Jumping into water from a height

[reiver33]

How deep would a fish pond have to be to cushion someone jumping from a first-floor balcony. The rooms have high ceilings, so say 12 feet, plus a little for the balcony - maybe 15 feet in total?

Ideally he would be able to land while retaining hold of the unconscious woman in his arms, but he could release her to spash-down seperately if need be.

Cheers!

Martin

[Alex, The G and T]

Oh, this is my kind of question. One of my favorite pastimes is hurling myself off of precipices into deep water.

Well, a key point there is "deep."

however...

Speaking from experience... A ca. fifteen foot drop into into 5 or 6 feet of water: Land butt first, prone enough to increase drag, increasing proneness, on impact, guaging that fine line between a raspberry flop and too much slipstreaming. You will touch the bottom. (Do not enter feet, or head first.)

Less than five feet of water is going to get painful. I reckon that less than 4 feet of water yields a high probability of debilitating injury.

(All assuming a reasonably smooth bottom. An odd, misplaced stone will ruin your day.)

[reiver33]

Hurrah!

That would be OK for him, assuming he knows, or is lucky enough, to land in the correct fashion. If he can't risk letting the unconscious woman land willy-nilly then he'd have to keep her in his arms, increasing the weight factor of a combinded splash-down.

Any idea how much deeper, assuming average weights?

[Alex, The G and T]

Actually, since my last post, I was pondering the effect of a second body. If the hero had the victim perpendicular across his lap, and they both landed x shaped and relatively flat; the surface area of body hitting the water, thus the rate of deceleration would be similar. If they are clasped belly to belly, they will pass through more water, faster.

In either case weight isn't significant. The factor is speed developed falling in the air at 32 feet per second per second acceleration. (reference Gallileo dropping cannon balls off of the tower at Pisa)

But then I envision some sort of double-bounce-backlash when these kids bounce off the bottom of the pond. Not sure how that would work. Never tried it. };-}

Anyway, 4 to 5 feet depth of water is comfortably plausible for storytelling.

[reiver33]

Whereas the speed at which he/they fall is constant, I remember (going back a few decades) that momentum is based on speed and mass. Hence the greater depth to which a body will penetrate the water before drag slows it down.

[Ursa major]

Given the need to be carrying someone else, this link will probably not help in this specific case, but anyway....

[Bowler1]

BELLY FLOP!!.....SPLASH......

Sorry, could not help myself.

[David Evil Overlord]

Originally Posted by reiver33

How deep would a fish pond have to be to cushion someone jumping from a first-floor balcony. The rooms have high ceilings, so say 12 feet, plus a little for the balcony - maybe 15 feet in total?

Ideally he would be able to land while retaining hold of the unconscious woman in his arms, but he could release her to spash-down seperately if need be.

Cheers!

Martin

Yes, Mr. Bond. Leap into the fish pond. Pay no attention to the decorative piranha. Bbwahahahahahahahahahaha!!!

[Gumboot]

From a fall of 15ft you're going to reach a speed of ~34km/h which is plenty enough to be fatal, depending what and how you impact. The safest way to land in water is feet-first, however this increases the depth you'll need, so for a pond it's not really an option (you might as well land directly on the ground).

In contrast, if you land spread-eagle or any other spread-out way you're going to feel the impact all that much more, because you have to displace so much more water at the moment of impact. This is even worse if you're carrying someone else, because you basically have double the momentum (assuming two people the same mass) so it takes twice as much work to bring you to a stop.

I would say no matter how you land a 15ft fall into 5ft of water by a person carrying another person is going to result in injury. and bear in mind that 5ft is extremely deep for a "fish pond".

[Vertigo]

Don't know how to do those YouTube link thingies but here is a video of Ursa's "Mr Splash" an American stunt diver diving from 36 feet into 12 inches of water. Note he does know exactly what he is doing which makes a big difference. Pretty wild all the same.

http://www.youtube.com/watch?v=JINC4...eature=related