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PHYSICS

Physics is the science that studies the nature of matter, energy and their relationships. PHYSICS. V. HASSELL. state the 5 base quantities and their SI unit. Metric System. SI unit of time second based on atomic standard radiation emitted by cesium 133. Metric System. SI unit of length

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PHYSICS

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  1. Physics is the science that studies the nature of matter, energy and their relationships. PHYSICS V. HASSELL

  2. state the 5 base quantities and their SI unit

  3. Metric System • SI unit of time • second • based on atomic standard • radiation emitted by cesium 133

  4. Metric System • SI unit of length • meter • wavelength of light emitted by krypton-86 • distance light travels in 1/2999 792 458 second

  5. Metric System • SI unit of mass • kilogram • the quantity of matter an object contains • mass of a platinum-iridium metal cylinder kept near Paris

  6. Standard Units • Kilo • Hecto • Deka • gram- meter- liter • deci • centi • milli

  7. Prefixes- fractions • deci d 1/10 or 10 -1 • centi c 1/100 or 10 -2 • milli m 1/1000 or 10 -3 • micro u 10 -6 • nano n 10 -9 • pico p 10 -12

  8. Prefixes- multiples • Deka da 10 1 • Hecto h 10 2 • Kilo k 10 3 • Mega M 10 6 • Giga G 10 9

  9. Fundamental quantities & units Derived quantities • mass- kg • length- meter • time- second • are combinations of fundamental quantities • density= mass/volume

  10. Significant Digits • Nonzero digits are always significant • All final zeros after the decimal point are significant • Significant digits are all the digits of a measurement that are certain plus one estimated digit. • Your answers cannot be more precise than the least precise quantity. • The sum or difference of two values is as precise as the least precise value.

  11. Zeros between two other significant digits are always significant • Zeros used solely for spacing the decimal point are not significant • In scientific notation all digits before the 10 are significant • 2.510 X 10 8 has ______ significant digits

  12. Significant Digits- X or / • The result of any mathematical operation with measurements can never be more precise than the least precise measurement. • Note the factor with the least number of significant digits. • Round the product or quotient to this number of digits.

  13. Scientific Notation • M X 10n • only 1 non-zero digit on the left of the decimal • the exponent gets larger as the number gets smaller

  14. 850 meters = ___________mm • smaller unit - the # gets larger • larger unit - the # gets smaller • number of places- deci, centi, milli • move 3 times- larger number • *smallest units will have largest numbers

  15. Conversion • 850 meters = ___________mm • 850,000 mm • or 8.5 X 10 5 mm

  16. OR Conversion • 850 meters = ___________mm • 1 meter = 1 X 1000 mm • 850 meters 1 X 1000 mm = 1 meter • 850,000 mm • or 8.5 X 10 5 mm

  17. OR Conversion • 850 meters = ___________mm • 1 meter = 1 X 10 3 mm • 850 meters 1 X 10 3 mm = 1 meter • 850 X 10 3 = 8.5 X 10 5 mm

  18. Add & Subtract exponents • the exponents must be the same • Add the numbers in front of the 10

  19. Add & Subtract exponents • 2.1 X 10 3 + 3.2 X 10 3 = • 2.1+ 3.2= 5.3 • 5.3 X 10 3

  20. Add & Subtract exponents • 3.2 X 10 3 - 2.1 X 10 3 = • 3.2-2.1 = 1.1 • 1.1 X 10 3

  21. Add & Subtract w/different exponents • Exponents must be the same number (doesn’t matter which one) • Change one of them to match the other (or in between) • Continue to add or subtract # before 10

  22. Add & Subtract different exponents • 5.5 X 10 -2 + 2.2 X 10 -3 = • 55 X 10 -3 + 2.2 X 10 -3 = • 57.2 X 10 -3= • 5.7 X 10-2

