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PHYSICS UNIT 0: FOUNDATIONS

PHYSICS UNIT 0: FOUNDATIONS. MEASUREMENT. Units of Measure - Metric System (SI) Fundamental Units : defined by scientists Dimension Unit Symbol length meter m mass kilogram kg time second s current ampere A temperature Kelvin K

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PHYSICS UNIT 0: FOUNDATIONS

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  1. PHYSICS UNIT 0: FOUNDATIONS

  2. MEASUREMENT • Units of Measure - Metric System (SI) • Fundamental Units: defined by scientists Dimension Unit Symbol length meter m mass kilogram kg time second s current ampere A temperature Kelvin K • Derived Units: combinations of fundamental units • ex: area measured in m2, density measured in g/cm3

  3. Measurement • Important Ranges of Magnitudes to remember • Distances – size of a nucleus(10^-15 m) to size of the universe (10^25 m) • Masses – mass of an electron(10^-30 kg) to mass of the universe (10^53 kg) • Times – time for light to pass a nucleus (10^-23 s) to age of the universe (10^18 s) • So what are the order of magnitude differences?

  4. MEASUREMENT • prefixes: for larger or smaller quantities Prefix Symbol Value Example Giga G 109 30 Gb = 30,000,000,000 b mega M 106 2.1 Mm = 2,100,000 m kilo k 103 3.5 kg = 3500 g deci d 10–1 8.7 dL = 0.87 L centi c 10–2 5.9 cs = 0.059 s milli m 10–3 7.2 mmol = 0.0072 mol microm10–6 4.4 mm = 0.0000044 m nano n 10–9 9.0 ng = 0.000000009 g

  5. MEASUREMENT • conversions from one prefix to another: mega kilo none deci centi milli micro nano 1000 1000 10 10 10 1000 1000 larger units smaller units dividemultiply

  6. MEASUREMENT • conversion factors - multipliers that change units without changing equation’s overall value (factors have a value of 1) • ex: 1 in = 2.54 cm factors: • set up so units cancel • ex:find the kilometers in 1 mile

  7. MATHEMATICS • Scientific Notation: shorthand for large & small numbers • form: 0.00 × 10 0(number ≥ 1 & < 10 × power of 10) • ex: 450,000,000 = 4.5 × 100,000,000 = 4.5 × 108 • 0.0000036 = 3.6 × 0.000001 = 3.6 × 10–6

  8. EE 5 8 . 4 EE . 6 3 6 +/- MATHEMATICS • Scientific Calculators • 4.5 × 108 is entered and may appear as or • 3.6 × 10–6 is entered and may appear as or • some calculators use instead of 4.5 08 4.5 08 3.6 -06 3.6 -06 EE EXP

  9. UNCERTAINTY • Significant Figures • shorthand way of showing precision & uncertainty • number of sig. fig's = # of digits BUT don't count beginning zeroes AND don't count ending zeroes unless there is a decimal. 234.15 14.080 560,000 0.00282 5.6 × 105

  10. UNCERTAINTY • Significant Figures • calculations cannot be more exact than measurements: • a. round off to least number of sig. fig's ex:(1.05)(39.04)(251,000)(0.0044)=45271.565 round off to 2 sig. fig's = 45,000 • b. round off once, at the end of all calculations • c. when in doubt, round to 3 sig. fig's

  11. PHYSICS UNIT 0: FOUNDATIONS

  12. The 2 Major Types of Error in Experimental Physics • Systematic Error- Errors inherent in the system of data taking. (Can not be cancelled with lots of data) • Example – using an uncalibrated scale. • Random Error- are inherently unpredictable. (Can be cancelled out with lots of data) • Example – stopping a stop watch too early sometimes and too late other times.

  13. Systematic Error • There are 3 major types of systematic error • human error: mistakes in reading & recording • make repeat measurements (Do not include in lab write up, instead fix human problem). • method error: mistakes in measurement methods • choose the best method & use it consistently. • instrument error: mistakes due to damaged instruments • check instrument calibration, use carefully.

  14. UNCERTAINTY • Accuracy- the degree of closeness of experimental result with theoretical result. (Low systematic error) • Assessing accuracy: percent error(if you know what the measurement should have been by other methods)

  15. UNCERTAINTY • Precision: limitations of a measuring instrument (Sensitivity) • the more digits you can read, the more precision (less uncertainty) • A precise measuring device will take repeated measurements that are close to each other.

  16. GRAPHING • purpose: finding patterns & relationships • drawing graphs: • title graph • dependent variable: y, independent variable:x • Uncertainty in data should be included on graph • Include the equation that best fits the data • choose & show scale on each axis - fit all data • label each axis: measured quantity & units

  17. graph interpretation: linear relationship: as x increases, y increases (y  x) y = mx+b m: slope, b:y-intercept Said “The distance traveled by a car moving at constant speed is directly proportional to the time travelled.”. GRAPHING

  18. graph interpretation: quadratic relationship: as x increases, y increases (y  x2) y = kx2 k: appropriate constant Said “The bacteria population grew exponentially with time.” GRAPHING

  19. graph interpretation: inverse relationship: as x increases, y decreases (y  1/x) y = k/x k: appropriate constant Said “For any given constant force acting on an object there is an inverse relationship between and object’s mass and it’s acceleration” GRAPHING

  20. UNIT 0 QUIZ PREVIEW • Concepts Covered: • metric system: units, prefixes & conversions • accuracy, precision & significant figures • math skills – algebra, scientific notation, estimation, types of graphs. • What’s On The Quiz: • __ multiple choice/matching • __ problems

  21. Equations for Propagating Error Sum Difference Product Quotient

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