Vacuum

A vacuum exists in outer space.

It is the absence of all matter.

Vacuums are relative

Even in outer space some matter exists

But the amount is so small that a person would die if exposed to vacuum without a space suite

States of Matter

Solid

Liquid

Gas

Plasma

Solid

Solid A rigid body, retains its shape unless distorted by a strong force.. Examples: rock, wood, plastic, iron

Liquid

Flow readily,

conform to the shape of their container.

Have a well defined boundary (surface).

More dense than gases.

Examples water, beverages, blood, oil,…

Gas

Flow readily,

conform to the shape and size of their container,

do not have a well defined surface,

can be compressed or expanded readily.

Examples: air, carbon dioxide, helium, steam.

Inside Liguid vs Gas

Plasma

An ionized gas, often referred to as the fourth state of matter.

It consists of positive ions and electrons

interacts strongly with magnetic fields

conducts electricity.

Commonly exists only at higher temperatures or in strong electromagnetic fields

Examples: Sun, candle flame, gases in operating fluorescent, neon, and vapor lights.

Structure or Particles of Matter

Greeks described smallest particles of matter as atoms.

Now we know there are even smaller particles.

Atoms are composed of

Electrons, protons and neutrons.

Protons and neutrons are in the center or nucleus of the atom

Electrons orbit around the nucleus

Neutrons, Protons, Electrons

Neutron Electrically neutral particle residing in the nucleus of an atom.

Proton Positively charged particle residing in the nucleus of an atom.

Electron Negatively charged particle, usually found orbiting the nucleus of an atom.

Elements

One of over 115 different fundamental substances

The simplest and purest forms of matter.

All have the same type of Atom, specifically the same number of protons in the nucleus.

Scientists are still discovering new elements so the number is always increasing.

Examples of Elements

Gold, Silver, Oxygen, Silicon, Nitrogen,….

Nitrogen is the most abundant element. It makes up about 80% of our air.

Silicon is also very abundant, since it occurs in sand, a compound of Silicon and Oxygen.

Molecule/Compound

Two or more atoms combine to form a molecule. If the atoms are different types
it is a compound.

A Compound is something composed of identical molecules of more than one type of atom or element. 2 or more elements combine chemically.

E.G. SiO₂ Is a compound composed of molecules with Silicon and Oxygen atoms.

Mixture

No chemical reaction, thus not a compound

Parts do not combine uniformly, they just intermix.

Parts can be recovered individually.

Example, Instant Cocoa: chocolate, sugar, and milk powder.

Solutions

A homogeneous mixture of two or more substances, which may be solids, liquids, gases, or a combination of these

The parts break down into individual molecules, and intersperse, but do not combine.

E.G. salt in water-salt water

Suspensions

A suspension has tiny particles, but many molecules in one particle.

Not a chemical reaction, thus not a compound

Their particles are larger than molecules thus not a solution.

Suspensions Examples

Mayonaise, Gelatin, Butter, Ice Cream Orange Juice

see http://encyclopedia.thefreedictionary.com/Suspension+(chemistry)

Pressure (p)

The force per unit area for a force acting perpendicular to a surface. The force acting on a surface divided by its area.

P = Force/Area = F/A

Force on the floor= Weight = 100 lbs

Area of shoes surface 30 sq.in.

Pressure on the floor =100/30= 3.33psi

Pressure from spike heels

Heel area = .2x.2in=.04sq.in

Sole area =2 x 4 in = 8 sq.in.

Weight=100 lbs.

On Heel P=100/.04 =2500 psi

On Sole P=100/8 = 12.5psi.

Equal Forces Unequal P

Note force is the same in both cases but the ratio of pressures is 2500/12.5 = 200 to 1!

Mass density (D)

The mass per unit volume of a substance. The mass of a quantity of a substance divided by the volume it occupies.

Mass density = mass/volume

D=m/V = 20kg/2m^{3 =}10kg/m³

D of 2 x 2 x 4 m, 40KG Cube

D=?

M= 40 kg,

Cube of dimensions 2 x 2 x 4 m. V=lwh = 2 x 2 x 4 = 16 cubic meters

D = m/V = 40Kg/ 16 m³ = 2.5 kg/ m³

Weight density (D_w)

The weight per unit volume of a substance. The weight of a quantity of a substance divided by the volume it occupies.

D_w = W/V = Weight/Volume

= 196 N/2 cu.m =98 N/m³

D_w of 2 x 2 x 4 m, 40KG Cube

D_w =?

M= 40 kg, W = 40 x 9.8 = 392 N

Cube of dimensions 2 x 2 x 4 m. V=lwh = 2 x 2 x 4 = 16 cubic meters

D_w = W/V = 392N/ 16 m³ = 24 N/ m³

Specific Gravity

Relation between density of a material and density of water.

