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Measuring

Measuring. Measuring. Measuring. MKS system. MKS – Meter-Kilogram-Second. Historical Pt-Ir meter bars. U.S. National Kilogram (NIST). Cesium Fountain Clock at NIST. Seven Fundamental units Kilogram Meter Second Candela Ampere Kelvin Mole. Giga (G) = 10 9 Mega (M) = 10 6

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Measuring

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  1. Measuring

  2. Measuring

  3. Measuring

  4. MKS system MKS – Meter-Kilogram-Second Historical Pt-Ir meter bars U.S. National Kilogram (NIST)

  5. Cesium Fountain Clock at NIST

  6. Seven Fundamental units Kilogram Meter Second Candela Ampere Kelvin Mole

  7. Giga (G) = 109 Mega (M) = 106 kilo (k) = 103 hecto (h) = 102 deka (da) = 101 deci (d) = 10-1 centi (c) = 10-2 milli (m) = 10-3 micro (m) = 10-6 nano (n) = 10-9 pico (p) = 10-12

  8. The Metric System Examples: 1 km = 1 X 103 m 1 nm = 1 X 10-9 m 1 Ms = 1 X 109 s 1 mL = 1 X 10-3 L

  9. The Metric System Examples: 600 nm = ? m 0.0055 Gs = ? s 5677 kg = ? g

  10. The Metric System Examples: 600 nm = 6 X 10-7 m 0.0055 Gs = 5.5 X 106 s 0.000567 kg = 5.67 X 106 g

  11. Metric Examples • How many meters is 55 cm? • How many milliters is 0.0250 liters? • How many kilograms is 13405 mg? (0.013405 kg) • How many milliseconds is 0.0450 hectoseconds? (4500 ms)

  12. Metric Practice Examples 4658 cm = ? km 635 cm = ? dam 553 ms = ? ds 0.0023 kL = ? mL 0.468 cm = ? mm 7200 cs = ? das 3498 s = ? hours

  13. Metric Practice Examples 4658 cm = 0.04658 km 635 cm = 0.635 dam 553 ms = 5.53 ds 0.0023 kL = 2300 mL 0.468 cm = 4.68 mm 7200 cs = 7.2 das 3498 s = 0.9717 hours

  14. Metric Example 5 How many square meters is 685 cm2? 685 cm2 1 X 10-2 m 1 cm 685 cm2 1 X 10-2 m 1 X 10-2 m 1 cm 1 cm 685 cm2 1 X 10-2 m 1 X 10-2 m = 0.0685 m2 1 cm 1 cm

  15. Metric Example 6 How many square decimeters is 0.250 m2? 0.250 m2 1 dm 1X10-1 m 0.250 m2 1 dm 1 dm 1X10-1 m 1X10-1 m 0.250 m2 1 dm 1 dm = 25.0 dm2 1X10-1 m 1X10-1 m

  16. Metric Example 7 How many cubic centimeters (cm3) is 0.00453 m3? (Ans: 4520 cm3)

  17. Challenge Problem The tallest building in the world is the Burj Kalifa, Dubai. It is 828 meters tall. How many feet is that? (1 inch = 2.54 cm)

  18. Metric Example 9 Convert 22 miles/hour to m/s. 22 miles 1.61 km 1X103m 1 hr 1 min = 9.8 m/s 1 hr 1.00 mile 1 km 60 min 60 s

  19. Metric Example 10 Convert 200 cm/s to miles/hour. 200 cm 1X10-2 m 1 km 1.00 mile 60 s 60 min 1 s 1 cm 1X103 m 1.61 km 1 min 1 hr = 4.47 miles/hr

  20. Metric Practice Examples 55 mi/hr  km/hr 55 mi/hr  meters/min 65 miles/hr  meters/s 400 cm/s  miles/hr

  21. Metric Practice Examples 55 mi/hr  89 km/hr 55 mi/hr  1476 meters/min 65 miles/hr  29.1 meters/s 400 cm/s  8.94 miles/hr

  22. Accuracy and Precision Accuracy • how close the average of a set of measurements is to the true value • Measured using Percent Error % Error = Experimental – Accepted X 100 Accepted

  23. Precision • How close a set of measured values are to one another • Measured using Range • Highest - lowest

  24. Accuracy and Precision Students did trials to measure the density of a metal. The accepted density is 7.2 g/cm3. Were they accurate or precise? Set 1 7.21 7.25 7.18 Set 2 6.40 7.90 7.30 Set 3 6.45 6.52 6.48

  25. Example 1 A student measures the melting point of a sample of beryllium and does four trials. The trials result in melting points of 1267 oC, 1245 oC, 1270 oC, 1255 oC. Calculate the range and comment on precision. Also calculate the percent error (accepted = 1278 oC.)

  26. Error Analysis: Range Example 2 A student measures the density of a sample of lead and does four trials. The trials result in densities of 11.3, 10.5, 11.9, 10.8 g/cm3. The accepted density of lead is 11.4 g/cm3. Comment on accuracy and precision.

  27. Scientific Method A. Hypothesis – untested, educated guess B. Theory – successfully tested hypothesis C. Law – Theory with NO known exceptions

  28. Hypothesis Theory Law

  29. Control Vs. Experimental Groups • Control – Nothing happens to • Experimental – Change ONE variable Example: Plant growth Control Experimental

  30. 16a) 1.5 X 1011 m b) 150 Gm 32a) 0.10 nm b) 1.0 X 105 fm c) 1.0 X 1010 A d) 9.5 X 1025 A 42a) 1.00 X 109 cm3 b) 3.53 X 104 ft3 c) 6.10 X 107 in3

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