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Unit 3

Unit 3. Physics and Physical measurement. Ranges of sizes, masses and times. Order of magnitude. We can express small and large numbers using exponential notation The number of atoms in 12g of carbon is approximately 600000000000000000000000. This can be written as 6 x 10 23.

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Unit 3

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  1. Unit 3 Physics and Physical measurement

  2. Ranges of sizes, masses and times

  3. Order of magnitude We can express small and large numbers using exponential notation The number of atoms in 12g of carbon is approximately 600000000000000000000000 This can be written as 6 x 1023

  4. Order of magnitude We can say to the nearest order of magnitude (nearest power of 10) that the number of atoms in 12g of carbon is 1024 (6 x 1023 is 1 x 1024 to one significant figure)

  5. Small numbers Similarly the length of a virus is 2.3 x 10-8 m. We can say to the nearest order of magnitude the length of a virus is 10-8 m.

  6. Ranges of sizes, masses and times You need to have an idea of the ranges of sizes, masses and times that occur in the universe.

  7. Size Can you think of 5 objects? Can you then list them in order of decreasing size (length) http://www.joemonster.org/gry/41805/Scale_of_the_Universe_2

  8. Size Which is the smallest on your list? What size is it to the nearest order of magnitude? http://www.joemonster.org/gry/41805/Scale_of_the_Universe_2

  9. Size The smallest objects that you need to consider are subatomic particles (protons and neutrons). These have a size (to the nearest order of magnitude) of 10-15 m.

  10. Size Which is the largest on your list? How large is it to the nearest order of magnitude?

  11. Size The largest object that you need to consider is the Universe. The Universe has a size (to the nearest order of magnitude) of 1025 m.

  12. Mass On your paper can you estimate the masses of the largest and smallest objects you have written?

  13. Mass The lightest particle you have to consider is the electron. What do you think the mass of the electron is? 10-30 kg! (0.000000000000000000000000000001 kg)

  14. Mass We have already decided that the Universe is the largest object. What do you think its mass is? 1050 kg (100000000000000000000000000000000000000000000000000 kg)

  15. Time Now think of 5 time intervals (For example, the time it takes to walk from Maths to Physics, the time it takes to walk from Physics to Maths etc.)

  16. Time The smallest time interval you need to know is the time it takes light to travel across a nucleus. Can you estimate it? 10-24 seconds

  17. Time What’s the longest time interval you thought of?

  18. Time The age of the universe. Any ideas?

  19. Time The age of the universe. 12 -14 billion years 1018 seconds

  20. Copy please! Size 10-15 m to 1025 m (subatomic particles to the extent of the visible universe) Mass 10-30 kg to 1050 kg (mass of electron to the mass of the Universe) Time 10-23 s to 1018 s (time for light to cross a nucleus to the age of the Universe)

  21. A common ratio – Learn this! Hydrogen atom≈ 10-10 m Proton ≈ 10-15 m Ratio of diameter of a hydrogen atom to its nucleus = 10-10/10-15 = 105

  22. Estimation You have to be able to make order of magnitude estimates.

  23. Estimation/Guess What’s the difference?

  24. Estimate the following: (to the nearest order of magnitude) • The mass of an apple

  25. Estimate the following: (to the nearest order of magnitude) • The mass of an apple • The number of times a human heart beats in a lifetime.

  26. Estimate the following: (to the nearest order of magnitude) • The mass of an apple • The number of times a human heart beats in a lifetime. • The speed a cockroach can run. A fast South American one!

  27. Estimate the following: (to the nearest order of magnitude) • The mass of an apple • The number of times a human heart beats in a lifetime. • The speed a cockroach can run. • The number of times the earth will fit into the sun (Rs = 6.96 x 108 m, Re = 6.35 x 106 m)

  28. Estimate the following: (to the nearest order of magnitude) • The mass of an apple • The number of times a human heart beats in a lifetime. • The speed a cockroach can run. • The number of times the earth will fit into the sun (Rs = 6.96 x 108, Re = 6.35 x 106)

  29. Estimate the following: (to the nearest order of magnitude) • The mass of an apple 10-1 kg • The number of times a human heart beats in a lifetime. • The speed a cockroach can run. • The number of times the earth will fit into the sun (Rs = 6.96 x 108, Re = 6.35 x 106)

  30. Estimate the following: (to the nearest order of magnitude) • The mass of an apple 10-1 kg • The number of times a human heart beats in a lifetime. 70x60x24x365x70=109 • The speed a cockroach can run. • The number of times the earth will fit into the sun (Rs = 6.96 x 108, Re = 6.35 x 106)

  31. Estimate the following: (to the nearest order of magnitude) • The mass of an apple 10-1 kg • The number of times a human heart beats in a lifetime. 70x60x24x365x70=109 • The speed a cockroach can run. 100 m/s • The number of times the earth will fit into the sun (Rs = 6.96 x 108, Re = 6.35 x 106)

  32. Estimate the following: (to the nearest order of magnitude) • The mass of an apple 10-1 kg • The number of times a human heart beats in a lifetime. 70x60x24x365x70=109 • The speed a cockroach can run. 100 m/s • The number of times the earth will fit into the sun (6.96 x 108)3/(6.35 x 106)3 = 106

  33. Estimate the following: (to the nearest order of magnitude) • The mass of an apple 10-1 kg • The number of times a human heart beats in a lifetime. 70x60x24x365x70=109 • The speed a cockroach can run. 100 m/s • The number of times the earth will fit into the sun (6.96 x 108)3/(6.35 x 106)3 = 106

  34. Let’s do some more estimating!

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