How Do Piston Sizes Affect Height Differences in Hydraulic Systems?

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SUMMARY

The discussion focuses on calculating the height difference between two pistons in a hydraulic system, specifically a 4.7 cm diameter piston weighing 1.7 kg and a 12 cm diameter piston weighing 3.7 kg, using a fluid density of 750 kg/m³. Participants clarify that while the pressure at the same level in the fluid is equal, the differing piston areas result in different forces acting on each piston. The correct approach involves calculating the forces on each piston to determine the height difference, rather than relying solely on pressure equations.

PREREQUISITES
  • Understanding of Pascal's principle in hydraulics
  • Knowledge of fluid density and its role in pressure calculations
  • Familiarity with the equations of pressure, specifically P = F/A
  • Basic principles of force and area in mechanical systems
NEXT STEPS
  • Study the application of Pascal's principle in hydraulic systems
  • Learn how to calculate force and pressure using the formula P = F/A
  • Explore the relationship between piston area and height difference in hydraulic systems
  • Investigate real-world applications of hydraulic systems in engineering
USEFUL FOR

Mechanical engineers, physics students, and anyone involved in hydraulic system design or analysis will benefit from this discussion.

map7s
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In a hydraulic system the piston on the left has a diameter of 4.7 cm and a mass of 1.7 kg. The piston on the right has a diameter of 12 cm and a mass of 3.7 kg. If the density of the fluid is 750 kg/m3, what is the height difference h between the two pistons?

I'm not even sure what equation I could use to get started on this problem. I was looking at the equation P2=P1+pgh but the pressure would be the same at both points.
 
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map7s said:
In a hydraulic system the piston on the left has a diameter of 4.7 cm and a mass of 1.7 kg. The piston on the right has a diameter of 12 cm and a mass of 3.7 kg. If the density of the fluid is 750 kg/m3, what is the height difference h between the two pistons?

I'm not even sure what equation I could use to get started on this problem. I was looking at the equation P2=P1+pgh but the pressure would be the same at both points.
The equation you wrote for the pressures is based on the fact that at a common level that is in the liquid on both sides the pressure is equal. P1 and P2 are the pressures at the tops of the liquid, which are at different levels.
 
right, that was one of the reasons as to why i was confused...I also looked at another equation, but it was in regards to a similar problem where the one side that was lower was due to a different density of liquid added and then they used the equation p(water)h1=p(liquid)h2...I was trying to find out some way to tweak that equation so that I would be able to use it for this problem, but it's not really working...
 
map7s said:
right, that was one of the reasons as to why i was confused...I also looked at another equation, but it was in regards to a similar problem where the one side that was lower was due to a different density of liquid added and then they used the equation p(water)h1=p(liquid)h2...I was trying to find out some way to tweak that equation so that I would be able to use it for this problem, but it's not really working...
You only have one liquid, which is easier to deal with. You have different piston areas, so even if the two sides were at the same level (same pressure) you would have different forces on the pistons. You need to find the forces acting on the pistons to find the pressure on each side.
 

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