Pascals principle and hydraulic lift

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Discussion Overview

The discussion revolves around Pascal's principle and its application to hydraulic lifts. Participants explore the mechanics of fluid pressure distribution, the relationship between force and area in hydraulic systems, and the implications of Newton's laws in these contexts. The conversation includes conceptual challenges and attempts to build intuition around the principles involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about how a hydraulic lift can exert a larger force than applied, questioning the role of Pascal's principle compared to a rigid rod system.
  • Another participant suggests that equilibrium requires considering forces on all parts of the system, not just the central fluid.
  • Several participants discuss the relationship between force, area, and distance traveled by pistons, referencing conservation of energy and work done.
  • There is a mention of Newton's third law and its application to local interactions within the fluid and between the pistons.
  • One participant seeks a more intuitive explanation of the lever principle as it applies to hydraulic systems.
  • Another participant introduces the concept of virtual work in equilibrium situations, prompting questions about its applicability in Newtonian mechanics.
  • There is a request for a force-based explanation of how the pressure from one piston translates to a larger force on another piston without invoking energy conservation.

Areas of Agreement / Disagreement

Participants generally agree on the basic principles of Pascal's principle and the mechanics of hydraulic lifts, but there are multiple competing views on the interpretation of forces, energy conservation, and the applicability of advanced mechanics concepts like virtual work. The discussion remains unresolved on some points, particularly regarding the clarity of these principles in different contexts.

Contextual Notes

Some participants express uncertainty about the implications of their assumptions, particularly regarding the application of Newton's laws in equilibrium situations and the interpretation of virtual work. There are also limitations in the clarity of how energy conservation applies in specific scenarios discussed.

  • #31
aaaa202 said:
I really liked this part. Does something similar happen when the pistons are not in line but like in the picture in post #21?

Yes. If you want to calculate it in full glory, you can carry out a surface integral of pressure times inward normal to the surface. This gives the net force on the fluid. I in integrating you leave out the pistons then this total force must equal the forces on the pistons.
 

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