Fluid mechanics help, where am i going wrong?

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SUMMARY

The discussion centers on calculating the force exerted by fluid pressure on a wall in a fluid mechanics problem. The user is attempting to find the force \( F_h \) using the equation \( P_{base} = \rho \cdot h \cdot g \) with a density of 1800 kg/m³ and gravitational acceleration of 9.81 m/s². A key insight provided is to assume a depth of 1 meter when one dimension is omitted, allowing for the calculation of the resultant force \( F_h \) as pressure multiplied by effective height. The user is also guided on how to determine the tipping point and maximum friction force by summing torques about a specified point.

PREREQUISITES
  • Understanding of fluid mechanics principles, specifically hydrostatic pressure.
  • Familiarity with the equations of fluid statics, including \( P = \rho \cdot g \cdot h \).
  • Knowledge of calculating moments and torques in mechanical systems.
  • Ability to interpret and manipulate units, particularly converting pressure to force (N).
NEXT STEPS
  • Learn how to apply hydrostatic pressure equations in various fluid scenarios.
  • Study the concept of effective height in fluid mechanics problems.
  • Explore the calculation of moments and equilibrium in static systems.
  • Investigate the principles of retaining walls and their design considerations.
USEFUL FOR

Students and professionals in engineering, particularly those focusing on fluid mechanics, structural analysis, and civil engineering applications related to retaining walls and fluid pressure calculations.

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Homework Statement


[PLAIN]http://img30.imageshack.us/img30/6918/screenshot20110828at111.png

Homework Equations


P_base= rho * h * g = 1800 kg/m^3 * h * 9.81 m/s^2 = 17658 * h kg/(m^2 s^2)
F_h= .5 * h * P_base = 10594.8 * h^2 kg/(m^2 s^2)

The Attempt at a Solution


I am trying to find the force F_h by calculating the pressure at the bottom of the load and creating a resultant. The issue i believe i am having is that there is no depth given so I'm not sure how to calculate the force on a wall since i only have 1 of the walls dimension. Unless I'm reading the problem incorrectly and the width and depth are both .25m? When i do the math the F_h works out to be kg/s^2 instead of Newtons.

Once i figure out the F_h i would then just need to take the moment about A to find the tipping point and the max F_friction to find the highest sliding point, correct? If anyone could guide me as to what I'm doing wrong that would be helpful.
 
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I believe you're on the right track.

When a dimension is omitted in a problem you can be pretty sure it's not needed. Just assume a 1m depth. Then compute the resultant for F_H to get the slip point and sum torques (moments) about A as you say.

Isn't it funny how they say "retaining wall" instead of just "dam"?

PS - force is now pressure * effective height * 1m, you realize.
 

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