Survive falling into water. Calm vs Disturbed

[WolfieWarband]

I heard that you can not survive a fall into water at a height of 250 feet or higher.
I have also heard that the reason for this is it acts like concrete at the speed you would be traveling.

My example scenario is kinda odd but goes like this. You are a paratrooper. You have just jumped out of a plane and your parachute has failed to deploy but, there is hope because the ocean is under you. If you drop a cooked grenade into the water would it disrupt the water to the point that you could fall into the blast point and survive?

My reasoning:
1.What kills you is the sudden stop. So making the impact last longer (with a roll for example) reduces the chance of death.
2.You would still hit the water but, disturbed water is more spread out with pockets of air so it may slow your fall over time and not all at once. Possibly leading to you being able to survive the fall.

 

[CWatters]

Yes it might work but fragments of the grenade will go in all direction including upwards.

You might be interested in this..
https://www.newscientist.com/article/dn1350-bubbling-seas-can-sink-ships/

Bubbling seas can sink ships

By Joanna Marchant

Lab tests have proved that bubbles can sink floating objects. The findings add weight to suggestions that methane bubbles escaping from methane reserves in the seabed might have been to blame for vessels disappearing in the Bermuda Triangle and the North Sea.

The Greek mathematician Archimedes realized that for something to float, the density of the liquid has to be greater than the density of the object. So a simple argument is that if you mix enough bubbles into a liquid to lower its average density, an object floating on its surface should sink. People have suggested that this process is behind the mysterious demise of many ships that sank for no obvious reason. Continued..

 

[WolfieWarband]

Yes it might work but fragments of the grenade will go in all direction including upwards.

You might be interested in this..
https://www.newscientist.com/article/dn1350-bubbling-seas-can-sink-ships/

That was quick thank you for a great read as well.
Is there a way to tell how much higher that would allow?
Or is there to many unknown variables to figure that out?

 

[anorlunda]

That was quick thank you for a great read as well.
Is there a way to tell how much higher that would allow?
Or is there to many unknown variables to figure that out?

There is no simple yes no answer. Although falls at that height are usually fatal, everyone remembers the notable exceptions. Readers Digest once had a story about a man that fell 20000 feet out of a bomber in WWII and survived. But others have died tripping over their own feet.

 

[A.T.]

man that fell 20000 get out of a bomber in WWII and survived.

Ground or water? I remember reading a case from the pacific, with water impact, bones broken, but still able to swim to nearby shore.

 

[A.T.]

If you drop a cooked grenade...

I would do that every time as a paratrooper, to clean my landing zone.

But seriously, getting the timing right on that one would be the most difficult part. On the other hand you have little to lose here.

 

[anorlunda]

Ground or water?

If I remember right, it was snow.

 

[anorlunda]

But seriously, getting the timing right on that one would be the most difficult part. On the other hand you have little to lose here.

We should have an engineering term for that. I mean the desperate things you try when you have only seconds to live and nothing to lose by trying.
Invent the right phrase and it could go viral and make you famous.

 

[A.T.]

We should have an engineering term for that. I mean the desperate things you try when you have only seconds to live and nothing to lose by trying.

Terminal Creativity

 

[XZ923]

We should have an engineering term for that. I mean the desperate things you try when you have only seconds to live and nothing to lose by trying.
Invent the right phrase and it could go viral and make you famous.

Zugzwang Improvisation

 

[berkeman]

"I'll be back!"

 

[rootone]

When the grenade is dropped it probably won't fall a lot faster than the guy is falling.
Maybe a little faster as it probably is a roundish shape, more aerodynamic, so is less affected by air resistance
But he wants it to fall a LOT faster than him, so that it detonates several seconds ahead of his own arrival at the surface.

 

[berkeman]

When the grenade is dropped it probably won't fall a lot faster than the guy is falling.
Maybe a little faster as it probably is a roundish shape, more aerodynamic, so is less affected by air resistance
But he wants it to fall a LOT faster than him, so that it detonates several seconds ahead of his own arrival at the surface.

Reminds me of a RoadRunner cartoon...

http://home.ku.edu.tr/ffisunoglu/public_html/coyote/wile-coyote-wallpaper.jpg

 

[A.T.]

When the grenade is dropped it probably won't fall a lot faster than the guy is falling.
Maybe a little faster as it probably is a roundish shape, more aerodynamic, so is less affected by air resistance
But he wants it to fall a LOT faster than him, so that it detonates several seconds ahead of his own arrival at the surface.

Yeah, you want to throw it down. But getting the timing right at the first time, including the grenade's detonation delay, is very unlikely. I would rather concentrate on getting the body position right, to minimize damage.

 

[A.T.]

We should have an engineering term for that. I mean the desperate things you try when you have only seconds to live and nothing to lose by trying.

Related Physics Puzzle:

By accident you walk into an elevator shaft, with the elevator at rest somewhere far below you. Before you start to fall you have just enough time to push one of two buttons:
- UP will instantaneously make the elevator move up with a constant speed V
- DOWN will instantaneously make the elevator move down with a constant speed V
What do you do (to minimize your impact speed) ?

Assume no air resistance, and that when pressing DOWN you will reach the elevator before it reaches ground floor.