8.2 Prefixes used with SI units
Now that you have met powers of ten, we can introduce the complete range of prefixes used with SI units. These are given in Table 8.1.
So, for example, 1 Ms = s. This is about 11.5 days.
| Prefix | Symbol | Multiplying factor |
|---|---|---|
| exa | E | 1018 = 1000 000 000 000 000 000 |
| peta | P | 1015 = 1000 000 000 000 000 |
| tera | T | 1012 = 1000 000 000 000 |
| giga | G | 109 = 1000 000 000 |
| mega | M | 106 = 1000 000 |
| kilo | k | 103 = 1000 (Note that it is ‘k’ and not ‘K’.) |
| - | - | 100 = 1 |
| deci | d | 10-1 = 0.1 |
| centi | c | 10-2 = 0.01 |
| milli | m | 10-3 = 0.001 |
| micro | μ | 10-6 = 0.000 001 |
| nano | n | 10-9 = 0.000 000 001 |
| pico | p | 10-12 = 0.000 000 000 001 |
| femto | f | 10-15 = 0.000 000 000 000 001 |
| atto | a | 10-18 = 0.000 000 000 000 000 001 |
Footnotes
The order of the top six prefixes (in ascending order) can be remembered with the phrase ‘king Midas’s Golden Touch Poisoned Everything’.Question 8.3
Express each of the following in metres, giving your answers in scientific notation. Example: km = m.
- a.6.1 Tm
6.1 Tm = 6.1 1012 m
- b.3.5 nm
3.5 nm = 3.5 10-9 m
- c.1.7 μm
1.7 μm = 1.7 10-6 m