Bathtub Physics  - Density, Buoyancy and Flotation

Russell, Renee South Shore High School
(312) 933-8180

Objectives: Understand Archimedes' Principle, flotation and the reaction of bouyant forces. Explain the relationship between density and flotation. Apparatus needed: triple-beam balance 800ml beaker hooked mass 50g water spring scale bathtub (large container string or pool small) 500-ml graduated cylinder gallon jug salt solutions: Use Epson Salt 1. sea water 3.5g of salt per 100cm3 2. Great Salt Lake 20g of salt per 100cm3 3. Dead Sea 25g of salt per 100cm3 Recommended Strategy: 1. Record the weight of an hooked mass with a spring scale. Fill a graduated cylinder half-full of water and record the level of water. Hang the mass from the spring scale and lower the object until it is submerged in the water in the graduated cylinder. Record the weight of the object in the water and the amount of water displaced. 2. Use a bathtub to find a student's volume. Fill the tub half-full and mark the level. Submerge a student and mark the level of the water. Once the student is out of the tub, use a measuring device- large graduated cylinder, gallon jug - to fill the tub to the higher mark. The amount of water needed to do this will be equal to the students volume. 3. Place an uncooked egg in a 800cm3 beaker half filled with water.
Next place the uncooked egg in each of the containers of salt
solutions one at a time. Make careful observations of what happens in
each solution and record your data.

References Floating - A Key To Survival Science and Children October 1980 33-35.
Conceptual Physics Paul Hewitt
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