PURPOSE: To illustrate buoyancy in a paradoxical way.

DESCRIPTION: A large styrofoam block with a smaller aluminum block mounted on top as in the picture at the left, floats with the center of the styrofoam block, marked by the black line, at the water level. Q: When this gizzit is inverted, with the aluminum block in the water, will the water level be (a) above, (b) below, or (c) at the black line? A: The water level will be below the black line, as seen in the picture at the right.

SUGGESTIONS: Let your students vote on this and discuss it before doing the experiment.

REFERENCES: (PIRA unavailable.)

EQUIPMENT: Styrofoam/aluminum block floater, tank of water.

SETUP TIME: 5 min.

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