Fluids and pressure

  • Thread starter etothey
  • Start date
  • #1
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Homework Statement


Pressure_2.jpg: http://www.imageupload.org/thumb/thumb_8609.jpg
A vertical dam wall has a width w. Water is filled to a height H behind the dam. Calculate the resultant force on the dam wall.



Homework Equations


P=F/A
P= Pa + p*g*h





The Attempt at a Solution


Using picture to solve the question
P=F/A
A=H*W
Thus P=Pa g*h*p where p is density and P is pressure.
Thus F=P*A=H*W*(Pa + gHp) where g is gravity.

Is this correct?
 

Answers and Replies

  • #2
124
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Your solution, as I've understood it, would work if the pressure were uniform, that is, constant. However, it changes as you go down, so you would need to perform an integration to determine the net force.
 
  • #3
22
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Your solution, as I've understood it, would work if the pressure were uniform, that is, constant. However, it changes as you go down, so you would need to perform an integration to determine the net force.

Aha, I see. This is first fluid question I had involving integration.
Thus, I integrated [tex]\int[/tex]Po + pgh dh from 0 to H.
Getting P=PaH + pgH^2/2.
Thus
PA = HW(PaH + pgH^2/2).
Better now?
 
  • #4
22
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anyone?
 

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