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NUMBERS IN PHYSICS

There is no such thing as not being “GOOD” at something, it’s all in your willingness to meet the challenge and not give up. NUMBERS IN PHYSICS. I . Measurements II. Significant Figures. A. Making Measurements. Indicate precision of a measurement. Recording Sig Figs

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NUMBERS IN PHYSICS

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  1. There is no such thing as not being “GOOD” at something, it’s all in your willingness to meet the challenge and not give up.

  2. NUMBERS IN PHYSICS I. Measurements II. Significant Figures

  3. A. Making Measurements • 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

  4. B. Significant Figures • 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 number 2,500

  5. B. Significant Figures Counting Sig Fig Examples 4 sig figs 1. 23.50 1. 23.50 3 sig figs 2. 402 2. 402 3. 5,280 3. 5,280 3 sig figs 2 sig figs 4. 0.080 4. 0.080

  6. B. Significant Figures • 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 YEAR!!! It will always be included as partial credit on all tests.

  7. B. Significant Figures • 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. 224 g + 130 g 354 g 224 g + 130 g 354 g 3.75 mL + 4.1 mL 7.85 mL 3.75 mL + 4.1 mL 7.85 mL  7.9 mL  350 g

  8. 3 SF B. Significant Figures • 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 4 SF 3 SF 324g

  9.  2.4 g/mL 2 SF B. Significant Figures (15.30 g) ÷ (6.4 mL) 4 SF 2 SF = 2.390625 g/mL 18.9 g - 0.84 g  18.1 g 18.06 g

  10. B. Significant Figures • 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

  11. NUMBERS IN PHYSICS III. Scientific Notation IV. Proportions/Graphing

  12. A. Scientific Notation • 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

  13. A. Scientific Notation • A number between 1 and 10 • A power of 10 N x 10x

  14. EXE EXP EXP ENTER EE EE A. Scientific Notation 5.44 × 107 g 8.1 × 104 mol = • Calculating Type on your calculator: 5.44 7 8.1 ÷ 4 = 671.6049383 = 6.7 × 102 g/mol = 670 g/mol

  15. B. Graphing • 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

  16. B. Graphing

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