How will opening a vacuum box in a vertical water column affect the water level?

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Discussion Overview

The discussion revolves around the effects of opening a vacuum box attached to a vertical water column on the water level. Participants explore the implications of the vacuum's presence and the resulting interactions with the surrounding water, considering both theoretical and practical aspects of the scenario.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes a setup where a vacuum box is attached to a vertical water column and poses a question about the outcome when the box is opened.
  • Another participant requests clarification on the thought process behind the initial question and raises considerations about the density of the box material and the implications of reducing pressure in the column.
  • A participant suggests that when the vacuum box is ruptured, the external air pressure would push water into the box, supporting the idea that the water level would lower (option B).
  • Another participant concurs with the view that the height of the water column is influenced by external air pressure, which would cause water to rise into the box upon rupture.
  • A later reply asserts that the vacuum box would draw in a volume of water equivalent to its internal volume, negating the creation of an air gap at the top of the column.

Areas of Agreement / Disagreement

Participants generally agree that the outcome involves the water level being affected by external air pressure, with multiple viewpoints on the specific mechanics of how the water interacts with the vacuum box upon its opening. The discussion remains somewhat unresolved regarding the exact dynamics involved.

Contextual Notes

Participants mention various assumptions, such as the density of the box material and the conditions under which the scenario is considered (e.g., atmospheric pressure). There are also questions about the volume relationships between the box and the water column that remain unaddressed.

Who May Find This Useful

This discussion may be of interest to those studying fluid dynamics, pressure systems, or anyone curious about the behavior of liquids in response to changes in pressure and vacuum conditions.

alibaba2
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hi to all,
this one may sound silly but i just can't seem to understand how it will work out.
this is the setup - in a vertical water column (state of vacuum) a hollow box is attached to the base. all air from the box has been sucked out and the box contains a vacuum(fig A).

if the lid of the box is opened when inside the column, which of the following will take place?
- the vacuum in the box will automatically be taken by the surrounding water, in this way lowering the level of the water in the basin (fig B)

or

-the vacuum will release an ""empty space"" that will go to the top of the column and lead to the water level being raised (fig C)

10x
 

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Please show us how you have been thinking about it so we can figure out what is behind you getting stuck.

Note: in B and C, the box, itself, is made out of material less dense than water yet can hold it's shape with a vacuum inside?

You can see what happens in a lesser situation, where you have a gas at the top of the column ... how does the column balance? What happens if you reduce the pressure of the gas?

For the picture in B: what happens if the volume of the box is bigger than the volume of water in the dish?
For the picture in C: what happens next?
 
Judging from the experiment shown in the illustration, I'll assume it would take place at normal atmospheric pressures. Say, on Earth, in your conventional classroom?

When the box containing the vacuum is ruptured, the pressure gravity exerts on the air surrounding the setup would continue pushing the water inward, filling in the empty space, as shown in figure-B of your illustration.
 
It is B. The height of the water column is determined by he external air pressure, which will push the liquid in the dish up into the box.
 
so B is the correct option. the vacuum box, once ruptured would simply suck inside it a quantity of the water equivalent to its internal volume. no ""air gap"" will be created at the top of the column.

thank for all the replies. i have understood the physics behind this setup.
 

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