Always up

Two kinds of force affect the swaying doll: the ground reaction force and the doll's weight located in the centre of gravity. Since both forces are not aligned they interact and as a result of this interaction the unbalanced moment of force makes the doll regain its balance.

The above phenomenon is illustrated by the picture. 'Always-down', is the doll which falls down since its centre of gravity is located high.

'Always-up' remains in the state of permanent balance: it always regains balance as a little ball inside a bigger hemisphere, in contrast to transitory balance in 'Always-down', like a little ball at the top of a bigger hemisphere.

In this way the leaning doll attains the minimal amount of potential gravitation energy; the lower the centre of gravity the lower the potential gravitation energy.