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Measurement Principles

Measurement Principles. If you cannot measure it, then it is not science. —Lord Kelvin. An experiment is a question which science poses to Nature, and a measurement is the recording of Nature's answer. — Max Planck. Modern examples of why we should be careful when making measurements!.

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Measurement Principles

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  1. Measurement Principles If you cannot measure it, then it is not science. —Lord Kelvin An experiment is a question which science poses to Nature, and a measurement is the recording of Nature's answer. — Max Planck

  2. Modern examples of why we should be careful when making measurements! Mars Climate Orbiter Gimli Glider • 1983 this Boeing 767 ran out of fuel due to an error converting gallons to litres! • 1999 NASA lost this orbiter due to a mismatch in units (metric and imperial)

  3. Measurement topics: Days 1-2: • Measurement Error • Uncertainty and significant digits • Precision and accuracy • Weakest link rules –combining measurements Day 3: Metric system and units conversion • Relationship between variables • Day 4-5: Simple Pendulum lab (formative)

  4. Measurement uncertainty and Significant digits • Record all certain digits in a measurement plus last estimated or uncertain digit • E.g. a length of 10.2 ± 0.1 cm state measurement error • All of the digits in this measurement are significant!

  5. Significant Digits: All digits in a measured number are significant EXCEPT: ●leading zeros for decimal numbers (as they are placeholders) ●trailing zeros for whole numbers (as they are placeholders) Counted Values are considered EXACT (infinite significant digits) Examples: 3 sig digs 6.05 kg : ________________ 0.1255 s : ________________ 4 sig digs 120 m : ________________ 2 sig digs 60.00 mL : ________________ 4 sig digs Infinite sig digs 30 students: ________________ 0.0025 g: ________________ 2 sig digs

  6. Accuracy versus Precision Accuracy: refers to how closely measurement agrees with the “true” value Precision : refers to the resolution with which a measurement is made

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