Introduction, Scientific Method, Measurements

Learning Objectives

• Physical Sciences• Scientific Method• Standard Units• Fundamental and Derived Quantities• Converting Units

Physical Sciences

BIOLOGICAL SCIENCES

PHYSICS CHEMISTRY ASTRONOMY METEOROLOGY GEOLOGY

PHYSICAL SCIENCES

NATURAL SCIENCESSOCIAL SCIENCES

SCIENCES

(Latin scientia meaning knowledge)An organized body of knowledge about the natural Universe, and the processes by which that knowledgeIs acquired and tested

Concerned with the basics principles ofmatter & energy

Deals with thecomposition, structure,and reactions of matter.

Study of the universe, which is the totality of all matter, energy, space,and time.

Study of the atmosphere,from the ground in outerspace.

Science of the planet Earth-its composition,structure, processes,and history.

Scientific Method

The part we seebut do not understand

The part we(think) we understand

The Universe – all which is observableHow can we come to understand theUniverse?

Epistemology: study (or philosophy) of knowledge.

Ways of knowing:

Fideism: acceptance of an idea, theory, or explanation only on the evidence of a “higher authority”. Religious beliefs, based on faith orrevelation.

Science: a systematic method of observation and experimentation. Based on “evidence” and experimental observation

Scientific Method

Measurement:a quantitative observation

Hypothesis: a very tentative, possible

answer or an educated guess

Experiment: an observation of

natural phenomena

carried out in a controlled manner

Theory: a well-tested explanation of a broad segment of naturalphenomena

Scientific revolution of the 1600s was due primarily to an adoptionof the scientific methodby Galileo, Newton, andBoyle.

Ockham’s Razor: Inchoosing between two seemingly valid explanationsof a particular phenomenon, the simpler and more general one ispreferred.

Scientific Method

• Limitations:– Deals only with the natural world and never

invokes supernatural explanations– Does not attempt to answer questions as the

purpose of the universe or life.– These questions are for philosophy and

religion

Scientific MethodBeware of Pseudoscience!Pseudoscience – the dogmatic and irrational belief in an appealing ideathat appears scientific but that is not supported by scientific methods.

* Astrology (from ancient Babylonian culture) * UFO-ology (popular culture and mistrust of government) * “structure –altered water” (commercial quackery)

How can you recognize a pseudoscience?

Science PseudoscienceThe primary goal of science is to achieve a more complete and more unified understanding of the physical world.

Pseudosciences are more likely to be driven by ideological, cultural, or commercial goals.

Most scientific fields are the subjects of intense research which result in the continual expansion of knowledge in the discipline.

The field has evolved very little since it was first established. The small amount of research and experimentation that is carried out is generally done more to justify the belief than to extend it.

Observations or data that are not consistent with current scientific understanding, once shown to be credible, generate intense interest among scientists and stimulate additional studies

Observations or data that are not consistent with established beliefs tend to be ignored or actively suppressed

Scientific explanations must be stated in clear, unambiguous terms.

Pseudoscientific explanations tend to be vague and ambiguous, often invoking scientific terms in dubious contexts.

Mathematical Nature of Science• Newton and Leibniz Calculus• Mathematics is the only language precise enough to

accurately describe the laws of nature. isomorphism • Skills needed for success in this course

– Algebra – Basic Trigonometry – Graphical Analysis

Do not worry about your difficulties in Mathematics. I can assure you mine are still greater. – Albert Einstein

Measurements - UnitsWe need numbers in order to accurately take measurements

• When executing the scientific method we must perform experiments measurements data

• Express measurements using units (i.e. metric units, English units, etc.)

Unfortunately American students must learn both systems!

• Units allow us to describe things numerically

• Measurement standards – a fixed and reproducible value for the purpose of taking accurate measurements

How do we know the length of a meter, yard?

• Human arm, standard for length, cubit – Egyptians

• King Loius XIV, length of the royal foot

• Distance from equator to north pole

• Modern standard, distance light,travels in 1/299,792,458 s

The sizes of things:

What does 1025 mean?What does 102 mean?102 = 10 10 = 100

notice that the 2 tells ushow many zeros there are in the answer!

10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 = 10,000,000,000,000,000,000,000,000

What does 10 -25 mean?What does 10 -2 mean?10 -2 = 0.1 0.1 = 0.01

notice that the -2 tells ushow many places to the left we move the decimalpoint!

0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 = 0.0000000000000000000000001

This type of notation is called “scientific notation” it is used to representvery large and very small numbers in a manner that is efficient and easy to do.

Units• Mass: the kilogram

– One kilogram is the mass of a particular platinum-iridium cylinder kept at the International Bureau of Weights and Standards, Sèvres, France.

one kilogram weighs slightly less than one kilogram

Units• Time: the second

– One second is the time for radiation from a cesium-133 atom to complete 9,192,631,770 oscillation cycles.

