NUMBERS IN PHYSICS
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Transcript of NUMBERS IN PHYSICS
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I. MeasurementsII. Significant Figures
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Indicate precision of a measurement.
Recording Sig Figs◦ Sig figs in a measurement include the known digits
plus a final estimated digit
2.35 cm
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Significant Figures (sig figs/sig digs)
◦ All non-zero numbers are significant
◦ Zeros:
If the decimal is in the number 0.0025
0.002500
If there is no decimal point in the number2,500
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4. 0.080
3. 5,280
2. 402
1. 23.50
Counting Sig Fig Examples
1. 23.50
2. 402
3. 5,280
4. 0.080
4 sig figs
3 sig figs
3 sig figs
2 sig figs
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Calculating with Sig Figs◦A calculated answer cannot be more
precise than the worst measurement. ◦Significant figures are needed for final
answers when you do any calculating.
THIS WILL BE TRUE FOR THE ENTIRE THIS WILL BE TRUE FOR THE ENTIRE YEAR!!!YEAR!!!
It will always be included as partial credit on all It will always be included as partial credit on all tests.tests.
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Calculating with Sig Figs (con’t)◦ Add/Subtract - The # with the lowest decimal value
determines the place of the last sig fig in the answer.
3.75 mL
+ 4.1 mL
7.85 mL
224 g
+ 130 g
354 g 7.9 mL 350 g
3.75 mL
+ 4.1 mL
7.85 mL
224 g
+ 130 g
354 g
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Calculating with Sig Figs◦ Multiply/Divide - The # with the fewest sig figs
determines the # of sig figs in the answer.
(13.91g/cm3)(23.3cm3) = 324.103g
324 g
4 SF 3 SF3 SF
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(15.30 g) ÷ (6.4 mL)
= 2.390625 g/mL
18.1 g
18.9 g
- 0.84 g18.06 g
4 SF 2 SF
2.4 g/mL2 SF
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Calculating with Sig Figs (con’t)◦ Exact Numbers do not limit the # of sig figs in the
answer. Counting numbers: 12 students Exact conversions: 1 m = 100 cm “1” in any conversion: 1 in = 2.54 cm
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III. Scientific NotationIV. Proportions/Graphing
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Put your calculator in SCI mode (easiest)
Converting into Sci. Notation:
◦ Move decimal until there’s 1 digit to its left. Places moved = exponent.
◦ Large # (>1) positive exponentSmall # (<1) negative exponent
◦ Only include sig figs.
65,000 kg 6.5 × 104 kg
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A number between 1 and 10
A power of 10
N x 10x
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Calculating5.44 × 107 g
8.1 × 104 mol =
5.44EXPEXP
EEEE ÷÷EXPEXP
EEEE ENTERENTER
EXEEXE7 8.1 4
= 671.6049383
= 670 g/mol = 6.7 × 102 g/mol
Type on your calculator:
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Graph data to find patterns more easily
Look for easy things like smooth lines and curves
Slopes give us constants y=mx + b Area under the curve can represent values we are looking for
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