# When is Pascal's Principle applicable?

## Homework Statement

Which of the following statements about Pascal’s principle is true?
A. It is valid only for incompressible fluids
B. It explains why light objects float
C. It explains why the pressure is greater at the bottom of a lake than at the surface
D. It is valid only for objects that are less dense than water
E. None of the above are true

## The Attempt at a Solution

The answer is suppose to be E. I thought it was A. I thought Pascal's principle was only applicable to incompressible fluids.

So if A isn't true, then is Pascal's principle true for gases? What are the limits of pascal's principle?

Thanks

Mentor
What is your most precise statement of Pascal’s principle?

Homework Helper
Gold Member
I can understand how it is easy to think A is the answer. One practical application of Pascal's Principal is the hydraulic lift, which works best when the fluid is incompressible. But looking at the principal - http://hyperphysics.phy-astr.gsu.edu/hbase/pasc.html you can see that the pressure "transfer" has nothing to do with compressible

@Chestermiller here is my most precise definition:
A change in the pressure applied to an enclosed incompressible fluid is transmitted undiminished to every portion of the fluid and to the walls of its container.
(note that this was copied from the book and I know it includes incompressible in it. )

Mentor
@Chestermiller here is my most precise definition:
A change in the pressure applied to an enclosed incompressible fluid is transmitted undiminished to every portion of the fluid and to the walls of its container.
(note that this was copied from the book and I know it includes incompressible in it. )
This is not my understanding of Pascal's principle. For what it's worth, my understanding is that, at a given location in a fluid, the pressure acts equally in all directions (i.e., is isotropic).