PURPOSE: To demonstrate a basic property of the motion of planets or satellites in an inverse square gravitational field.

DESCRIPTION: The surface of this "potential well" is shaped so as to produce an inverse square gravitational force. Giving a small ball a tangential velocity near the outer radius of the well, one can create elliptical orbits which demonstrate conservation of angular momentum as the ball rolls around the well.

SUGGESTIONS: Practice to achieve the best orbits; friction is a bit of a problem, but with a good start several rotations can be achieved. Please flush after use.

REFERENCES: (PIRA 1L10.50) A smaller version of this demonstration is E1-12: MARBLE IN GLASS BOWL. See also film loops "ORBITING BODIES IN VARIOUS FORCE FIELDS, PARTS I AND II.

EQUIPMENT: Potential well with ball.


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