Strange but true for March 8 3/8/2009 12:31 AM By BILL SONES and RICH SONES, Ph.D. Columnists
Q. Bad luck: Your plane's out of fuel and is going down. Worse, your parachute pack fell out just seconds ago and is free-falling toward Earth. Have you got a prayer?
A. Barely a prayer, and better make it a fast one, then leap for your life, says the University of Virginia's Louis A. Bloomfield in "How Things Work: The Physics of Everyday Life."
Suppose the pack's been falling 30 seconds. It should already be at terminal velocity, maybe 100 mph, where its downward weight is offset by air drag and no further acceleration occurs. You're much heavier and denser so your terminal velocity - attained within several seconds - will be greater, depending on your weight and body positioning.
Draw yourself up into a human cannonball or dive head first and you can minimize drag and maybe reach 200 mph, thus gaining on your pack at a relative 100 mph.
Still, you'll need time to catch up. How high are you?
With the pack nearly a mile down, you'll catch up in about 30 seconds, during which you'll drop a mile and two-thirds. Now a moment more to put on the pack and deploy the chute, then time for it to slow you down.
Bottom line: If the plane was up over 2.5 miles, you just might make it.
Q. Why do dogs make such great pets?
A. Tens of thousands of years ago, wild dogs - wolves, really - hung out around campsites, feeding on scraps and barking out warning of approaching strangers in return, says Guy Murchie in "The Seven Mysteries of Life." Later, "domesticated" dogs joined humans in the hunt, serving as finders, retrievers, protectors and companions.
Today, by the tens of millions, we two species live under the same roof - warp and woof! Fundamentally, our mental makeups mesh. As wolf-descendants, dogs are pack animals with complicated social patterns, facial signals and a strong hierarchy of dominance and submission, says Juliet Clutton-Brock in "A Natural History of Domesticated Mammals." Adopt a dog and you become pack "leader."
Out of the complex give-and-take of underdog living with top-dogs there grows an empathy so close that a puppy in a smile-a-lot family "will actually mimic this expression by a sideways grin of the lips and muscles around the mouth."
Now hundreds of generations of selective breeding for puppylike features such as tractability, floppy ears and play, while screening out fear of strangers and unfamiliar situations, have remade dogs closer to our heart's desire - or desires, as 400 to 800 different breeds attest.
"No wonder dogs seem so perfectly matched to humanity's requirements and so perfectly adapted to our lives," says Stanley Coren in "The Intelligence of Dogs." "We created them to be so."
Q. Don't try this, but could you lift a person by the hair? Wouldn't the strands tear or pull out of the scalp?
A. "I've seen Chinese circus performers do this," says Kevin J. McElwee Ph.D., of Philipp University Department of Dermatology, Marburg, Germany. Healthy hair is strong, about equivalent to copper wire of the same diameter.
So the question is how well are the hairs anchored in the scalp skin, not much studied. But chest hairs have been tested to hold roughly 70 grams each.
Assuming head hair to be similarly rooted, and multiplying 70g by 80,000-120,000 scalp hairs per person, the math works out to 12,000-20,000 pounds hanging force!
In reality, the max would be less, due to imperfect fibers, weathering defects, etc., but still plenty of anchoring strength overall to lift a person by the hair-and several others besides."
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