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Re: [Phys-l] swimming



What does 'easier' mean here? If it is just recreational swimming, then denser fluid makes it easier to float and therefore requiring less effort to avoid drowning. That seems 'easier' to me. On the other hand, if it is speed in moving from point a to point b in the fluid, then viscosity plays an important part and you have a combination of effects.

Consider two extremes--fresh water and mercury--not that you'd want to swim in mercury. In the mercury less that 10% of your body would be submerged. But if the frictional forces are 10-13 times higher than for water, moving that much smaller cross-sectional area through the mercury would be just as difficult--if not more so. One concern in thinking through this is to not confuse emulsions with regular fluids. Quicksand, for example, is not really a fluid and doesn't act the same--although if one avoids panic, 'floating' in quicksand is not too difficult (think the Mythbusters did this one too).

rwt

***************************
Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, IN
rtarara@saintmarys.edu
******************************
Free Physics Software
New multi-input energy simulator--plays similar to the Montana State analog computer.
www.saintmarys.edu/~rtarara/software.html
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At 9:39 AM -0400 3/30/10, Bob Sciamanda wrote:
> After our discussion, we both figured that it would be easier
to swim in a
more dense liquid, but we could not do an experiment to prove this.

How about fresh water lakes vs oceans or the Great Salt Lake?
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_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l