Keep working on the liquid pressure problem

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Homework Help Overview

The discussion revolves around a problem related to liquid pressure and forces acting on a piston. Participants are analyzing the relationship between gravitational force and pressure in a fluid system.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants are examining different expressions for the force on a piston, questioning which formula accurately represents the situation. There is a focus on understanding the implications of pressure and area relationships in the context of fluid mechanics.

Discussion Status

Some participants express uncertainty regarding the correct expression for the force on the piston and seek clarification. Others provide insights into the pressure distribution and force calculations, indicating a productive exchange of ideas without reaching a definitive conclusion.

Contextual Notes

There is mention of assumptions regarding friction and the areas of the pistons, which may influence the calculations being discussed. Participants are also reflecting on their understanding of the problem, suggesting varying levels of familiarity with the concepts involved.

vxiaoyu18
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Homework Statement
Deep understanding of liquid pressure formula.
Relevant Equations
F=ρgSH
20200101011314-.jpg

Without calculating the friction, if the force of gravity on the piston, the initial force F on the piston S is what?
1. F=-ρgSH;
2. F=-(1/2)ρgSH;
3. F=0;
4. Other.
I'm not sure which is the correct result, can someone help me analyze it again?
 
Last edited:
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The force on the left side of the blue piston is ##-\rho g H S_1##. This must also be the force on the right side of the blue piston. So, the pressure inside the compartment must be ##-\rho g H/2## (since the area on the right side of the blue piston is twice the area on the left side of the blue piston). Since S = S1, that means that the force on the left and right sides of the red piston must be ##-\rho gH S/2##.
 
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Thank you for your patience. I finally understand. The calculation process of this method is very clear. Is F=-(1/2)ρgSH.
 
vxiaoyu18 said:
Thank you for your patience. I finally understand. The calculation process of this method is very clear. Is F=-(1/2)ρgSH.
That's what I said.
 
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Likes   Reactions: berkeman

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