Re: Swim In Water Or Syrup, Human Speed Is the Same

From: firstjois (firstjoisyike_at_hotmail.com)
Date: 09/28/04 

Date: Tue, 28 Sep 2004 00:36:32 -0400

Rich Travsky wrote:
>> http://www.nature.com/news/2004/040920/full/040920-2.html
>>
>> It's a question that has taxed generations of the finest minds in
>> physics: do humans swim slower in syrup than in water? And since
>> you ask, the answer's no. Scientists have filled a swimming pool
>> with a syrupy mixture and proved it.
>>
>> "What appealed was the bizarreness of the idea," says Edward
>> Cussler of the University of Minnesota, Minneapolis, who led the
>> experiment. It's a question that also fascinated his student Brian
>> Gettelfinger, a competitive swimmer who narrowly missed out on a
>> place at this summer's Olympic Games in Athens.
>>
>> Cussler and Gettelfinger took more than 300 kilograms of guar gum,
>> an edible thickening agent found in salad dressings, ice cream and
>> shampoo, and dumped it into a 25-metre swimming pool, creating a
>> gloopy liquid twice as thick as water. "It looked like snot," says
>> Cussler.
>>
>> The pair then asked 16 volunteers, a mix of both competitive and
>> recreational swimmers, to swim in a regular pool and in the guar
>> syrup. Whatever strokes they used, the swimmers' times differed by
>> no more than 4%, with neither water nor syrup producing consistently
>> faster times, the researchers report in the American Institute of
>> Chemical Engineers Journal.
>> ...
>> But while it might sound like a trivial question, the principle is
>> actually fundamental. Isaac Newton and his contemporary Christiaan
>> Huygens argued the toss over it back in the 17th century while
>> Newton was writing his Principia Mathematica, which sets out many
>> of the laws of physics. Newton thought that an object's speed
>> through a fluid would depend on its viscosity, whereas Huygens
>> thought it would not. In the end, Newton included both versions in
>> his text.
>>
>> Hamstrung by their lack of access to guar gum or competitive
>> swimmers, Newton's and Huygens' work was mainly theoretical.
>> Cussler's demonstration shows that Huygens was right, at least for
>> human-sized projectiles.
>>
>> The reason, explains Cussler, is that while you experience more
>> "viscous drag" (basically friction from your movement through the
>> fluid) as the water gets thicker, you generate more forwards force
>> from every stroke. The two effects cancel each other out.
>>
>> That's not always the case. Below a certain threshold of speed and
>> size, viscous drag becomes the dominant force, making gloopy fluids
>> are more difficult to swim through. Had Cussler done his experiment
>> on swimming bacteria instead of humans, he would have recorded much
>> slower times in syrup than in water.
>>
>> But for humans, speed depends not on what you swim in, but on what
>> shape you are. Once the effects on thrust and friction have been
>> cancelled out, the predominant force that remains is 'form drag'.
>> This is due to the frontal area presented by a body - try running
>> with a large newspaper held in front of you and see how much more
>> difficult it is.
>>
>> So the perfect swimmer, whether in water or syrup, has powerful
>> muscles but a narrow frontal profile. "The best swimmer should have
>> the body of a snake and the arms of a gorilla," recommends Cussler.
>>
>> Obviously, just because we can swim doesn't mean we're built for it
>> - and apparently far from it.

Shouldn't they have shaved the swimmers first?

Jois