Fluid Mechanics- Pressure on a gate

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SUMMARY

The discussion focuses on calculating the pressure on a gate in fluid mechanics, specifically using the equations Fw=γAH and Ycp=bh³/(12)(h/2)b + (h/2). The user calculated the force (Fw) to be 1,177,200 N and the centroid's vertical position (Ycp) as 3.33 m. However, there is a discrepancy with the expected pressure (P), which the user calculated as 393 kN, while the textbook states it should be 523 kN. The confusion arises from the lack of clarity regarding the angle P makes with the horizontal or vertical.

PREREQUISITES
  • Understanding of fluid mechanics principles, specifically hydrostatic pressure.
  • Familiarity with the equations of moments and centroid calculations.
  • Knowledge of trigonometric functions and their application in physics.
  • Experience with calculating forces acting on submerged surfaces.
NEXT STEPS
  • Review hydrostatic pressure calculations in fluid mechanics.
  • Study the method for determining the centroid of irregular shapes.
  • Learn about the application of moments in static equilibrium problems.
  • Examine case studies involving pressure on gates and submerged surfaces.
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Students studying fluid mechanics, engineers working on hydraulic systems, and anyone involved in the design and analysis of gates in fluid environments.

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Homework Statement



http://imgur.com/vXkg0


Homework Equations



Fw=γAH

Ycp=bh3/(12)(h/2)b + (h/2)

The Attempt at a Solution



I found the angle of the gate from the horizontal to be 53.1 degrees. Using this, I found y to be 2.5m and H (vertical distance to centroid) to be 6 m (2.5sin(53.1)+4).

I then found Fw=9810*6*(4*5)=1177200N, and Ycp=(4*53)/(12*20*2.5) +2.5=3.33m.

By taking the moment at the ground, I found Fw*(5-3.33)-5P=0, so P= 393kN. My book says the answer should be 523 kN. Help please.
 
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The picture does not show the angle P makes with the horizontal or vertical, so the question looks unanswerable to me. P could be an angle perpendicular to the 5m line or at some angle away from perpendicularity.
 
I believe that P is supposed to be perpendicular surface (opposing Fw)
 

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