Archimedes principle with a completely submerged ball

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Discussion Overview

The discussion revolves around Archimedes' principle, specifically focusing on the behavior of a completely submerged ball and the effects of pressure in a fluid. Participants explore the implications of pressure differences on submerged objects and question the conditions under which they remain submerged.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant, Dasky, posits that a completely submerged ball experiences significant downward pressure but questions the upward pressure, suggesting it may not remain submerged.
  • Another participant counters that pressure increases with depth, indicating that the pressure at the bottom of the ball is indeed greater than at the top, which would contribute to an upward force.
  • Dasky raises a related scenario involving a box resting on the bottom of a pool, questioning whether it would remain submerged given that the bottom face has no upward pressure from water.
  • A later reply suggests that if the box is arranged such that no water can enter, it could theoretically remain submerged, although this scenario is described as difficult to achieve.

Areas of Agreement / Disagreement

Participants express differing views on the effects of pressure on submerged objects, with no consensus reached on the implications of these pressures for the ball or the box scenario.

Contextual Notes

Participants discuss the assumptions regarding pressure distribution in fluids and the conditions necessary for objects to remain submerged, but these assumptions are not fully resolved or agreed upon.

dasky
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Greetings,
I have a question about the classic Archimede's principle.
A ball inflated with air will not sink into water. My understanding is that it will be pushed from all directions by the surrounding water trying to fill the space occupied by the ball. So there will be a pressure downwards formed by the water column above the ball, and there will be pressure upwards from the water below the ball, and obviously on the sides.
My question is: if a ball is completely submerged there will be a lot of pressure downwards but no or very little pressure upwards, will the ball remain submerged?
Thanks
Dasky
 
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dasky said:
My question is: if a ball is completely submerged there will be a lot of pressure downwards but no or very little pressure upwards,
No, your premise is wrong. The pressure is higher at the bottom of the ball (it is deeper and pressure grows linearly with depth).
 
Then what about a different container, like a box, resting on the bottom of a pool? the face in contact with the surface of the pool will have no water pushing upwards, so will it remain down?
 
dasky said:
Greetings,
I have a question about the classic Archimede's principle.
A ball inflated with air will not sink into water. My understanding is that it will be pushed from all directions by the surrounding water trying to fill the space occupied by the ball. So there will be a pressure downwards formed by the water column above the ball, and there will be pressure upwards from the water below the ball, and obviously on the sides.
My question is: if a ball is completely submerged there will be a lot of pressure downwards but no or very little pressure upwards, will the ball remain submerged?
Thanks
Dasky
The pressure under the ball will be greater because it is deeper.
By the way, I have noticed that if such a ball is pushed down under water and then released, the upward acceleration cannot exceed -g. This is because water has to fall by gravity into the space vacated in order to create the upthrust.
 
dasky said:
Then what about a different container, like a box, resting on the bottom of a pool? the face in contact with the surface of the pool will have no water pushing upwards, so will it remain down?

If you can arrange it such that really no water slips in. This is difficult, but a priori possible.
 

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