TBR Physics, Chapter 7 (Fluids and Solids), Passage 4, Question 26

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MDminded

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Q. There is a diagram that shows three tanks which contain objects of the same size and density, at the same depth in a tank (text). The tanks all vary in shape and volume of water (my observation). Which object experiences the greatest pressure?

A. All three objects experience the same pressure.


TBR says "Although the three tanks have different shapes, the height of the fluid in all three cases is the same. Pressure at a depth "h" below the surface of the fluid is rho*g*h. Since the objects are all at the same depth "h", they all experience the same pressure."

I got this question wrong. My thought process behind it was that if the area of each tank was different, the tank with the least area would have the greatest amount of pressure. Why is my thinking incorrect? Why do I look at the depth instead?

Thanks for your help!

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Q. There is a diagram that shows three tanks which contain objects of the same size and density, at the same depth in a tank (text). The tanks all vary in shape and volume of water (my observation). Which object experiences the greatest pressure?

A. All three objects experience the same pressure.


TBR says "Although the three tanks have different shapes, the height of the fluid in all three cases is the same. Pressure at a depth "h" below the surface of the fluid is rho*g*h. Since the objects are all at the same depth "h", they all experience the same pressure."

I got this question wrong. My thought process behind it was that if the area of each tank was different, the tank with the least area would have the greatest amount of pressure. Why is my thinking incorrect? Why do I look at the depth instead?

Thanks for your help!

Why would you look at area?
Whats the difference in pressure for an object at the same depth in the ocean or in a pool? By your logic the pool would have a larger pressure and the ocean having a huge area would have very little pressure.
 
Why would you look at area?
Whats the difference in pressure for an object at the same depth in the ocean or in a pool? By your logic the pool would have a larger pressure and the ocean having a huge area would have very little pressure.

I considered area since pressure is defined as force over an area. I reverted to the definition.

I understand your intuition/reasoning with regards to the pool/ocean...but why do I not consider area and instead consider depth. Is it because it's an enclosed liquid?
 
Q. There is a diagram that shows three tanks which contain objects of the same size and density, at the same depth in a tank (text). The tanks all vary in shape and volume of water (my observation). Which object experiences the greatest pressure?

A. All three objects experience the same pressure.


TBR says "Although the three tanks have different shapes, the height of the fluid in all three cases is the same. Pressure at a depth "h" below the surface of the fluid is rho*g*h. Since the objects are all at the same depth "h", they all experience the same pressure."

I got this question wrong. My thought process behind it was that if the area of each tank was different, the tank with the least area would have the greatest amount of pressure. Why is my thinking incorrect? Why do I look at the depth instead?

Thanks for your help!


No matter what the area of the container is, if all three objects are at the same height they experience the same amount of pressure because the fluid in which they are immersed is the same.

Your thinking is incorrect because you forgot to consider the forces acting on the object in all directions. If all of the objects are at the same height, the force pushing up/down/left/right on one object is the same as the force pushing up/down/left/right on another object.

Make sense?
 
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No matter what the area of the container is, if all three objects are at the same height they experience the same amount of pressure because the fluid in which they are immersed is the same.

Your thinking is incorrect because you forgot to consider the forces acting on the object in all directions. If all of the objects are at the same height, the force pushing up/down/left/right on one object is the same as the force pushing up/down/left/right on another object.

Make sense?

Yes. Thank you both!
 
No matter what the area of the container is, if all three objects are at the same height they experience the same amount of pressure because the fluid in which they are immersed is the same.

Your thinking is incorrect because you forgot to consider the forces acting on the object in all directions. If all of the objects are at the same height, the force pushing up/down/left/right on one object is the same as the force pushing up/down/left/right on another object.

Make sense?

Then when does area matter?
 
Then when does area matter?

I think you may be confusing two concepts.

For this question about the pressure experienced by the objects, you only want to consider buoyant forces. (The reference frame will be in along the y axis)

Area is considered if you are trying to guage the amount of pressure experienced at a certain point inside a pipe filled with a fluid. The amount of pressure changes when the cross sectional area of the pipe changes. (The reference frame will be along the x axis).
 
I think you may be confusing two concepts.

For this question about the pressure experienced by the objects, you only want to consider buoyant forces. (The reference frame will be in along the y axis)

Area is considered if you are trying to guage the amount of pressure experienced at a certain point inside a pipe filled with a fluid. The amount of pressure changes when the cross sectional area of the pipe changes. (The reference frame will be along the x axis).

Got it. Thanks.
 
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