Falling into a body of water from a great height (or at a high speed) is the same as hitting concrete. (Many variations)
Clearly this is not true. However, the following may be true:
Falling from height x into water is essentially the same landing on concrete from height x because the end result (your death) is the same.
What is height x?
or…
What is the LD-50 velocity for hitting the surface of a body of fresh water for the average human? salt water? (Assume that the falling body does not smash into the bottom of the body of water.) How does this velocity compare to the average terminal velocity? This has bothered me for a long time.
All these are appropriately general questions in my opinion. Now I’ll ask a personal question:
Who wants to volunteer for an experiment? (Volunteers must be free of acrophobia)
Postscript: For all calculations above, assume that the body of water is not frozen.
[QUOTE]
*Originally posted by Lance Turbo *
**From the ‘stuff everybody knows’ files:
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I would opine that it depends on the person and their body position when they hit. I have heard stories about people hitting the water at terminal velocity and living, but these may be stories someone made up to get SEALS to jump out of perfectly good airplanes. I don’t see how you could derive an LD-50 from the available information.
**
That leaves me out then. I’m afraid of spiders!
Hitting a frozen lake would certainly cause deceleration sickness.
“Like an overripe beefsteak tomato rimmed with cottage cheese, the corpulent remains of Santa Claus lay dead on Lake Erie.” (Lytton-Bulwar)
I do not know the math although it was done many years (I won’t say how many) by my high school physics teacher. What I DO remember is this.
Surface tension of water is quite strong. Among liquids generally found in nature (basically not a concoction whipped together in a lab) I think only Mercury surpasses water in this regard. There is a coefficient that describes this property for all liquids.
At the right speed and angle hitting water CAN pretty much be the same as hitting concrete. The effect only lasts a very short moment but that’s when the damage happens. It’s this effect that kills most people who jump off of bridges (ala the Golden Gate) to commit suicide.
Water is hard if you don’t hit it right. I once shot a .58 caliber lead ball (from a black powder muzzleloader) into a creek…the ball hit the water, flattened out to about 3 inches in diameter, and richoted (sp?) up to cut a ~2.5" limb off an oak tree. Yipe.
I think the problem with landing in water is simply its incompressibility–at any reasonable pressure and temperature water is hardly compressible. If you’re just diving into it regularly, you’ve moving slowly enough that its liquidity lets it move out of the way; however, if you smack into it at 150 mph the damage will be done in a fraction of a second, just as if you hit something “harder”.
I’ve heard that the limit for surviving a fall into water is only 60 ft (about 6 stories). To survive a fall from above 60ft depends entirely on how you hit the water:
best way: feet first, toes pointed down like a ballet dancer
not so good way: head first like an Olympic diver
worst: a belly flop or landing on your side => instant death
I once heard about a Russian pilot who bailed out of his Mig without a parachute into the ocean. He supposedly fell many thousands of feet and somehow survived.
According to the 1991 Guinness Book of World Records:
World record high dive: 176ft 10 inches
Highest dive ever survived: Col. Harry A. Froboess jumped 360 ft. into the Bodensee from the airship Graf Hindenburg on June 22, 1936.
Of the 696 people known to have made a 240ft. suicide dive off the Golden Gate Bridge (1937 to 1991) only 12 have survived and only one was able to swim ashore unaided.
From some skydiving page I learned that terminal velocity for a human is about 174fps. (53m/s or 118 mph)
People jumping off the Golden Gate Bridge hit the water at about 38m/s, and occaisionally survive. Of course, only 12 out of 696 survived, but you must bear in mind that most of these people were making no effort to survive the jump. Col. Harry A. Froboess (see above) hit the water at around 46m/s. (Probably slightly slower. I’m assuming that the drop off in acceleration happens pretty quickly as you get close to terminal velocity) This is damn close to terminal velocity. Then there are stories they tell SEALs and Russian fighter pilots.
Based on this evidence, I am going to say that it is possible for a person to survive a fall from any height into a deep body of water. The same can not be said of concrete. Anybody got a problem with that? Anybody want to volunteer for an experiment?
Send resume to:
splat@westroad.com
Subjects of the experiment will be required to rigidly abide the law of gravity. Subjects will not be drug tested. In fact, use of recreational chemicals is encourafed and possibly neccessary if this experiment is to be successful.
