1. Physics and Physical Measurement
Topic 1.1 The Realm of Physics
Range of magnitudes of quantities in our universe

2. Range of Magnitudes This can be written as 6 x 1023
You will need to be able to state (express) quantities to the nearest order of magnitude
That is to say to the nearest 10x
The number of atoms in 12g of carbon is approximately
This can be written as 6 x 1023

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

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

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

6. Size
On your paper, write in order of decreasing size the names of 5 very small things.

7. Size
Which is the smallest? What size is it to the nearest order of magnitude?

8. Size
The smallest objects that you need to consider in IB physics are subatomic particles (protons and neutrons).
These have a size (to the nearest order of magnitude) of m.

9. Size
On your paper can you write in order of increasing size the names of 5 very large things.

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

11. Size
The largest object that you need to consider in IB physics 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 5 smallest objects you wrote down earlier.

13. Mass
What do you think the mass of the electron is?
10-30 kg!
( kg)

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

15. Time Now think of 5 small time intervals
For example, the time it takes sound to travel 1 metre is a small time interval.
Can you think of a smaller one?

16. Time Can you add order of magnitude estimates for your time intervals?
(For example, the time it takes sound to travel 1 metre is 10-3 seconds to the nearest order of magnitude)

17. Time
The smallest time interval you need to know is the time it takes light to travel across a nucleus.
Can you estimate it?
10-23 seconds

18. Time
What’s the longest time interval you can think of?
75 mins

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

20. Time
The age of the universe.
1018 seconds

21. 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 (electron to the Universe)
Time
10-23 s to 1018 s (time for light to cross a nucleus to the age of the Universe)

22. Estimation
For IB you have to be able to make order of magnitude estimates.
What’s the difference
between an estimate
and a guess?

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

24. 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.

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.
The speed a cockroach can run.

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.
The number of times the earth will fit into the sun (Rs = 6.96 x 108, Re = 6.35 x 106)

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, Re = 6.35 x 106)
The number lame jokes Mr. Fong will tell in his teaching career.

28. 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)
The number lame jokes Mr. Fong will tell in his teaching career.

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. 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)
The number lame jokes Mr. Fong will tell in his teaching career.

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. 100 m/s
The number of times the earth will fit into the sun (Rs = 6.96 x 108, Re = 6.35 x 106)
The number lame jokes Mr. Fong will tell in his teaching career.

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 (6.96 x 108)3/(6.35 x 106)3 = 106
The number lame jokes Mr. Fong will tell in his teaching career.

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
The number lame jokes Mr. Fong will tell in his teaching career.