Equipment:

• conical pendulum - shelf 5A
• table clamp, clamp - hall cabinet
• support rod - bucket beside hall cabinet
• two 200 g masses - shelf 4D
• billiard ball with hook - ball drawer
• string

Theory: An object experiencing uniform circular motion must have an unbalanced force acting on it, directed toward the center of the circular path.

Description: The billiard ball has a mass of about 200 g, so it is balanced by one of the hooked 200 g masses. When the second 200 g is hooked to the first, the masses drop to the table and the ball is pulled to the top of the conical pendulum - clearly the ball is incapable of balancing the 400 g mass. When the ball is set into circular motion, however, it will balance the 400 g mass.

Setup time: 10 minutes

References: (available in the demo room)

• Sutton, "Demonstration Experiments in Physics", M-138, p. 61.

Other demonstrations in this category : Ball on a string 1D50.10 -- Carnival ride model 1D50.30 -- Pail of water 1D50.40 -- Penny on a coathanger 1D50.45 -- Rolling chain 1D50.70

Previous category : Motion of the center of mass - Meter stick with 3 lights 1D40.10

Next category : Deformation by central forces - Flattening earth 1D52.10