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# P = F/A

Pressure. P = F/A. At any point in a fluid (liquid or gas), pressure is exerted equally in all directions. The force exerted by a fluid (liquid or gas) at rest acts perpendicular to the surfaces the fluid contacts. .

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## P = F/A

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1. Pressure P = F/A At any point in a fluid (liquid or gas), pressure is exerted equally in all directions

2. The force exerted by a fluid (liquid or gas) at rest acts perpendicular to the surfaces the fluid contacts. The force exerted by a fluid (liquid or gas) at rest acts perpendicular to the surfaces the fluid contacts. (Otherwise the fluid would !) move

3. If a fluid is incompressible, ρ is constant. The pressure at any depth due to the weight of the liquid above it may be determined by…

4. Fg = mg = ρV m = ρV = Ah V = Ah So… P = F/A = mg/A= ρVg/A = ρAhg/A= ρgh h = height (or pressure head)

5. P = ρgh This pressure is a gaugepressure, which accounts only for the fluid’s weight (and does not account for atmospheric pressure). Pgauge = Pabsolute – Patm

6. Absolutepressure includes the fluid’s weight and also accounts for atmospheric pressure. Pabsolute = Pgauge + Patm = ρgh + Patm

7. Pressures at equal depths within a uniform liquid are the same. P P P P P P

8. If ρ changes are slight… DP = ρgDh

9. Pascal’s Principle – A pressure applied to a confined fluid increases the pressure throughout by the same amount. What’s easier to catch than heffalumps, but harder to hold onto?

10. Hydraulics work because Pascal’s Principle is applied to an incompressible fluid.

11. Pin = Pout Fin = Fout Ain = Aout Aout= Fout = IMA Ain=Fin P

12. Pin = Pout Fin = Fout Ain = Aout Aout= Fout = IMA Ain=Fin P

13. Pin = Pout Fin = Fout Ain = Aout Aout= Fout = IMA Ain=Fin P out P P in

14. IMA (Ideal Mechanical Advantage) is the number of times the device would increase the input force in the absence of friction.

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