PURPOSE: To demonstrate weightlessness in free fall.

DESCRIPTION: A small mass is attached to the inside center of a beaker using a light spring. The cup is held upside down, with the mass hanging out of the cup, then released from rest. Ask the students what will happen when the cup is released: (a) the mass will extend the spring, like a parachute, due to air pressure pulling on the cup, (b) the mass will be pulled up into the cup by the spring, or (c) the cup will fall with the mass in its original position. Click on the photograph above to view the action.

SUGGESTIONS: See Question of the Week #103 for information on using this demonstration to enhance class involvement.

REFERENCES: (PIRA 1G20.40) See Demonstration Reference File for lots of argument regarding this topic.

EQUIPMENT: Teflon beaker with 50 gram mass attached to the bottom by a spring, as photographed.

SETUP TIME: None.