Buoyancy

First I guess we should find out what exactly buoyancy is. That wasn't easy. Let's visit BrainPOP, http://www.brainpop.com/science/forces/b... . It has a movie. This site is slow to load but worth the wait. There are two forces acting on an object submerged in a fluid - gravity (pulling it downward) and an upward force trying to float it. The upward force is the buoyant force, which is equal in magnitude to the weight of the fluid displaced by the object. How can you determine if an object will float or sink? Take an object and immerse it in a fluid. The volume of fluid that the object displaces is equal to the volume of the object itself. The object will float if it weighs less than an equal volume of fluid. It has positive buoyancy. If the object weighs more than an equal volume of the fluid, it will sink. It has negative buoyancy. If the object weighs the same as an equal volume of fluid, it neither sinks nor floats but drifts within the fluid. In this case, the object has neutral buoyancy. A floating object displaces it own weight in fluid. One can look at this in terms of density (mass/volume). If the density of an object is less than the density of the fluid, it will float. This determines the level at which an object floats. Heavier or denser objects sink lower than lighter (less dense) objects ( http://webspinners.com/dlblanc/tectonic/... ). To see the relationship between buoyancy, mass, weight and various fluids, try playing around with the buoyancy simulator, http://wigner.byu.edu/Buoyancy/buoyancy.... .

The first person to investigate buoyancy was Archimedes, a Greek mathematician who lived from 287-212 B.C ( http://www-groups.dcs.st-andrews.ac.uk/~... , http://www.mcs.drexel.edu/~crorres/Archi... ).

Now, how about having some fun? Surf over to The Space Science Group at Northwestern State University Natchitoches, Louisiana, http://www.spacesciencegroup.nsula.edu/s... . This is a great site! There is an explanation of the phenomenon being discussed. At the bottom of the page is a surfing section listing other web sites of interest. Browse through the lab activities. Simulate a diver using a bottle of water and a ketchup packet. Find out why when you place a can of regular pop and a can of diet pop in a bucket of water, one sinks and the other floats.

Now pop over to Nova Online, http://www.pbs.org/wgbh/nova/lasalle/buo... . After reading Buoyancy Basics try your hand at the Buoyance Brainteasers. The questions are well done and will make you think.

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