Unit Conversion and Fermi Questions

1. Unit Conversionand Fermi Questions SPH3U

2. Unit Conversion: Learning Goals • The student will be able to use and convert between different numeric representations of quantitative data. (A1.12)

3. Unit Conversion: Learning Goals • The student will be able to use and convert between different numeric representations of quantitative data. (A1.12) • The student will also be able to use methods of unit conversion to make Fermi approximations of physical quantities.

4. Why all the fuss about units? Measurements of physical quantities must be expressed in terms of units that are defined by convention and related to some standard.

5. Why all the fuss about units? Measurements of physical quantities must be expressed in terms of units that are defined by convention and related to some standard.

6. Why all the fuss about units? Measurements of physical quantities must be expressed in terms of units that are defined by convention and related to some standard.

7. Why all the fuss about units? Measurements of physical quantities must be expressed in terms of units that are defined by convention and related to some standard.

8. Why all the fuss about units? Measurements of physical quantities must be expressed in terms of units that are defined by convention and related to some standard.

9. Why all the fuss about units? Measurements of physical quantities must be expressed in terms of units that are defined by convention and related to some standard. The measurement or calculation of a length may never be expressed as just 2.5: units must be given to indicate if the length is 2.5 km, 2.5 m, or 2.5 cm.

10. The SI System Physics uses SI (Système international) units, in which the base units are:

11. The SI System Physics uses SI (Système international) units, in which the base units are: • mass

12. The SI System Physics uses SI (Système international) units, in which the base units are: • mass kilogram (kg) Historically the mass of 1 litre of water, now defined as the mass of the International Prototype Kilogram, a chunk of platinum-iridium alloy stored in a vault in Paris.

13. The SI System Physics uses SI (Système international) units, in which the base units are: • mass kilogram (kg) • length

14. The SI System Physics uses SI (Système international) units, in which the base units are: • mass kilogram (kg) • length metre (m) Historically 1⁄10,000,000 of the distance from the Earth’s equator to the North Pole, now defined as the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.

15. The SI System Physics uses SI (Système international) units, in which the base units are: • mass kilogram (kg) • length metre (m) • time

16. The SI System Physics uses SI (Système international) units, in which the base units are: • mass kilogram (kg) • length metre (m) • time second (s) Historically 1⁄(24 × 60 × 60) of the day, now defined as the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.

17. The SI System Physics uses SI (Système international) units, in which the base units are: • mass kilogram (kg) • length metre (m) • time second (s) Minutes and hours are also acceptable units; use whichever time interval is appropriate to the situation being studied.

18. The SI System Physics uses SI (Système international) units, in which the base units are: • mass kilogram (kg) • length metre (m) • time second (s) • electric current

19. The SI System Physics uses SI (Système international) units, in which the base units are: • mass kilogram (kg) • length metre (m) • time second (s) • electric current ampere (A)

20. The SI System Physics uses SI (Système international) units, in which the base units are: • mass kilogram (kg) • length metre (m) • time second (s) • electric current ampere (A) • temperature

21. The SI System Physics uses SI (Système international) units, in which the base units are: • mass kilogram (kg) • length metre (m) • time second (s) • electric current ampere (A) • temperature kelvin (K)

22. The SI System Physics uses SI (Système international) units, in which the base units are: • mass kilogram (kg) • length metre (m) • time second (s) • electric current ampere (A) • temperature kelvin (K) However, since +1 degree K = +1 degree C (the scales just have different zero points), we will also be using Celsius.

23. Derived Units Other units may be derived from these base units.

24. Derived Units Other units may be derived from these base units. For example, acceleration may be expressed in units of m/s/s (metres per second per second) or m/s2;

25. Derived Units Other units may be derived from these base units. For example, acceleration may be expressed in units of m/s/s (metres per second per second) or m/s2; force may be expressed in units of kg m/s2, also known as Newtons (N);

26. Derived Units Other units may be derived from these base units. For example, acceleration may be expressed in units of m/s/s (metres per second per second) or m/s2; force may be expressed in units of kg m/s2, also known as Newtons (N); and energy may be expressed in units of kg m2/s2, also known as Joules (J).

27. Prefixes A metric prefix may be used to indicate a unit that is some power of ten larger or smaller than the SI unit.

28. Prefixes A metric prefix may be used to indicate a unit that is some power of ten larger or smaller than the SI unit. For example, 1 km =

29. Prefixes A metric prefix may be used to indicate a unit that is some power of ten larger or smaller than the SI unit. For example, 1 km = 1000 m or 1 × 103 m

30. Common Prefixes • 109

31. Common Prefixes • 109 Giga (G)

32. Common Prefixes • 109 Giga (G) • 106

33. Common Prefixes • 109 Giga (G) • 106 Mega (M)

34. Common Prefixes • 109 Giga (G) • 106 Mega (M) • 103

35. Common Prefixes • 109 Giga (G) • 106 Mega (M) • 103 kilo (k)

36. Common Prefixes • 109 Giga (G) • 106 Mega (M) • 103 kilo (k) • 10-2

37. Common Prefixes • 109 Giga (G) • 106 Mega (M) • 103 kilo (k) • 10-2 centi (c)

38. Common Prefixes • 109 Giga (G) • 106 Mega (M) • 103 kilo (k) • 10-2 centi (c) • 10-3

39. Common Prefixes • 109 Giga (G) • 106 Mega (M) • 103 kilo (k) • 10-2 centi (c) • 10-3 milli (m)

40. Common Prefixes • 109 Giga (G) • 106 Mega (M) • 103 kilo (k) • 10-2 centi (c) • 10-3 milli (m) • 10-6

41. Common Prefixes • 109 Giga (G) • 106 Mega (M) • 103 kilo (k) • 10-2 centi (c) • 10-3 milli (m) • 10-6 micro (m)

42. Common Prefixes • 109 Giga (G) • 106 Mega (M) • 103 kilo (k) • 10-2 centi (c) • 10-3 milli (m) • 10-6 micro (m) • 10-9

43. Common Prefixes • 109 Giga (G) • 106 Mega (M) • 103 kilo (k) • 10-2 centi (c) • 10-3 milli (m) • 10-6 micro (m) • 10-9 nano (n)

44. All the Prefixes

45. Common Prefixes For example, • 2 ms =

46. Common Prefixes For example, • 2 ms = 2 × 10-6 s Know how to enter this number in your calculator (usually as either 2 EXP -6 or 2 EE -6 or 2 10x -6).

47. Common Prefixes For example, • 2 ms = 2 × 10-6 s • 2 ns =

48. Common Prefixes For example, • 2 ms = 2 × 10-6 s • 2 ns = 2 × 10-9 s

49. Common Prefixes For example, • 2 ms = 2 × 10-6 s • 2 ns = 2 × 10-9 s • 20 ns =

50. Common Prefixes For example, • 2 ms = 2 × 10-6 s • 2 ns = 2 × 10-9 s • 20 ns = 20 × 10-9 s