Measurements-also.pptx jsjsjkajnsbsjajjajwjn

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1. Measurement Celestie C. Apita MT-II, ESNCHS

2. Objectives: Differentiate random errors from systematic e rrors ; Differentiate accuracy from precision; Solve measurement problems involving conversion of units, expression of measurements in scientific notation; and Estimate errors from multiple measurements of a physical quantity using variance.

3. Let us try this. Group 1 – hand Group 2 – foot Group 3 - ruler Group 4 - meterstick Using the assigned material, determine the length of your classroom. Decide with your groupmates on a value to report to class after 5 minutes.

4. Guide Questions: Think about these. Which measuring tool did you use to measure the identified lengths? What unit of measure/ dimensions did you use? How do you suppose the choice of measuring tool affects the value that will be determined? How about the unit of measure? What did you do to ensure that you get an accurate and precise measurement value/s? Which group’s measurement value is perfect? Explain.

5. True or False: “ Errors accompany ALL measurements.”

6. Types of Errors Random Error - caused by things that are unknown and uncontrollable on the measurer’s part thus, commonly goes undetected or accounted for in measurements. Example : Measurer’s interpretation/ perception of where the measurement device’s pointer points Systematic Error - caused by faulty measuring devices. Example : device’s pointer not initially set to zero

7. Accuracy vs. Precision A B C

8. Accuracy – how close a single measurement value is to the target/ expected value. Precision – how close multiple measurements are to each other.

9. Let’s look at this.

10. Conversion of Units

11. SI Fundamental Units Quantity Unit Symbol Length meter m Mass kilogram kg Time second s Temperature kelvin K Electric Current ampere A Luminous Intensity candela cd Amount of Substance mole mol

12. Let us hear your jokes! 

13. Conversion of Units Dimensional Analysis Method (DAM) - used to eliminate “undesired” with “desired” units of measure or dimensions.

14. Exercises on Conversion of Units Convert the following as indicated 45.3 kg = ______ g 330 mL = _____ L 5’2” = ______ cm 48.0 h = ______ s 40.0 kph = _____ m/s 10.0 m 3 = _____ cm 3

15. Scientific Notation A way of expressing very small or very large numbers Decimal point is moved resulting one non-zero digit to its left Example: Parts: coefficient, base, and exponent  

16. Exercises Express the following in scientific notation. c = 299792458.0 m / s m n = 0.000 000 000 000 000 000 000 000 0016749272111842 kg N A = 602 214 179 130 200 000 000 000 molecules/mol 8 990 000 000.0 Nm 2 /C 2  

17. Rules for Significant Figures Non-zero digits are always significant Any zeros between two significant digits are significant A final zero or trailing zeros in the decimal portion ONLY are significant.

18. Rules for Significant Figures Multiplication or division: The result should have the same number of SFs as the factor with the fewest SFs. Addition or Subtraction: The result should have the same decimal digits as the number with the least decimal digits.

19. Exercises (a) 8.4 h (b) 173.6 m (c) 407.00 g (d) 4.68 m (e) 8.1165 kg (f) 0.054 km (g) 0.00343 L (h) 93.040 mg ( i ) 30.030300 g (j) 40.00 km (k) 3.600 ml (l) 70.002 cm 3 Determine the number of SFs.

20. Exercises (a) 57.3628 g (b) 6.31874 kg (c) 44.422 km (d) 60.001 cm (e) 0.0023596 m Round off each of the following correctly up to 3 SFs.

21. TRY THESE! The following conversions occur frequently in physics and are very useful. Use 1 mi = 5280 ft and 1 h = 3600 s to convert to 60 mph to units of ft/s. The acceleration of a freely falling object is 32 ft/s 2 . Use 1 ft = 30.48 cm to express this acceleration in units of m/s 2 . The density of water is 1.0 g/cm 3 . Convert this density to units of kg/m 3 .

22. Thank you!