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PHYSICS; here we come!!!!

PHYSICS; here we come!!!!. Stuff we need to know at the beginning!. Significant Figures aka “Sig Figs”. Valid digits in a measurement Example: 8.636 = 4 sig figs Rules: All nonzero digits are significant All final zeros after the decimal point are significant

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PHYSICS; here we come!!!!

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  1. PHYSICS;here we come!!!! Stuff we need to know at the beginning!

  2. Significant Figures aka “Sig Figs” • Valid digits in a measurement • Example: 8.636 = 4 sig figs • Rules: • All nonzero digits are significant • All final zeros after the decimal point are significant • Zeros between other sig. digits are always significant • Zeros as a placeholder are NOT significant How many sig figs? 245m 18.0g 308km 0.00623g

  3. Try these! Sig Figs • 75 m • 75.00 m • 0.007060 kg • 1.87 x 106 mL • 1.008 x 108 m • 1.20 x 10-4 m • 2804 m • 2.84 m • 0.0029 km • 0.003068 m • 4.6 x 105 m • 4.6 x 10-5 m

  4. Add/Subtract/Multiply/Dividewith Sig Figs! • ADD/SUBTRACT • Perform operation and round off to LEAST precise value • Ex: 24.686 + 2.343 + 3.21 = 30.239 round off to 30.2 • MULTIPLY/DIVIDE • Perform operation and round off product or quotient to factor with LEAST # of sig figs • Ex: 3.22 x 2.1 = 6.762  6.8 • 36.5/3.414 = 10.691  10.7

  5. Scientific Notation • Writing large or small measurements by expressing decimal places as powers of 10 (M x 10n) • Exponent of 10 is the # of places the decimal point moved • Examples: sun to Mars 227 800 000 000m 2.278 x 1011 m mass of an electron 0.000 000 000 000 000 000 000 000 000 000 911 kg 9.11 x 10-31 kg

  6. Try these! Sci Not • 5800 m • 450000 m • 302 000 000 m • 0.000508 kg • 0.004 kg • 0.0003600 kg • 93 000 000 s

  7. Add/Subtract/Multiply/Dividewith scientific notation • If numbers have the same exponent (n), add or subtract the values of M, keep same exponent • If exponents are not the same, move decimal to left or right until they are the same- then add or subtract M • Multiply values of M and add the exponents – multiply units • Divide the values of M and subtract the exponent of the divisor from the exponent of the dividend

  8. Try these! Sci Not Operations 6.23 x 106 kL + 5.34 x 107 kL 9.87 x 104 g – 6.2 x 103 g (4.8 x 105 km) * (2.0 x 103 km) (8.4 x 106 L) ÷ (2.0 x 103 L)

  9. Metrics • Seven basic SI units • Base units are based on a physical object or process • length (m - meter), mass (kg - kilogram), time (s - second), electric current (A -ampere), temperature (K - Kelvin), amount (mol - mole), luminous intensity (cd - candela) • Derived units are created by multiplying or dividing the 7 basic units • 1 L = 1 dm3 • 1 mL = 1 cm3 • J = kgm2/s2

  10. Use metric prefixes to convert metric units • giga (G) billion – 109 base units= 1,000,000,000 • mega (M) Million – 106 base units= 1,000,000 • kilo (k) thousand – 103base units = 1,000 • Base unit = 100base units = 1 • deci (d) tenth – 10-1base units = 0.1 • centi (c) hundredth – 10-2base units = 0.01 • milli (m) thousandth – 10-3base units = 0.001 • micro (ų) millionth – 10-6base units = 0.000001 • nano (n) billionth – 10-9 base units = 0.000000001 • pico (p) trillionth – 10-12 base units = 0.000000000001

  11. Conversion • Move decimals to change unit • 5.7 g to milligrams • 45.3 mm to meters • 10 km to centimeters • 783 kg to milligrams • 98 mL to deciliters • Try these! • 4.9 mg = _____g • 7.6 dm = ___mm • 32.1 g = ______ cg • 5.6 X10 3 cm = ___m

  12. Dimensional Analysis • Process to convert units:single or multiple • Lay out given and where you want to go to & get rid of • Insert conversion Ex: 31g to milligrams 31 g (known)= __1000mg (go to) = 31000mg 1 1 g (get rid of)  3.1 x 104 mg! • Multiply across, divide top/bottom, check unit and scientific notation! •  if too big a jump, always pass through the base unit! Put conversion here!

  13. DA Examples: same problem… 3 ways! 285cm to km 285cm =_1__m = __1__km = 285 = 0.00285km 1 100 cm 1000 m 100000  2.85 x 10-3 km 285cm =_1__m = 10-3km = 285 x 10-3 = 285 x 10-5 km 1 102 cm 1 m 1 x 102 2.85 x 10-3 km 285cm =_0.01_m = 0.001km = 0.00285 = 0.00285 km 1 1 cm 1 m 1 2.85 x 10-3 km

  14. A little harder… 66 m/s to km/hr 66 m = 3600s = _1__km = 237600 km = 237.6 1 s 1 hr 1000 m 1000 hr  2.376 x 102 km/hr * Convert each unit separately first…

  15. Accuracy vs. Precision • Accuracy – extent to which a measurement approaches the true value of a quantity • Precision – degree of exactness or refinement of a measurement • Can have: • poor precision & poor accuracy • Good precision & good accuracy • Good precision & poor accuracy • BUT NOT poor precision & good accuracy

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