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Nov18-12, 01:44 PM
P: 11,925
You need an additional mass below the anchor, which acts a bit like a pendulum - if you raise one side, you shift the "pendulum" mass to that side, and get a restoring force in the opposite direction. If both sides are in balance, the stable position is horizontal. If one side is lighter, it goes up until the "pendulum" mass balances this.