Units• Fundamental units – fundamental because they are the

most basic quantities or properties– Length (International System, SI meter (m), British foot (ft))– Mass (SI gram (gr), British slug (sl))– Time (SI & British second (s))

• Derived units – combinations of fundamental units– Speed (SI m/s, British ft/s)– Acceleration (SI m/s2, British ft/s2)– Force = mass × acceleration (SI kg·m/s2 = Newton (N),

British pounds (lbs)

Derived Unit

Quantity MKS CGS

Area Length2 m2 cm2

Volume Length3 m3 cm3

Velocity Length/Time m/s cm/sDensity mass/volume =

mass/Length3kg/m3 gr/cm3

Acceleration Length/Time2 m/s2 cm/s2

Force mass Acceleration =mass Length/Time2

(kg m)/s2 (gr cm)/s2

Pressure Force / Area = (mass

Length/Time2)/Length2

[(kg m)/s2]/m2

[(gr cm)/s2]/cm2

UnitsMKS : Meter-Kilogram-SecondCGS: Centimeter-Gram-Second

Sometimes even the derived units are called different names because they are so cumbersome. Typically these units are named after a scientist that contributedto it’s origin.

Force = mass Acceleration = (kg m)/s2 = NEWTON

Converting Units of Measurement – Dimensional Analysis• It is often the case that we must convert from one set of units to another.• Suppose we want to convert 316 ft to its equivalent in meters

metercm

inchcm

milefeet

footinches

kmmile

meterskm

1100

1542

15280

112

1620

10001 ..

Example: How many kilometers is 50,000 inches?

kilometerskilometersxxxx

milekilometer

feetmile

inchesfootinches

27162052801211100050

6201

52801

12100050

..

,

.,

The order that you apply the conversions makes no difference in the end!

these cancel !

left with the units wewant !

DOWNSLOWYESmphhourkilometer

milesmeters

kilometerssm

!3.221

sec36001

62.010001/10

Converting Units of Measurement – Dimensional Analysis

meter

cminchcm

milefeet

footinches

kmmile

meterskm

1100

154.2

15280

112

162.0

10001

If I drive 10 m/s in a school zone posted 20 miles/hour, am I speeding? Here we must convert two things: meters to miles, and secondsto hours

Conversions are a breeze with the metric system because it is based on powersof 10!

Converting Units of Measurement – Dimensional Analysis

Prefix Power ExamplesKilo- 1000, 103 Kilometer, Kiloliter, Kilogram

Hecto- 100, 102 Hectometer,Hectoliter,Hectogram

Deca- 10, 101 Decameter,Decaliter,Decagram

m, l, gr 1, 100 meter,liter,gram

Deci- 0.1, 10-1 Decimeter,Deciliter,Decigram

Centi- 0.01, 10-2 Centimeter,Centiliter,Centigram

Milli- 0.001, 10-3 Millimeter,Milliliter,Milligram

What if I had 10 milliliters and needed to convert this to kiloliters?

kLkLL

kLmLLmL 510100001.01000

11000

110

Prefix Power ExamplesKilo- 1000, 103 Kilometer, Kiloliter, Kilogram Kind

Hecto- 100, 102 Hectometer,Hectoliter,Hectogram Hector

Deca- 10, 101 Decameter,Decaliter,Decagram Decked

m, l, gr 1, 100 meter,liter,gram Mr.

Deci- 0.1, 10-1 Decimeter,Deciliter,Decigram Deci

Centi- 0.01, 10-2 Centimeter,Centiliter,Centigram Cinema

Milli- 0.001, 10-3 Millimeter,Milliliter,Milligram Monday

Converting Units of Measurement – Dimensional Analysis

Kind Hector Decked Mr. Deci at the Cinema on Monday.

K H D M D C M Each word represents one of the powers of ten in themetric system!!

Converting Units of Measurement – Dimensional Analysis

K H D M D C MSo let’s look at how this works using the example we just did.

What if I had 10 milliliters and needed to convert this to kiloliters?

K H D M D C M

10.0 mL = ?? kL

K H D M D C M

Notice that I had to move over 6 letters to get to the “K” (or Kilo). So this corresponds to the number (and direction) of spaces I have to move my decimal!

10.0 mL = 0.00001 kL

Let’s try another example! Go to H-ITT Question

Converting Units of Measurement – Dimensional Analysis

meter

cminchcm

milefeet

footinches

kmmile

meterskm

1100

154.2

15280

112

162.0

10001

We can use converting units to solve some neat problems.

How about this. If I know that a stack of 1,000 - $1 bills is = 1 inch in height

Could I jump over $1,000,000?

Where would we start?

dollarsinchdollars 1000

1000,000,1

ftinchesft

dollarsinchdollars 8312

11000

1000,000,1

???

Dimensional Analysis• Any valid physical formula must be dimensionally

consistent – each term must have the same dimensions

From the table:

Distance = velocity × time

Velocity = acceleration × time

Energy = mass × (velocity)2