SI units
The international system of units (SI) is founded on the seven base quantities. It was created in order to establish an internationally agreed set of quantity measurement standards.
| Base quantity | Unit | Symbol |
| Mass | Kilogram | Kg |
| Length | Meter | M |
| Time | Second | S |
| Quantity of matter | Mole | Mol |
| Temperature | Kelvin | K |
| Electric current | Ampere | A |
SI prefixes
Each prefix can go before any SI unit.
| T | tera | x1012 |
| G | giga | x109 |
| M | mega | x106 |
| K | kilo | x103 |
| C | Centi | x10-2 |
| M | milli | x10-3 |
| µ | micro | x10-6 |
| n | nano | x10-9 |
| p | pico | x10-12 |
Limitations of physical measurements
Types of errors:
Measurement error: The margin of error when taking measurements.
Anomalies: A result which does not fit the trend/pattern.
Zero error: Error when taking measurements that don’t start from zero e.g. scales.
Random error: An uncontrollable error.
Systematic error: A continuous error that keeps occurring.
Accuracy- how close to the true value it is
Precision- values with very little spread about the mean values
Repeatability- can the experiment be repeated with the same method and equipment and still obtain the same value.
Reproducibility- can the investigation be repeated by another person using different equipment and get the same results.
Calculating uncertainties
Resolution- the smallest quantity that can be measured with the equipment.