A question about falling into water

  • Thread starter FuryX21
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Why is it that if you drop into water from a low point you are unhurt, but if you drop from a very high height you die? Or is this just a movie gimmick? This is a question I've been wanting to know the answer to for a long time.
 
Because you can't fall on something at 120 MPH and expect it to be a soothing feeling. I'd say anything over 50 feet is going to hurt a little bit.

I jumped off a 35-40 foot bridge and it didn't really hurt. Of course, I didn't do a belly flop.
 
Because the water doesn't 'yield' as easily when you have a high velocity falling into it. It's not really about the height, but more about the velocity at which you hit the water.

Like Darin already stated, at 50 mph, water literally feels like concrete when you hit it. If you do a belleyflop when you go in, it will H-U-R-T.
 
From what I heard, if you do a belly-flop at 50 mph or over, and then hitting the water. It could break your ribs or possibly other bones.
 
Originally posted by Darin
You hit water at 50, its gonna feel like concrete. But that depends how you go in.

I was saying jumping from a platform fifty feet above the water. At 50 MPH, you're dead I bet.
 
It's got to do with aerodynamics & fluid movement, etc. The fact of the matter is that water can only move so fast to get out of your way when you enter it. The more distance it has to move to get out of your way, the harder it's going to be to move in it. Now, when you enter from the side of a pool, you're only going about 5-10 MPH and the water has plenty of time to move out of the way. However, if you were to hit water from a plane, you'd be going approximately 120 MPH and the water would have alot less time to move out of your way (virtually none, which is why it seems to be hard as rock; because it can't move out of the way to accomodate your moving downward). Do you follow that?
 
Go up to a concrete wall and push it with your finger: You wont get hurt.

Go up to the same concrete wall and punch it: You wont be asking dumb questions again.
 
i saw this on that tv show that used to be on after fear factor. i dont remember what it was called... but anyways they were saying that you just jump in feet first, keep your hands tucked in and pointed, point your toes and keep your feet together... and you should be ok, if you dont hit the bottom.
 
That, theoretically, is correct. Reduce the amount of distance the water has to move; reduce the risk of injury to yourself. The only thing is that you may break your toes (if you're going out of a plane).
 
and have a damn long way to swim back up, because you will sink along way down
 
As an additional bit of information, water is four times denser than air.


As an additional additional bit of information, the "soldier dive" (toes first, arms flat to body) is the best way to enter water at high speed, but you should instantly spread your legs and arms as soon as you're submereged to aid deceleration in the water - or else risk hitting the bottom.
 
I will try to shine some light on this.

The problem is that the water as a medium can't compress or decompress, like air. It has to go somewhere whe you hit the surface. That in combination with the waters internal friction and inertia makes it like a concrete wall at high speeds.

[edit] but that was pretty much what Jpec said..

Famine, I thought that water was about 1.000 times denser than air?
 
Originally posted by Famine
...but you should instantly spread your legs and arms as soon as you're submereged to aid deceleration in the water - or else risk hitting the bottom.

Wouldn't it be better to make a sitting position with your arms out?
 
Originally posted by Jpec07
It's got to do with aerodynamics & fluid movement, etc.

:dopey: Ok here's how you get the aero ,
go to some road work site get you a big orange cone . With me so far? :nervous: Now tape it to your head find a bridge about 50 feet over water. Jump in head first:eek: .After hitting the water turn your head and open your mouth really wide to slow down so you dont crash into the bottom:odd: :odd:

And GOOD LUCK:cheers:
 
Originally posted by GTJugend
Famine, I thought that water was about 1.000 times denser than air?

It's roughly 4 times denser. Really.
 
jumping off of a 40 foot bridge...:odd:

the only time i "jump" into a pool of water is when i "slip" and fall into a pool.

somebody jumping off of a 40 foot bridge and landing flat on their ass is pure crazy:eek::lol:
 
Originally posted by Klostrophobic
Because you can't fall on something at 120 MPH and expect it to be a soothing feeling. I'd say anything over 50 feet is going to hurt a little bit.

I jumped off a 35-40 foot bridge and it didn't really hurt. Of course, I didn't do a belly flop.
anything over 15 ft hurts unless you go in reasonably straight. its to do with surface tension and stuff. No wait, think of it this way if someone hits you with 50 lbs of force it'll hurt but if someone puts there hand on your arm and pushes you with 50 lbs its fine.
 
Originally posted by Darin
From what I heard, if you do a belly-flop at 50 mph or over, and then hitting the water. It could break your ribs or possibly other bones.
The best martial artists punch a 40-50 mp/h at best, go figure.
 
Originally posted by DoZeRxXx
i saw this on that tv show that used to be on after fear factor. i dont remember what it was called... but anyways they were saying that you just jump in feet first, keep your hands tucked in and pointed, point your toes and keep your feet together... and you should be ok, if you dont hit the bottom.


yeah, you have to break the surface tension of the water by diving in like a 'pin'

as my science teacher told me.
 
Originally posted by Klostrophobic
Yeah, it's quite a rush to jump 40 feet down into a body of water. I wouldn't suggest landing on anything but your feet, though.

i could never will myself to jump any amount of feet down into a body of water, and if i did, i would probably be so freaked out, i would land on my ass:lol:
 
Originally posted by Famine
As an additional bit of information, water is four times denser than air.


As an additional additional bit of information, the "soldier dive" (toes first, arms flat to body) is the best way to enter water at high speed, but you should instantly spread your legs and arms as soon as you're submereged to aid deceleration in the water - or else risk hitting the bottom.


If you are going in at speed, you MUST NOT spread your arms and legs. The water rushing past will do alot of damage. Cliff divers use the technique you just mentioned but always hold their legs together as tight as they can. I saw on tv one guy couldn't hold it. His leg was pulled up and dislocated it from his hip. OUCH!!
 
Guiness Book Records for regular (head first) diving is 115 ft, and they have to leap 30 ft horizontally to avoid the rocks :eek: also have to watch the head angle, because face first you'll end up blind....

extreme sport indeed! :D

anybody knows the highest dive feet first?
 
Because of what they all said, the molecules have to get out of your way.

Think of it like this, you're driving in a car going 60 miles per hour. You stick your hand out and feel the air getting out of the way of your hand. You don't feel that when you put your hand out at 2 miles per hour because the air has more time to get out of your way. Air is also more compressible and less dense than water, so you feel the effects of it rushing out of your way less.

You could also think of it like this.

If you want to occupy a space, you have to move what is in that space out of the way. How do you do that? Force.

F=ma. To move water out of the way slowly, a is small so force is small. To move it out of the way quickly, a is large so the force is large.

For every action there is an equal and opposite reaction. The water imparts the force that you exert on it, back on you. The result is you get a large whack (that's scientific).

By pointing your toes and going in straight, you reduce your effective surface area and reduce the amount of mass that you're accelerating at any given time, changing the only other componenet of the equation, m.

ok?
 
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