  23. Subtract • 5.5 X 10 -2 - 2.2 X 10 -3 = • 55 X 10 -3 - 2.2 X 10 -3 = • 52.8 X 10 -3 = • 5.28 X 10 -2 • 5.3 X 10 -2

  24. Multiply & Divide • Multiply or divide the # before 10 as indicated • add exponents in multiplication subtract exponents in division • check units. (May be m2 or m/sec)

  25. Muliply • 5.0 X 10 -2m X 3.0 X 10 -3m = • 15.0 X 10 -2 + -3 m2= • 15.0 X 10 -5 = • 1.5 X 10 -4 m2

  26. Divide • 6.6 X 10 -2m / 3.3 X 10 -5s = • 2.0 X 10 -2 - (-5) m/s= • 10 -2+ 5= 10 3 • 2.0 X 10 3m/s=

  27. 2.0 X 10 2m X 3.3 X 10 -5kg 6 X 10 -5s = • =6.6 X 102 + (-5)= -3 mkg= 6 X 10 -5s • 1.1 X 10 -3 -(-5)= -3+5=2 • 1.1 X 10 2 mkg/s

  28. All measurements are subject of uncertainties

  29. All instruments are subject to external influences. • Uncertainties in measurement cannot be avoided.

  30. Inaccuracies can be due to • human error in reading (precision) • accuracy of the devise

  31. Parallax • The apparent shift in the position of an object when it is viewed from various angles

  32. ==What is error?== • Error is the difference between the actual value of a quantity and the value obtained in measurement. • Systematic errors are errors which tend to shift all measurements in asystematic way so their mean value is displaced. Systematic errors can be compensated if the errors are known.

  33. Sources of Systematic Error • zero error, which cause by an incorrect position of the zero point • an incorrect calibration of the measuring instrument. • consistently improper use of equipment.

  34. Precision • The precision of a measurement describes how exactly it was measured • the ability of an instrument in measuring a quantity in a consistent manner with only a small relative deviation between readings

  35. What is meant by sensitivity of a measuring instrument?== • The precision of an instrument is limited by the smallest division on the measurement scale • Measuring instruments that have smaller scale parts are more sensitive. • Sensitive instruments need not necessarily be accurate.

  36. Micrometer Screw Gauge • Turn the thimble until the object is gripped gently between the anvil and spindle. • Turn the ratchet knob until a "click" sound is heard. This is to prevent exerting too much pressure on the object measured. • Take the reading.

  37. Micrometer Screw Gauge • Reading of main scale = 5.5mmReading of thimble scale = 0.27mmActual Reading = 5.5mm + 0.27mm = 5.77mm

  38. Accuracy • Accuracy of a measurement describes how well the result agrees with a standard value • The accuracy of a measurement is the approximation of the measurement to the actual value for a certain quantity

  39. Steps to reduce Systematic Error • Conducting the experiment with care. • Repeating the experiment by using different instruments.

  40. Random Error • Random errors arise from unknown and unpredictable variations in condition. • It changes from one measurement to the next. • Random error can cause by:lack of sensitivity of the instrument: the instrument fail to respond to the small change. • natural errors such as changes in temperature or wind, while the experiment is in progress. • wrong technique of measurement.

  41. How to avoid random error • Taking repeat readings • Find the average value of the reading.

  42. Zero Error • A zero error arises when the measuring instrument does not start from exactly zero. • Zero errors are consistently present in every reading of a measurement. • The zero error can be positive or negative.

  43. How to measure the precision of a measurement?== • The precision of a reading can be indicated by its relative deviation.The relative deviation is the percentage of mean deviation for a set of measurements and it is defined by the following formula:

  44. Review • Accuracy is determined by the preciseness of the measurement • To check the accuracy of an instrument you measure a standard devise to determine the deviation.

  45. accuracy • The accuracy of an instrument is usually off the same direction in all measurements. • Ex. • A scale which indicates a measurement over 0 with nothing being balanced will probably show a higher than accurate amount for all measurements.

  46. Murphy’s Law • Any error that can creep in, it will. It will be in the direction that will do most damage to the calculation.

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