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PHY 205 Brad Armen

This web page provides a review of the concepts of precision, measurement accuracy, and the use of significant figures in physics. It also includes examples and exercises to practice these concepts.

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PHY 205 Brad Armen

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  1. PHY 205 Brad Armen Class web site: http://webspace.ship.edu/gbarmen/PHY205

  2. Text: Physicsfor Scientists and Engineers … (9thed) By Serway and Jewett

  3. HW: ‘WebAssign’: https://www.webassign.net Our course key: ship 1503 9518 (Adobe flash)

  4. Submit Answer You get 5(?) tries, here’s how to use them wisely. Check math Bad Check thinking Bad Answer Still Wrong Get HELP!

  5. CH.1 Review of some stuff: • Exponents and powers of ten representation: • Precision of physical quantities. • Error and the Sig Fig method. • Units of physical quantities.

  6. Representing Numbers—Powers of 10 25 22 = (2×2×2×2×2) × (2×2) = 25+2 =27

  7. (works for non-integer powers too!) e.g.

  8. Powers of ten are useful/standard:

  9. Powers of ten are useful/standard:

  10. Try this

  11. Try this (12.×1030) = 1.2 × 1031 Standard

  12. Try this

  13. Try this (12.×10-20) = 1.2 × 10-19 Standard

  14. Try this

  15. Try this (0.75×1030) = 7.5 × 1029 Standard

  16. Try this (300,000)+(4,000,000,000,000,000) = 4,000,000,000,300,000 = 4.0000000003 × 1015

  17. Measuring things

  18. Working precision: 1 mm (2 digits)

  19. Working precision: 0.01 mm (3 digits)

  20. Working precision: 0.00001 kW (5.5 digits)

  21. Working precision: 0.000001 V (6.5 digits)

  22. Uncertainty ? (Looks closer to 4.6)

  23. How to report a measurement? Honest but cumbersome: (but Looks closer to 4.6) Easier to work with: Easier yet: “Sig. fig.” notation! Implied uncertainty is

  24. Measurement accuracy Q: How accurate is my measurement? Is it the same as my precision?

  25. A: No! Q: Which one’s correct? What can I do????

  26. A: (certified) copies of standards …

  27. Some industrial examples …

  28. Some industrial examples …

  29. My DMM …. Reading Accuracy:

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