DATA
SCIENCE is… the search for relationships that explain and predict the behavior of the universe.
PHYSICS is… the science concerned with relationships between matter, energy, and its transformations.
There is no such thing as absolute certainty of a scientific claim. The validity of a scientific conclusion is always limited by: the experiment design, equipment, etc... the experimenter human error, interpretation, etc... our limited knowledge ignorance, future discoveries, etc...
an experimentally confirmed explanation Scientific Law a statement describing a natural event Scientific Theory an experimentally confirmed explanation for a natural event Scientific Hypothesis an educated guess (experimentally untested)
perception of “Communist” system natural resistance to change developed in France in 1795 a.k.a. “SI” - International System of Units The U.S. was (and still is) reluctant to “go metric.” very costly to change perception of “Communist” system natural resistance to change American pride
The SI unit of: length is the meter, m time is the second, s mass is the kilogram, kg. electric charge is the Coulomb, C temperature is the degree Kelvin, K an amount of a substance is the mole, mol luminous intensity is the candle, cd
“Derived units” are combinations of these “fundamental units” The second is defined in terms of atomic vibrations of Cesium-133 atoms. The meter is defined in terms of the speed of light. The kilogram is still defined by an official physical standard. “Derived units” are combinations of these “fundamental units” Examples include speed in m/s, area in m2, force in kg.m/s2, acceleration in m/s2, volume in m3, energy in kg.m2/s2
1018 exa E 1015 peta P 1012 tera T 109 giga G 106 mega M 103 kilo k 102 hecto h 101 deka da 10-18 atto a 10-15 femto f 10-12 pico p 10-9 nano n 10-6 micro m 10-3 milli m 10-2 centi c 10-1 deci d
Explore the metric system at link1, link2, and link3. See definitions of metric units here. Click here to do conversions.
Precision Accuracy % error = x 100% accepted - observed accepted All measurements have some degree of uncertainty. Precision single measurement - exactness, definiteness group of measurements - agreement, closeness together Accuracy closeness to the accepted value accepted - observed accepted % error = x 100%
Example of the differences between precision and accuracy for a set of measurements: Four student lab groups performed data collection activities in order to determine the resistance of some unknown resistor (you will do this later in the course). Data from 5 trials are displayed below. Suppose the accepted value for the resistance is 500 Ω. Then we would classify each groups’ trials as: Group 1: neither precise nor accurate Group 2: precise, but not accurate Group 3: accurate, but not precise Group 4: both precise and accurate Group Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 avg 1 34 612 78 126 413 132.6 2 127 128 125 126.4 3 20 500 62 980 938 4 502 501 503 498 499 500.6
1. All non-zero digits are significant. 2. Zeros between other significant digits are significant. 3. Leading zeros are not significant. 4. Final zeros before the decimal are not significant.
Addition and Subtraction (link) Operations with Significant Digits Addition and Subtraction (link) round the sum or difference to the least precise decimal place Multiplication and Division (link) round so that the product or quotient has a total number of significant digits equal to the total number of significant digits of the least precise quantity
Learn more about significant digits here and here. Check your understanding here and here. The “bottom line” is that the precision to which a measured or calculated amount is written provides valuable information as to the precision (certainty) of that value and the device used to measure it.