Is there really any such thing as an incompressible liquid?

In summary, the conversation discusses the relationship between pressure and depth, using the equation pgh where p represents the density of the liquid and g represents acceleration due to gravity. The conversation also explores the idea of an incompressible liquid and how it relates to the pressure experienced by an object at a certain depth. It is concluded that even with a supposedly incompressible liquid, there must still be some compression present. However, the conversation is more of a philosophical discussion than a homework problem.
  • #1
Abu Rehan
5
0

Homework Statement


Given- Pressure increases with depth.


Homework Equations


We know that pressure under a depth h is given by pgh. Where p=density of liquid, g= acceleration due to gravity.


The Attempt at a Solution


Let us take an example.
There is an ocean of a liquid which is 100% incompressible. At a depth h there is a lobster experiencing a pressure of pgh. Suppose we go deep inside the ocean and seal the lobster and the liquid in a box. Clearly, the lobster is still experiencing the same amount of pressure. We bring the sealed box above with us. We take another box, pour some water in that, put a lobster in that and seal the box.
Now observe the two boxes. If the liquid is incompressible then the two boxes are identical(apart from the compression in lobster's body). But we earlier saw that the first lobster is experiencing much more pressure than the second one. So we arrive at a contradiction. Therefore there must be something different in case of the first box i.e., it must have a little compressed liquid. The decrease in volume may be very very little but compression must be there. What is relevant is the pressure. Some liquid may apply huge amount of force by getting compressed very little while others may apply that amount of force by getting compressed a lot.
Therefore however incompressible a liquid may be, it cannot be 100% incompressible.
 
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  • #2
This doesn't appear to be a homework problem, it's more of a philosophy of science issue like light flexible strings and massless pulleys. Possibly it would be better served up in one of the general physics forums for discussion.

Also, you forgot about the compressibility/flexibility of the box material :smile:
 

FAQ: Is there really any such thing as an incompressible liquid?

1. What is an incompressible liquid?

An incompressible liquid is a substance that cannot be compressed or reduced in volume, even under high pressure. This means that its density remains constant regardless of the external forces acting upon it.

2. How do scientists determine if a liquid is incompressible?

Scientists determine if a liquid is incompressible by measuring its bulk modulus, which is a measure of its resistance to compression. A high bulk modulus indicates high incompressibility, while a low bulk modulus indicates compressibility.

3. Are there any real-life examples of incompressible liquids?

Yes, there are many real-life examples of incompressible liquids. Water is a commonly known incompressible liquid, as well as other fluids such as oil, glycerin, and mercury. These liquids are used in many applications, including hydraulic systems, car brakes, and shock absorbers.

4. Can a liquid be completely incompressible?

No, it is not possible for a liquid to be completely incompressible. All liquids have some degree of compressibility, but some have a much higher level of incompressibility compared to others. In most cases, the compressibility of liquids is negligible and can be considered as incompressible for practical purposes.

5. What are the consequences of compressing an incompressible liquid?

Trying to compress an incompressible liquid would require an enormous amount of force, which would likely result in extreme temperatures and potentially cause the liquid to change state. Additionally, the container holding the liquid may also deform or break under the pressure. Therefore, it is not practical or feasible to compress an incompressible liquid.

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