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WELCOME TO Physics 2425-300

WELCOME TO Physics 2425-300. Mr. Kris Byboth. Syllabus. The course syllabus can be found on the web at http://www.blinn.edu/brazos/natscience/phys/kbyboth/. Keys To Success . Don’t get behind Ask a question every time something is unclear!

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WELCOME TO Physics 2425-300

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  1. WELCOME TOPhysics 2425-300 Mr. Kris Byboth

  2. Syllabus • The course syllabus can be found on the web at http://www.blinn.edu/brazos/natscience/phys/kbyboth/

  3. Keys To Success • Don’t get behind • Ask a question every time something is unclear! • Write a formal solution to every problem (learn how to approach problems) • Work more problems (you cannot memorize physics) • Form study groups

  4. What is Physics? • Physics is the study of the laws of nature. • It is the attempt to understand, model, and predict the behavior of the world around us. • This course will emphasize application of mathematical models to physical situations.

  5. Units • Each measurement requires some predefined unit of measure. • Units will often help you identify what variables are being given in a problem.

  6. SI Units Length meter (m) – The distance traveled by light in vacuum in 1/299,792,458 seconds Mass kilogram (kg) – The mass of a specific platinum-iridium cylinder Time second (s) – The period of 9,192,631,770 oscillations the radiation from a cesium-133 atom

  7. Conversions • Converting between units is just multiplying by one. • 7.4ft = ?in • The conversion factor is 1ft = 12 in

  8. Conversion factors to know • 1ft = 12 in • 1in = 2.54cm • 1yd = 3ft • 1mi = 5280ft = 1609m • 1m = 3.281ft • 1hr = 60min = 3600s • 1m = 100cm = 1000mm • 1km = 1000m

  9. Unit Prefixes Prefix Abbreviation Conversion • mega M 106 • kilo k 103 • centi c 10-2 • milli m 10-3 • micro μ 10-6 • nano n 10-9 • pico p 10-12 • Read as 1 (Prefix) = Conversion (unit) • 1kilometer = 103 m = 1000m • 1cm = 10-2 m = 0.01m

  10. Conversion Practice • 4.500yd = ? cm • 411.5cm • 45m2 = ? cm2 • 4.5∙105 cm2 • 55.0mi/hr = ? m/s • 24.6m/s

  11. Significant Figures • An easy way to maintain accuracy in calculations. • All non-zero numbers are significant • Zeros are not significant if they are leading (0.003). • Trailing zeros are significant • 300 – 3 sig figs 0.003 - 1sig fig • 30.0 – 3 sig figs • 010010 -? Sig figs • In scientific notation the integers preceding the ∙10x are significant. • 1.3∙106 -2 sig figs • Conversion factors are assumed to have an infinite number of sig figs.

  12. Mathematical operations with Sig. Figs • When multiplying or dividing keep only the lowest number of significant figures • When adding or subtracting keep only the lowest number of decimal places • 32*2 = 6∙101 32*2.0=64 • 1.3+2.54=3.8 1 - 0.54 = 0 • 0.5*300 = ? 100.2+18.65 = ?

  13. Dimensional Analysis • A check of the possible validity of a formula by comparing the units on each side of the equation.

  14. We notate the dimensionality of a quantity as follows. [x] = L where x is a position • When adding quantities each term must have the same dimensionality If A=B+C then [A]=[B]=[C] • The dimensionality of a product is given as follows [AB]=[A][B] • The dimensionality of a dimensionless constant, κ,is 1. [κ]=1 ex: ½, p

  15. Dimensional Analysis Ex: • Is the following equation dimensionally consistent? • x=xo + v∙t +1/2 a∙t2 • [x] = L, [v] = L/T, [t]=T, [1/2] =1, [a]=L/T 2 L = L + (L/T)T + (L/ T2)T2 L = L + L + L

  16. Example from Conceptual Ex.

  17. Round Off Errors • Round off errors are deviations of a solution (usually but not always small) from the actual solution due to rounding intermediate calculations in route to the final solution. • If possible reduce all problems to an algebraic solution then calculate a numeric answer.

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