TOPIC 1: PHYSICS AND MEASUREMENT IB SL PHYSICS GARCIA GOHS
TOPIC 1. 1: The Realm of Physics • Magnitude: • Estimations of size, often using powers of ten. • Useful when dealing with very large/small amounts • Make comparisons to known amounts
Magnitude exercises • How high is a two-story house in meters? • Solution: • How high is the ceiling compared to you? • How tall are you? • Approx. height of room then multiply by two.
1. 2 Measurement and Uncertainties • S. I. system of measurement • “Systeme International” • Fundamental: base units • Derived: two or more base units combined
1. 2 Measurement and Uncertanties • • Units Metric system Accuracy vs. Precision Significant Figures in calculations
Fundamental SI units
Derived SI units Name Symbol Concept Broken down to base units Newton N Force or weight Kgms-2 Hertz Hz Frequency 1/s or s-1 Joule J Energy or work Kgm 2 s-2
Conversion Factors • Conversion Factor: ratio of equal units to convert from one unit to the other. • 4 quarters/1 dollar = 1; etc… • Factor Label Method: units used for mathematical conversion of measurements • 12 dollars (4 quarters/1 dollar) = ? • Answer = 48 quarters
Converting Units • To convert units: • Measured Amount (Conversion Factor) = New Unit
Metric Prefixes
Using Metric Conversion Factors • When using the metric table for conversion factor remember: • The base unit gets the exponent (base unit is the unit without a prefix) • The prefix gets the number 1 • Example: • 9 m ? mm • Chart says 10 -3 milli • Convert: 9 m (1 mm/10 -3 m) = 9000 mm
Uncertainty and Error • Accuracy: how close a measurement is to the accepted value. • Precision: is the degree of exactness of a measurement; consistency in measurement. • Uncertainty: the measure of confidence in a measurement. A lower uncertainty indicates greater confidence.
Significant Figures (Sig Figs) Determining Sig Figs: Garcia paraphrase 1. All nonzero digits are significant 2. Zero is significant IF: a. Between nonzero digits b. Right of nonzero digits AND there’s a decimal in the number
Sig Figs cont. Addition & Subtraction: • Keep the least accurate decimal place. Example: 1) 25. 1 + 2. 03 = 27. 1 2) 5400 + 365. 5 = 5766
Sig Figs cont. Multiplication and Division • Keep the least significant figures Example: 3. 05 g/8. 470 m. L = 0. 36009445 g/m. L = 0. 360 g/m. L • Conversion factors are not included for sig figs
Scientific Notation • Used to represent large or small numbers • General form: M x 10 n • 1 < M < 10 • n is an integer (+ or - whole number) • Example: • 60200000000000 = 6. 02 x 1023
Graphing • Practice to come later.
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