Hydrostatic Pressure: Radial Inwards vs Outwards

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Discussion Overview

The discussion revolves around the nature of hydrostatic pressure and its directional effects, specifically whether it acts radially inwards or outwards. Participants explore this concept through examples such as divers experiencing pressure underwater and the behavior of water-filled balloons. The conversation includes theoretical considerations and practical implications related to diving and snorkeling.

Discussion Character

  • Exploratory, Debate/contested, Conceptual clarification

Main Points Raised

  • Some participants assert that hydrostatic pressure is exerted in all directions, questioning what determines its radial directionality.
  • One participant claims that divers do not experience a crushing sensation, suggesting that the sensation is exaggerated.
  • Another participant explains that if the pressure inside an object is greater than outside, the net force will act outwards, while if the outside pressure is greater, the net force will act inwards.
  • There is a discussion about the pressure experienced by divers, with one participant suggesting that at greater depths, divers feel a sense of being squeezed, which may limit their ability to breathe.
  • Some participants clarify the differences between snorkeling and scuba diving, noting that the pressures involved in each scenario affect breathing differently.
  • Questions are raised about the pressure on submerged objects in a jug of water, with a focus on whether the walls of the jug exert greater pressure than the fluid itself.

Areas of Agreement / Disagreement

Participants express differing views on the sensations experienced by divers and the implications of pressure in various scenarios. There is no consensus on the nature of the sensations felt by divers or the specific mechanics of pressure in relation to snorkeling versus scuba diving.

Contextual Notes

Some assumptions about pressure dynamics and the experiences of divers may not be fully explored, and the discussion reflects varying interpretations of pressure effects in different contexts.

Freddy86
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Hydrostatic pressure is exerted in all directions but what determines whether it acts radially inwards or radially outwards. For example, if you are a diver you feel pressure from the water acting inwards, giving you a crushing sensation. However, if you fill a balloon full of water and poke holes in it, the pressure acts radially outwards?
 
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Divers do not get a crushing sensation. That would be awful and no one would want to do it!

The pressure pushes a balloon out because there is a higher pressure inside than outside.
 
If the pressure is larger inside, the net force will be outwards. If the pressure is larger outside, the net force will be inwards. In the case of a diver the forces are equal (just about) with no net force.
 
russ_watters said:
Divers do not get a crushing sensation. That would be awful and no one would want to do it!

The pressure pushes a balloon out because there is a higher pressure inside than outside.


Thanks for the replies. So if you submerge an object in a jug of water then the pressure will be radially inwards on this object right? Is this because the walls of the jug are considered to be at greater pressure than the fluid then?

No I meant that if a diver went down too deep they get a sense of being squeezed (maybe crush is too drastic). I thought this was why the depth of snorkeling is limited as the deeper you go the more your chest gets squeezed so at a particular depth you cannot expand your diaphragm anymore and are thus are unable to breath.
 
You cannot snorkel very deep because you breath out of the air above which is indeed at a lower pressure, but you can scuba because then you breath out of a pressurized container. You didn't specify which one you're talking about.
 
Freddy86 said:
Thanks for the replies. So if you submerge an object in a jug of water then the pressure will be radially inwards on this object right? Is this because the walls of the jug are considered to be at greater pressure than the fluid then?
The walls will constrain the liquid, yes - otherwise it would break and all the water would pour out.
No I meant that if a diver went down too deep they get a sense of being squeezed (maybe crush is too drastic). I thought this was why the depth of snorkeling is limited as the deeper you go the more your chest gets squeezed so at a particular depth you cannot expand your diaphragm anymore and are thus are unable to breath.
"Diving" typically means scuba diving. It isn't the same as snorkeling. dauto is right; for snorkeling, you have to fight the water pressure to breathe (as does your snorkel - if it isn't rigid it will collapse). But for scuba diving, you don't.
 

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