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mass density (metric) |
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weight density |
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specific gravity - ratio of the density of the
substance to the density of water |
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adhesion - attraction between unlike molecules |
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cohesion - attraction between like molecules |
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surface tension - due to cohesive forces in
fluid when the shape is changed |
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capillary action - due to adhesive forces and
the surface tension |
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Viscosity - the internal resistance of a fluid |
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force per unit of area |
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may be due to the weight (density) of a fluid
and the depth. |
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Buoyancy - apparent weight difference of an
object submerged in a liquid due to the pressure difference from top to
bottom |
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Archimedes’ principle - an object in a fluid is
buoyed up with a force equal to the weight of the volume of fluid displaced |
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Pascal’s principle - pressure applied to an
enclosed fluid is transmitted undiminished to every portion of the fluid
and to the walls of the container |
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Fluid Flow |
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Assumptions: |
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streamline |
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incompressible |
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nonviscous |
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Flow rate (R) |
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Constant flow rate – the flow rate in (1) must
equal the flow rate out (2) |
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Bernoulli’s Equation |
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P = absolute pressure |
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r = mass density |
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g = acceleration of gravity |
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h = height (depth) |
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v = velocity |
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Applications of Bernoulli’s Equation |
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Fluids at rest |
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Flow from a small hole in a large tank |
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Venturi meter |
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Lift (force) on an airplane wing |
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The air speed past the upper surface of a wing
is 352 km/h (98 m/s) and past the lower surface is 320 km/h (89 m/s). The
density of air is 1.21 kg/m3. Determine the lift on a wing with
area of 38 m2. |
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F = ? |
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v1 = 98 m/s v2 = 89 m/s r = 1.21 kg/m3
A=38 m2 |
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DP = 1/2
r Dv2 F = DP A |
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DP = 1/2
(1.21) (982 -892) =
1018 N/m2 |
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F = 1018 (38) = 38700 N (approx. 8700 lbs) |
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Notes