What Happens to an Object in a Vacuum Filled Jar?

  • Thread starter LeoYard
  • Start date
In summary, when a jar filled partially with water has an object floating in it and is then closed and a vacuum pump is used to pump the air out, the object will either stay in the same position or sink, depending on its density compared to the water. If the object is rigid and less dense than the water, it will sink. If it is elastic or more dense than the water, it will stay in the same position. The amount of water and the size of the container will also play a role in the outcome.
  • #1
LeoYard
16
0
A jar filled partially with water has an object floating in it. The jar is open. Now, if the jar is closed and a vacuum pump is used to pump the air out, what will happen to the floating object? will it rise up more or sink or ...? and why?

What do you think of the following approach :

Normally, It would be impossible to pump all the air out but if you theoretically did, (assuming that the jar doesn't shrink) you would be forcing the water to occupy a large space thus turning it into water vapour. (similarly, if you add pressure to a tank of propane (vapour), it turns into liquid due to pressure.

So if it turns into gas, the object will no longer float.

But thinking more logically, If the object floats in water, that would mean that there is either air trapped in the object or the object is less dense than the water.

If there is air, the vacuum would remove it, thus expanding (more space between the particles) the object at the same rate as the water.

So assuming that the object remains intact (not expanded to the point that the molecules separate), the object will stay in the same position and neither rise or fall.
 
Physics news on Phys.org
  • #2
If you sucked the air out of the jar, then the density of the water would decrease. Thus the object would be more dense than the water. I conjecture that the object would sink. (I'm not saying I'm right; that's why it's a conjecture!)
 
  • #3
Cristo, you assume the object will not change in density (and that its density was very close to that of water, to begin with). If it were a marshmallow..
 
  • #4
cesiumfrog said:
Cristo, you assume the object will not change in density (and that its density was very close to that of water, to begin with). If it were a marshmallow..

That's a very good point! I just went with my gut on that one, which I probably shouldn't do in future! :blushing: However, if the object was pretty much rigid, and was only just floating, then my guess wasn't far off!
 
  • #5
I'm with Cristo on this one. The OP didn't specify that the floating object was elastic. If it isn't, and there's no reason to think that it is, then it will retain its original density which will be greater than that of the expanded liquid.
 
  • #6
I reckon the typical object will continue floating, since water isn't very compressible. (Of course, the water level will rise slightly, and I'd naively expect the object to also rise slightly, just less than the water level.)
 
Last edited:
  • #7
I didn't think of this earlier, but I now believe that it would depend upon how much water there is and how large the container is. The first time around, I was thinking that all of the liquid would expand to fill the available volume. Now I'm inclined to believe that there'll be liquid on the bottom with vapour above. If that's the case, then the object will float on the liquid surface.
 

Related to What Happens to an Object in a Vacuum Filled Jar?

1. What is a vacuum filled jar?

A vacuum filled jar is a container that has had all air and other gases removed from it, creating a vacuum or a space with no air or gas. The jar is usually made of glass or a similarly sturdy material that can withstand the pressure of the vacuum.

2. What happens to an object in a vacuum filled jar?

In a vacuum filled jar, the object will experience no air resistance or friction. This means that it will continue to move at a constant velocity in a straight line, unless acted upon by an external force. The lack of air also means that there will be no sound or heat transfer between the object and the jar.

3. How does the object behave in a vacuum filled jar compared to in the air?

In a vacuum filled jar, the object will behave differently than in the air. This is because the lack of air resistance and friction will affect its movement and interactions. For example, a feather will fall at the same rate as a heavier object in a vacuum filled jar, while in the air, the feather would experience more air resistance and fall slower.

4. What are the practical applications of a vacuum filled jar?

A vacuum filled jar has a variety of practical applications in science and technology. It is commonly used in experiments and research to study the behavior of objects in a vacuum, as well as in industries such as food packaging, where creating a vacuum can help preserve food for longer periods of time.

5. Can living organisms survive in a vacuum filled jar?

No, living organisms cannot survive in a vacuum filled jar. This is because they require oxygen and other gases present in the air to breathe and survive. In a vacuum, these gases are absent, making it impossible for living organisms to survive.

Similar threads

Replies
5
Views
666
  • Classical Physics
Replies
29
Views
2K
  • Other Physics Topics
Replies
6
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
1K
  • Mechanical Engineering
Replies
11
Views
2K
Replies
2
Views
1K
Replies
8
Views
1K
Replies
4
Views
758
Replies
17
Views
2K
Replies
3
Views
2K
Back
Top