# 6 min solution Hydraulics problem 9



## PEin2010 (Oct 3, 2010)

Reference: Breadth problems 6 minute solutions Water Resources / Hydraulics

Can anyone tell me where the equation for the Force at the top of the hinge comes from? Please see attached.


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## IlPadrino (Oct 4, 2010)

PEin2010 said:


> Reference: Breadth problems 6 minute solutions Water Resources / Hydraulics
> Can anyone tell me where the equation for the Force at the top of the hinge comes from? Please see attached.


Can you post the entire problem?


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## civilized_naah (Oct 4, 2010)

PEin2010 said:


> Reference: Breadth problems 6 minute solutions Water Resources / Hydraulics
> Can anyone tell me where the equation for the Force at the top of the hinge comes from? Please see attached.


It's just a statement of moment equilibrium (taking moments about the top of the gate, where the hinge is):

Resultant fluid force F x distance from top of gate to center of pressure = Closing force at bottom of gate x diameter

Just a situation specific application of sum moments = 0


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