Ratio Dx/Dw (Density of x divided by density of water).

What is the Specific Gravity of Concrete?

Density of concrete =2500 kg/m³,

Density of water = 1000 kg/m³.

Specific Gravity of concrete =

Dx/Dw = 2500/1000

= 2.5. Note, no units on sp.gr!

Pressure in Fluids

Pressure increases with depth!

Law of fluid pressure The (gauge) pressure at any depth in a fluid at rest equals the weight of the fluid in a column extending from that depth to the top of the fluid divided by the cross-sectional area of the column.

Law of fluid pressure

The (gauge) pressure at any depth in a fluid at rest equals the weight of the fluid in a column extending from that depth to the top of the fluid divided by the cross-sectional area of the column.

Pressure in Water

Water weighs 62.5 lbs/cu.ft

A cube 1 x 1 x 1 ft has a surface of 1 sq.ft.

At a depth of 1 ft you have 62.5 lbs/sqft pressure

Multiply depth in ft by 62.5 to find P

20 ft, P = 20 x 62.5 = 1250 lbs/sq.ft.

Converting to lbs/sq.in

Gauges usually use lbs/sq.in

1 sq.ft = 12in x 12 in = 144 sq.in.

62.4 lbs/sq.ft = 62.4/144

= .433 lbs/sq.in.

Thus using psi:p=0.433 psi/ft x h(ft)

At 20 ft. P = .433 x 20 = 8.66 psi.

Gauge pressure vs total p

measures difference between inside and outside pressure?

see p. 141 and 142

Buoyant force

The upward force exerted by a fluid on a substance partly or completely immersed in it.

Archimedes' Principle

The buoyant force acting on a substance in a fluid at rest is equal to the weight of the fluid displaced by the substance.

Floating, Sinking, or Rising

Buoyant force greater than weight of object, object floats.

Buoyant force less than weight, object sinks.

Light object released from a submarine rises, if density less than water, otherwise sinks.

Pascal's Principle

Pressure applied to an enclosed fluid is transmitted undiminished to all parts of the fluid and to the walls of the container.

Problem Force from Pressure and Area

Pressure = F/A then F = P x A

Side of can 8 x 10 inches?

Area 8 x 10 = 80 sq in., P=14.7psi

F = 14.7 psi x 80 sq.in. = 1176 lbs

Mass from Density Problem

Dm = M/Vol

M = Dm x Vol

Vol = 2m x 3m x 4m = 24 cu.m

Dm = 11,340kg/cu.m

M = 11,340 x 24 = 272,160 kg.

Buoyant Force Problem

Swimmer’s volume = 2 ft³

Buoyant Force,BF = ?

BF= Wt of water he displaces

= His Vol x density of water (62.4 lbs/ft³⁾

2 ft³ x 62.4 lbs/ft³ = 124.8 lbs

Formulas Chapter 4

p= F/A Pressure is Force divided by area perpendicular to the force

D_m=m/V

Mass density, D_m = mass, m/volume, V

D_w=w/V

Weight Density, D_w = weight, w/volume, V

F_b= W_FD

Archimedes’ Principle: Buoyant Force = Weight of the fluid displaced

Special Case Equations

p=D_wh=D_m x g x h Gauge Pressure, p at a depth h in a liquid of wt density D_wor mass density D_m

p=0.433 (psi/ft) x h(ft) Gauge Pressure in psi underwater at a depth h in feet

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	A vacuum exists in outer space.
	It is the absence of all matter.
	Vacuums are relative
	Even in outer space some matter exists
	But the amount is so small that a person would die if exposed to vacuum without a space suite


	Solid A rigid body, retains its shape unless distorted by a strong force.. Examples: rock, wood, plastic, iron


	Flow readily,
	conform to the shape of their container.
	Have a well defined boundary (surface).
	More dense than gases.
	Examples water, beverages, blood, oil,…


	Flow readily,
	conform to the shape and size of their container,
	do not have a well defined surface,
	can be compressed or expanded readily.
	Examples: air, carbon dioxide, helium, steam.


	An ionized gas, often referred to as the fourth state of matter.
	It consists of positive ions and electrons
	interacts strongly with magnetic fields
	conducts electricity.
	Commonly exists only at higher temperatures or in strong electromagnetic fields
	Examples: Sun, candle flame, gases in operating fluorescent, neon, and vapor lights.


	Greeks described smallest particles of matter as atoms.
	Now we know there are even smaller particles.
	Atoms are composed of
		Electrons, protons and neutrons.
		Protons and neutrons are in the center or nucleus of the atom
		Electrons orbit around the nucleus


	Neutron Electrically neutral particle residing in the nucleus of an atom.
	Proton Positively charged particle residing in the nucleus of an atom.
	Electron Negatively charged particle, usually found orbiting the nucleus of an atom.


