If you jump off a bridge 50m above the water does the water need to be 50m deep?

[tony873004]

It's a visual thing...

Maybe I'm wrong then about the surface tension being broken by bubbles or choppy water or whatever.

 

[rcgldr]

Maybe I'm wrong then about the surface tension being broken by bubbles or choppy water or whatever.

I don't thing surface tension is a big factor. As another factor, it would take a tremendous amount of bubbles to reduce the effective density, as mentioned in another discussion regarding if a boat's water line would be affected by going over a bubbly section of water. I wonder if diving inside the water of a water fall would help (like the cases of barrels over Niagra Falls).

 

[tony873004]

Here's a link confirming what you said about spraying water:
http://juniorengineering.usu.edu/workshops/water/water.php

Another way to reduce surface tension is through physical means. If you have ever done a belly flop off the diving board you should be quite familiar with how water's surface tension effected you. Platform divers feel the same sting even when they land properly. To help reduce surface tension, a hose with a nozzle is positioned to spray water into the pool at the spot where the diver enters the water.

 

[tony873004]

... as mentioned in another discussion regarding if a boat's water line would be affected by going over a bubbly section of water. I wonder if diving inside the water of a water fall would help (like the cases of barrels over Niagra Falls).

I saw a Discovery Channel, or maybe it was Nova episode on why large ships sink, and one theory was giant bubbles that altered the water's buoyancy.

Re: Niagra Falls, I would imagine it would have to help. Is the surface even clearly defined at the bottom of a waterfall? There's got to be a reason the barrel riders choose Niagra, rather than a tall cliff into a lake.

 

[Loren Booda]

Bubbles of methane?

 

[rewebster]

methane?


you don't mean 'landfill' or 'ocean/river' bottom methane, do you?

 

[Loren Booda]

I heard (must have been on the Discovery Channel) a theory that ships in the Bermuda triangle were sunk by large outgassing of methane due to an underwater landslide. Maybe "ocean bottom" methane.

 

[tony873004]

Actually, this was an easy Google ("bubbles of methane sink ships"):

http://www.abc.net.au/science/news/stories/s973492.htm
http://www.newscientist.com/article/dn1350.html

 

[Loren Booda]

Oct. 2007 Physics Today happens to have a related article (not about sinking ships, but gas storage) "Clathrate hydrates under pressure."

 

[rewebster]

I heard (must have been on the Discovery Channel) a theory that ships in the Bermuda triangle were sunk by large outgassing of methane due to an underwater landslide. Maybe "ocean bottom" methane.

ahhhh, it's from all those bean-eating Atlanteans still living down there---

 

[JimmyJockstrap]

If i drop a rock off this bridge approximately how long should it take to hit the water if it is 10-15m below?

 

[rbj]

If i drop a rock off this bridge approximately how long should it take to hit the water if it is 10-15m below?

you got to do your physics. do you know what the relevant equations are?

like

d = \frac{1}{2}a t^2