What will happen when a body is equally dense as the liquid?

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Discussion Overview

The discussion revolves around the behavior of objects with equal density to a liquid, specifically in the context of flotation principles. Participants explore theoretical and practical implications of buoyancy, displacement, and the conditions under which objects may float or sink.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that if an object has the same density as the liquid, it will float, but seeks clarification on the underlying reasons.
  • Another participant introduces the concept of "displacement" and relates it to ships.
  • It is suggested that surface tension may play a role in the floating behavior of objects with equal density to water.
  • Some participants argue that an object of equal density will not move up or down but will remain at rest unless acted upon by external forces, such as water currents.
  • There is a claim that if the object is exactly the same density as the liquid, it will sink to a point where no part is above the surface, potentially leading to confusion about the definition of "floating."
  • Multiple participants discuss the challenges of achieving neutral buoyancy, noting that any slight deviation in density can lead to sinking or floating.
  • One participant raises questions about the effects of water pressure and gravity on objects at varying depths, suggesting that these factors contribute to the complexity of the situation.
  • Another participant mentions that changes in temperature and compressibility of the object can affect its density and buoyancy behavior.

Areas of Agreement / Disagreement

Participants express differing views on whether an object with equal density will float or sink, with some asserting it will remain submerged while others suggest it may float just below the surface. The discussion remains unresolved, with multiple competing interpretations of the behavior of such objects.

Contextual Notes

Participants highlight limitations in achieving exact neutral buoyancy, including the effects of external forces, temperature changes, and the compressibility of materials, which may influence the object's behavior in the liquid.

RS_Physics
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I am studying Floatation in school and I have some doubts. I get that if an object is denser than the liquid its placed on, it will sink, and if it is less dense then it floats. But what happens when the density of both (the object and the liquid) are same? Will it float or sink?

My notes say that if it has a lesser density, then it float PARTIALLY &
if it has an equal density to that of the liquid it will FLOAT.

But how and why? I searched the net and found different explanations that confused me even more. Hope you can help.

KUDOS. :D
 
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Read up on "Displacement". For example ships.
 
If the liquid is water, and the body has the same density as water, then it will most likely float because of the surface tension of water caused by hydrogen bonds.
 
If an object is exactly the same density as the liquid, it will not move up or down. It will just stay right where it is (unless it is pushed around by water currents). If you put it on the surface, it will remain on the surface [EDIT: see CWatters post below for clarification]. If you push it under the water, it will stay under the water, without moving up or down.

It's not so easy to achieve neutral buoyancy exactly. Fish and submarines do it by having an internal container that they can pump air and water into or out of in order to change their density.
 
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If an object is exactly the same density as the liquid, it will not move up or down. It will just stay right where it is (unless it is pushed around by water currents). If you put it on the surface, it will remain on the surface.

Perhaps best to clarify that last line.. It will actually sink into the water so that no part of the object is above the surface.
 
There are three cases..

If an object is less dense than water it will sink into the water until the mass of water displaced equals the mass of the object. If pushed further under it will float back up.

If the object is of equal density it will sink into the water so that no part of the object is above the surface. It may or may not "float" just but entirely below the surface. As eigenperson said, if pushed down it might stay at the new depth but that's tricky.

If the object is of greater density it will sink.
 
CWatters said:
There are three cases..

If an object is less dense than water it will sink into the water until the mass of water displaced equals the mass of the object. If pushed further under it will float back up.

If the object is of equal density it will sink into the water so that no part of the object is above the surface. It may or may not "float" just but entirely below the surface. As eigenperson said, if pushed down it might stay at the new depth but that's tricky.

If the object is of greater density it will sink.

Why is it tricky? If pushed down it will stay at the new depth unless acted on by another force. The force of water pressure would be equal on all sides would it not? Although there is less pressure exerted on it near the surface than there would be at greater depth. But that could be negligible depending on the size of the object. Also at such negligible magnitude of forces doesn't gravity still play a role? On second thought maybe you're right, this could get tricky ;) But tricky is interesting.:approve:
 
What I meant was it's hard to achieve exactly neutral buoyancy in the first place. Any slight error in the density and the object starts to float or sinks. If the object is slightly compressible then changes in water pressure may change it's volume slightly and hence it's density. Even temperature changes may effect it. This effect is exploited here.

http://www.howstuffworks.com/question663.htm

As the temperature changes a bubble will transition through the neutral density point and either float or sink.
 
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