This

**preview**shows page 1. to view the full**4 pages of the document.**•Fluid: liquid or gas

•Fluid statics: study of fluids at rest in equilibrium

12.1 Density

•Density ( )ρ = mass / Volume

•

oUnit: kg / m^3

•Specific Gravity: ratio of material's density to the density of water (1000 kg/m^3)

•

oNo units

•Average density

•

oHuman body (bones vs fat)

oAtmosphere

•Useful for determining battery charge

Example 12.1 The Weight of a Roomful of Air

Q) Find mass and weight of air at 20C in a room w/ 4.0 m x 5.0 m floor and a ceiling 3.0 m high, and

the mass and weight of an equal volume of water.

A) V = (4.0)(5.0)(3.0) = 60 m^3

m(air) = (air)V = (1.20 kg/m^3)(60 m^3) =ρ 72 kg

w(air) = m(air)g = (72g)(9.8 m/s^2) = 700 N = 160 lb

m(water) = (water)V = (1000 kg/m^3)(60 m^3) =ρ 6.0 x 104 kg

w(water) = m(water)g = (6.0 x 10.4 kg)(9.8 m/s^2)

= 5.9 x 10^5 N = 1.3 x 10^5 lb = 66 tons

12.2 Pressure in a Fluid

•Pressure (p) = dF(perp) / dA

•

oIf pressure is the same at all points of a finite plane then

o

p = F(perp) / A

oF(perp) = net normal force on one side of surface

oUnit: 1 pascal (Pa) = 1 N/m^2

o

1 bar = 10^5 Pa

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