Solids and Fluids

States of MatterDeformation of SolidsDensity and Pressure

Familiar States of Matter• Solids – atoms held together by ___________ forces

– Crystalline has _________ structure (a)– Amorphous has __________ structure (b)

• Liquids – forces do not keep atoms/molecules in fixed positions and they can _______ (c)

• Gases – molecules in constant _________ motion, widely separated, and only exert ______ forces on each other

Fig. 9.2, p. 269

Exotic States of Matter• Plasma – like a gas but

electrons are ________ from atoms

• Dark Matter – _______, inferred from motion of stars orbiting centers of galaxies

• Dark Energy – invisible, one explanation for rapid ___________ of universe

Deformation of Solids:Stress and Strain

• Stress is the ______ ___ ____ _____ causing deformation

• Strain is a measure of the _________ of deformation

• For small stresses, stress is __________ to strain

Fig. 9.4, p. 271

1.9strainmodulus elasticstress

Young’s Modulus: Elasticity in Length• Force is __________ to

area A• Force is “tensile” –

produces ________• Tensile ______ is L/L0

• Force per unit area has units of ________ (Pa)

• Y is Young’s modulusFig. 9.3, p. 270

2mN1Pa1 3.90L

LY

A

F

Shear Modulus: Elasticity of Shape

• Force is ________ to area A• Force produces ____ stress• Shear ______ is x/h• S is Shear modulus

3.9h

xS

A

F

Fig. 9.4, p. 271

Bulk Modulus: Volume Elasticity• Force _______ applied to

all sides (perpendicular)• Volume ____ is P=F/A

• Volume _____ is V/V

• B is Bulk modulus• B is always ________• _____________ is B-1

5.9V

VBP

Fig. 9.6, p. 272

Density and Pressure

• Density is mass _______ by volume• Specific gravity is ratio of density to density of

_______• Pressure is ______ per unit area• In a fluid molecules are free to move so it can

not sustain a _____ stress, only _____ stresses

6.9V

M 7.9

A

FP

Pressure Variation with Depth• Fluid at rest in container• All portions in static __________• All points at same depth at same

___________• Consider shaded volume

Fig. 9.11b, p. 279

012 MgAPAP

21 yyAAhVM

10.92112 yygPP

11.90 ghPP

Pascal’s Principle• A change in __________

applied to an enclosed fluid is transmitted ___________ to every point in the fluid and the walls of the container.

Fig. 9.14a, p. 281

21 PP 2211 AFAF

1212 AAFF

Measuring Pressure

• Open tube manometer• Gauge pressure is P − P0

Fig. 9.16, p. 283

ghPPPP BA 0

• Barometer

• Gives atmospheric pressure P0

• 1 atm equivalent to 0.76 m of Hg

Archimedes’ Principle• Buoyant force is equal to the weight of fluid ________

by an object

b12.9fluidfluid gVB

Fig. 9.19, p. 286

• Objects less dense than fluid ____ (a)

• Objects more dense than fluid ____ (b)

Totally Submerged Objects

mamgB F

Examine Newton’s 2nd Law

gVgVgV objobjflobjobjobjfl F

magV objobjfl

objfl VV

Floating Objects

0 mgBF

Examine Newton’s 2nd Law

gVgV objobjflfl

objfl VV

mgB

Fig. 9.20, p. 286

13.9obj

fl

fl

obj

V

V