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Intro

Mixture of lecture, problems, activities

DRG

 

References:   I will not cover the material necessarily in the format that it is presented in any given textbook or handout.  I will present important ta topics and relationships and leave material to be learned outside of class.

Today you should start reading.  Research areas that are unclear.  Broaden the information in your favorite resource by looking at other material

 

Lec1.ppt

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GOAL: Truly Understand

Understanding cannot be a set of disparate facts that are recalled in a haphazard way to make predictions.  They must be a linked map that allows one to reach the same conclusion no matter how one proceeds.

 

Road map as a set of facts

Harrisonburg is north of Staunton

Harrisonburg is north of Lexington

 

Understanding links the facts requiring Staunton to be in between. Facts are linked to make a complete and consistent picture.  Also previous experiences and relationships are incorporated, driving from Lexington to Staunton is like driving from Staunton to Harrisonburg except a bit longer and through a few more hills ….

 

 

Ask questions

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How people learn slides

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UNITS

SI are the standard but not the only important

Temperature  oC,  oF

Math or algebra of units

Scientific notation

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Math

Trigonometry (sine, cosine  Pythagoras’s theorem)

Algebra  equations

Geometry angle definitions

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SOLID LIQUID GAS

 

 

 

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PRESSURE

Force is a push or a pull.

Physics tells us that these interactions between objects result in motion.

(in physics motion doesn’t mean not moving it encompasses all possibilities including at rest as a state of motion) This a way to get confused because English useage refers to objects at rest as not moving.

 

Pressure is a force per unit area.

 

Weight is a nice force and it provides us with some reference.  We can pile a stack of books up. With each new book we increase the weight. To support this weight we can stack the books on top of a set of poles or blocks (legs of a chair).  The one could refer to the force needed per leg or pole or block.  The walls of a space ship must be able to keep the air inside (imagine a balloon). The trick thing about pressure is that it acts in every direction. A piece of paper  has a balance of pressure on each side. When you ride in an air plane you can equalize pressure and relieve pain.

 

WHAT IS PRESSURE
WHAT ARE UNITS

 

 

 

Pressure Units

Kgf = force on the earth that a KG exerts (weight=mg)

 


pascal
(Pa)


bar
(bar)

technical atmosphere
(at)


atmosphere
(atm)


torr
(Torr)

pound-force per
square inch

(psi)

1 Pa

≡ 1 N/m2

10−5

1.0197×10−5

9.8692×10−6

7.5006×10−3

145.04×10−6

1 bar

100,000

≡ 106 dyn/cm2

1.0197

0.98692

750.06

14.5037744

1 at

98,066.5

0.980665

≡ 1 kgf/cm2

0.96784

735.56

14.223

1 atm

101,325

1.01325

1.0332

≡ 1 atm

760

14.696

1 torr

133.322

1.3332×10−3

1.3595×10−3

1.3158×10−3

≡ 1 Torr; ≈ 1 mmHg

19.337×10−3

1 psi

6.894×103

68.948×10−3

70.307×10−3

68.046×10−3

51.715

≡ 1 lbf/in2

 

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Other properties:

Hardness

Pliability (paper, rubber)

Strength

Divisibility

REACTIONS

Early studies tried to address the quantities of material involved.

Properties of gases

Mix readily

Sometimes the react hydrogen and oxygen turn into water. A large volume of each turns into a small volume of water

 

 

 

1 mole of a gas is about 22 liters

Combining oxygen and hydrogen we have about 50 liters of material

OVER SIMPLIFYING = 1 mole of water

1 mole of water = 18 grams

Water has a density of 1 gm per cubic cm

1 liter is 1000 cc

 

These properties and reactions are grealy simplified when we understand.

ELECTRIC FORCE

ATOMIC NATURE

QUANTUM STRUCTURE  (non intuitive, at least at first)