	One of over 115 different fundamental substances
	The simplest and purest forms of matter.
	All have the same type of Atom, specifically the same number of protons in the nucleus.
	Scientists are still discovering new elements so the number is always increasing.


	Gold, Silver, Oxygen, Silicon, Nitrogen,….
	Nitrogen is the most abundant element. It makes up about 80% of our air.
	Silicon is also very abundant, since it occurs in sand, a compound of Silicon and Oxygen.


	Two or more atoms combine to form a molecule. If the atoms are different types it is a compound.
	A Compound is something composed of identical molecules of more than one type of atom or element. 2 or more elements combine chemically.
	E.G. SiO₂ Is a compound composed of molecules with Silicon and Oxygen atoms.


	No chemical reaction, thus not a compound
	Parts do not combine uniformly, they just intermix.
	Parts can be recovered individually.
	Example, Instant Cocoa: chocolate, sugar, and milk powder.


	A homogeneous mixture of two or more substances, which may be solids, liquids, gases, or a combination of these
	The parts break down into individual molecules, and intersperse, but do not combine.
	E.G. salt in water-salt water


	A suspension has tiny particles, but many molecules in one particle.
	Not a chemical reaction, thus not a compound
	Their particles are larger than molecules thus not a solution.


	Mayonaise, Gelatin, Butter, Ice Cream Orange Juice
	see http://encyclopedia.thefreedictionary.com/Suspension+(chemistry)


	The force per unit area for a force acting perpendicular to a surface. The force acting on a surface divided by its area.
	P = Force/Area = F/A
	Force on the floor= Weight = 100 lbs
	Area of shoes surface 30 sq.in.
	Pressure on the floor =100/30= 3.33psi


	Heel area = .2x.2in=.04sq.in
	Sole area =2 x 4 in = 8 sq.in.
	Weight=100 lbs.
	On Heel P=100/.04 =2500 psi
	On Sole P=100/8 = 12.5psi.


	Note force is the same in both cases but the ratio of pressures is 2500/12.5 = 200 to 1!


	The mass per unit volume of a substance. The mass of a quantity of a substance divided by the volume it occupies.
	Mass density = mass/volume
	D=m/V = 20kg/2m^{3 =}10kg/m³


	D=?
	M= 40 kg,
	Cube of dimensions 2 x 2 x 4 m. V=lwh = 2 x 2 x 4 = 16 cubic meters
	D = m/V = 40Kg/ 16 m³ = 2.5 kg/ m³


	The weight per unit volume of a substance. The weight of a quantity of a substance divided by the volume it occupies.
	D_w = W/V = Weight/Volume
	= 196 N/2 cu.m =98 N/m³


	D_w =?
	M= 40 kg, W = 40 x 9.8 = 392 N
	Cube of dimensions 2 x 2 x 4 m. V=lwh = 2 x 2 x 4 = 16 cubic meters
	D_w = W/V = 392N/ 16 m³ = 24 N/ m³


	Relation between density of a material and density of water.
	Ratio Dx/Dw (Density of x divided by density of water).


	Density of concrete =2500 kg/m³,
	Density of water = 1000 kg/m³.
	Specific Gravity of concrete =
	Dx/Dw = 2500/1000
	= 2.5. Note, no units on sp.gr!


	Pressure increases with depth!
	Law of fluid pressure The (gauge) pressure at any depth in a fluid at rest equals the weight of the fluid in a column extending from that depth to the top of the fluid divided by the cross-sectional area of the column.


	The (gauge) pressure at any depth in a fluid at rest equals the weight of the fluid in a column extending from that depth to the top of the fluid divided by the cross-sectional area of the column.


	Water weighs 62.5 lbs/cu.ft
	A cube 1 x 1 x 1 ft has a surface of 1 sq.ft.
	At a depth of 1 ft you have 62.5 lbs/sqft pressure
	Multiply depth in ft by 62.5 to find P
	20 ft, P = 20 x 62.5 = 1250 lbs/sq.ft.


	Gauges usually use lbs/sq.in
	1 sq.ft = 12in x 12 in = 144 sq.in.
	62.4 lbs/sq.ft = 62.4/144
	= .433 lbs/sq.in.
	Thus using psi:p=0.433 psi/ft x h(ft)
	At 20 ft. P = .433 x 20 = 8.66 psi.


	measures difference between inside and outside pressure?
	see p. 141 and 142


	The upward force exerted by a fluid on a substance partly or completely immersed in it.


	The buoyant force acting on a substance in a fluid at rest is equal to the weight of the fluid displaced by the substance.