DATA

SCIENCE is…SCIENCE is…

the search forthe search forrelationshipsrelationshipsthat that explainexplainand and predictpredict the behavior the behavior of the of the universe.universe.

PHYSICS is…PHYSICS is…

the sciencethe scienceconcerned withconcerned withrelationshipsrelationshipsbetween matter,between matter,energy, and itsenergy, and itstransformations.transformations.

There is no such thing asThere is no such thing asabsolute certaintyabsolute certainty

of a scientific claim.of a scientific claim.

The validity of a scientific conclusion is always limited by:The validity of a scientific conclusion is always limited by:

• the experimentthe experimentdesign, equipment, etc...design, equipment, etc...

• the experimenterthe experimenterhuman error, interpretation, etc...human error, interpretation, etc...

• our limited knowledgeour limited knowledgeignorance, future discoveries, etc...ignorance, future discoveries, etc...

Scientific LawScientific Law

Scientific TheoryScientific Theory

Scientific HypothesisScientific Hypothesis

a statement describing a natural eventa statement describing a natural event

an experimentally confirmed explanationan experimentally confirmed explanationfor a natural eventfor a natural event

an educated guess (experimentally untested)an educated guess (experimentally untested)

developed in France in 1795developed in France in 1795a.k.a. “SI”a.k.a. “SI” -- International System of UnitsInternational System of Units

The U.S. was (and still is) reluctant to “go metric.”The U.S. was (and still is) reluctant to “go metric.”

• very costly to changevery costly to change• perception of “Communist” systemperception of “Communist” system

• natural resistance to changenatural resistance to change• American prideAmerican pride

The SI unit of:The SI unit of:• length is the length is the metermeter, m, m

• time is the time is the secondsecond, s, s

• mass is the mass is the kilogramkilogram, kg., kg.

• electric charge is the electric charge is the CoulombCoulomb, C, C

• temperature is the degree temperature is the degree KelvinKelvin, K, K

• an amount of a substance is the an amount of a substance is the molemole, mol, mol

• luminous intensity is the luminous intensity is the candlecandle, cd, cd

• The The secondsecond is defined in terms of is defined in terms ofatomic vibrationsatomic vibrations of Cesium-133 atoms. of Cesium-133 atoms.

• The The metermeter is defined in terms of the is defined in terms of the speed of lightspeed of light..

• The The kilogramkilogram is still defined by is still defined byan an official physical standardofficial physical standard..

““Derived units” are combinationsDerived units” are combinationsof these “fundamental units”of these “fundamental units”

Examples include Examples include speedspeed in in m/sm/s, , areaarea in in mm22,,forceforce in in kgkg..m/sm/s22, , accelerationacceleration in in m/sm/s22,,

volumevolume in in mm33, , energyenergy in in kgkg..mm22/s/s22

10101818 exaexa E E10101515 petapeta P P10101212 teratera T T 101099 gigagiga G G 101066 megamega M M 101033 kilokilo k k 101022 hectohecto h h 101011 dekadeka da da

10101818 attoatto a a10101515 femtofemto f f10101212 picopico p p 101099 nanonano n n 101066 micromicro 101033 milli milli m m 101022 centicenti c c 101011 decideci d d

Explore the metric systemExplore the metric systemat at link1, link2, and link3.

See definitions of metric units See definitions of metric units here.Click Click here to do conversions.

All measurements have some degree of uncertainty.All measurements have some degree of uncertainty.

PrecisionPrecisionsingle measurementsingle measurement - exactness, definitenessexactness, definiteness

group of measurementsgroup of measurements - agreement, closeness togetheragreement, closeness together

AccuracyAccuracycloseness to the accepted valuecloseness to the accepted value

% error % error == accepted accepted -- observed observed

acceptedaccepted xx 100% 100%

Four student lab groups performed data collection activities in order Four student lab groups performed data collection activities in order to determine the resistance of some unknown resistor (you will do this to determine the resistance of some unknown resistor (you will do this later in the course). Data from 5 trials are displayed below.later in the course). Data from 5 trials are displayed below.

Suppose the accepted value for the resistance is 500 Suppose the accepted value for the resistance is 500 ΩΩ. . Then we would classify each groups’ trials as:Then we would classify each groups’ trials as:

Group 1: neither precise nor accurateGroup 1: neither precise nor accurateGroup 2: precise, but not accurate Group 2: precise, but not accurate Group 3: accurate, but not preciseGroup 3: accurate, but not preciseGroup 4: both precise and accurateGroup 4: both precise and accurate

Example of the differences between precision and Example of the differences between precision and accuracy for a set of measurements:accuracy for a set of measurements:

GroupGroup Trial 1Trial 1 Trial 2Trial 2 Trial 3Trial 3 Trial 4Trial 4 Trial 5Trial 5 avgavg

11 3434 612612 7878 126126 413413 132.6132.6

22 126126 127127 126126 128128 125125 126.4126.4

33 2020 500500 6262 980980 938938 500500

44 502502 501501 503503 498498 499499 500.6500.6

1.1. All non-zero digitsAll non-zero digits are are significantsignificant..

2.2. Zeros between other significantZeros between other significantdigitsdigits are significantare significant..

3.3. Leading zerosLeading zeros are not are not significantsignificant. .

4.4. Final zeros before the decimalFinal zeros before the decimal are not significantare not significant..

Operations with Significant DigitsOperations with Significant Digits

Addition and Subtraction Addition and Subtraction (link)(link)

round the sum or differenceround the sum or differenceto the least precise decimal placeto the least precise decimal place

Multiplication and Division Multiplication and Division (link)(link)

round so that the product or quotientround so that the product or quotienthas a total number of significant digitshas a total number of significant digits

equal to the total number of significant digitsequal to the total number of significant digitsof the least precise quantity of the least precise quantity

Learn more about significant digitsLearn more about significant digitshere and here.

Check your understanding here and Check your understanding here and here.here.

The “bottom line” is that the precision to which aThe “bottom line” is that the precision to which ameasured or calculated amount is written providesmeasured or calculated amount is written providesvaluable information as to the precision (certainty)valuable information as to the precision (certainty)

of that value and the device used to measure it.of that value and the device used to measure it.