 by Jennifer Bergman.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF