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Corresponds to “Chapter 3” & “Appendix C: Math Handbook” (pgs R56-63)
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Measurement A quantity that has both a NUMBER and a UNIT ▪ Units are metric* Scientific Notation Product of a coefficient and 10 raised to a power ▪ Coefficient must be 1 ≤ # ≥ 9 ▪ 10 0 = 1 ▪ 10 1 = 10 ▪ Use “EE” or “EXP” or “E” button ▪ means “times 10 to the”
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Accuracy Measure of how close a measurement comes to the actual or true vale of whatever is measured ▪ How close to the bulls-eye did your dart(s) land? Precision Measure of how close a series of measurements are to one another ▪ How close together are all your darts? (regardless of proximity to bulls-eye)
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EError = experimental value – accepted value EExp value = measured in lab AAccepted value = correct value based on reliable references or formulas %% error = l error l x 100 % accepted ▪%▪% error = (the absolute value of exp – accepted) divided by the accepted value, times 100 to make it a %
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ALL “known” digits + 1 “estimated” digit Known are digits clearly marked by instrument increments Estimated is the smallest increment divided by 10 ▪ So if ruler marks off millimeters (0.001 m) then the unknown digit will be the ten-thousandths’ place (0.0001 m)… or 0.1 mm Sig figs can be annoying, but it is important to only record measurements to the most or least precise it can be… ▪ Think adding exactly 1.00mL from an eye-dropper to a gallon of fluid… why bother taking the time to be perfect with the 1.00mL?
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All nonzero digits are significant 1998 m = 4 sig figs Embedded zeros are significant 2002 L = 4 sig figs Leading zeros are NOT significant 0.08 g = 1 sig fig ▪ (because could be written as 8 X 10 -2 g…clearly 1 sig fig) Trailing zeros are NOT sig, UNLESS a decimal point is involved 2010 mg = 3 sig figs, BUT 201.0 cg = 4 sig figs; 2010. mg = 4 sig figs ▪ although that format is frowned upon because it could and should be written as 2.010 x 10 3 mg (obviously 4 sig figs still)
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Counted numbers 24 students in the classroom 5 “digits” on my hand Defined quantities 60 minutes = 1 hour 100 pennies = 1 dollar 100 cm = 1 m
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IIf digit ≤4, truncate (drop) 22.22 cm 2.2 cm IIf digit > 5, round up 11.68 cm 1.7 cm IIf digit = 5, look at numbers after OR before IIf there is a NONZERO digit AFTER a 5, round the 5 up (ex: 1.251 cm 1.3 cm) IIf there is a ZERO or NO DIGIT after a 5, look at the digit BEFORE ▪I▪If digit is EVEN, truncate 5 (ex: 1.250 cm 1.2 cm) ▪I▪If digit is ODD, round up (ex: 1.15 cm 1.2 cm)
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A calculated answer can NEVER be more precise than the least precise measurement from which it is calculated Think eye-dropper into gallon again Think “a chain is only as strong as its weakest link” Addition & Subtraction Keep the LEAST number of DECIMAL PLACES ▪ 1.8 mL + 2 mL = 3.8 mL 4 mL (must round to “ones”) Multiplication & Division Keep the LEAST number of SIGNIFICANT FIGURES ▪ 1.8 m X 2.71 m = 4.878 m 2 4.9 m 2 (must round to 2 figures) ▪ Yes, PEMDAS is still in effect
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Based on powers of 10 Common units [with prefixes if needed] Meter (length) Gram (mass) Second (time) Liter (volume) ▪ If measuring a large item, use a larger unit ▪ If measuring tiny item, use a smaller unit
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kilo- khecto- 1000 10 3 hdeka- 100 10 2 dam, L, g 10 10 1 Basic Unit deci- 10 0 dcenti- 0.1 10 -1 cmilli- 0.01 10 -2 m 0.001 10 -3
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Used to convert the same quantity of something to a new unit Ex: 1 mL = 1 cm 3 (or 1 cc)
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