9 Solids

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9 Solids Fluids

• elasticity of solids
• pressure and pascals principle
• buoyancy and archimedes principle
• Homework
• 1, 3, 5, 37, 39, 56, 69, 70.

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Solid Deformation

• stress force/area pressure
• strain fractional change in length
• Solid Moduli stress/strain stiffness

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Solid Deformation

• Length Change
• stress F/A, strain DL/Lo,
• Youngs Modulus, Y stress/strain.
• Volume Change
• stress F/A p, strain -DV/Vo,
• Bulk Modulus, B -Dp/(DV/Vo)

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Pressure, p

• p force/area
• Unit pascal, Pa
• 1 Pa 1N/m2.
• Example 100N applied to 0.25m2. Pressure
  100/0.25 400N/m2.

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Density

• r mass/volume
• SI Unit kg/m3
• common unit g/cm3
• 1,000 kg/m3 1 g/cm3

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Gauge Pressure is Differential Pressure
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Depth and Fluid Pressure

• P Po rgd
• P is the pressure at depth d.
• Po is the pressure at the fluid surface
• r is the fluid density
• Example increase in pressure at a depth of 1m in
  water (1,000)(9.8)(1.0) Pa

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Barometer
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Pascals Principle
Example A2/A1 100 F2/F1 100
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Buoyancy and Archimedes Principle
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L0.5m cube of steel in water

• Vo L3 (0.5m)3 0.125 m3
• FB (fl.density)(Vo)(g)
• (1,000kg/m3 )(0.125 m3 )(9.8N/kg)
• 1225N
• Compare FB to W of object
• W mg (ob.density)(ob.volume)(g)
• (7,800)(0.125)(9.8)
• 9555N
• What is its weight when under water?
• W W FB 8330N

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1kg object is weighed in water

• W 9.2N. What is its density?
• FB W W 9.8N 9.2N 0.6N
• FB (fl.den.)(ob.vol.)(g) 0.6N
• FB (1000)(ob.vol.)(g) 0.6N
• (ob.vol.) 6.12x10-5cubic meter
• (ob.den.) mass/vol. 1kg/(6.12x10-5)
• 16,333 kg/m3. 16.333 g/cm3.
• This is not pure gold.

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Example Object mass 0.150kg density 2g/cm3 is
weighed in water.
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Example calculate speed water exits the hole in
terms of the given parameters.
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