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1.1 UNITS1.1 UNITS

1.1 UNITS

- 1.1.1 Symbols
- 1.1.2 Scientific notation
- 1.1.3 Unit prefixes
- 1.1.4 Logs
- 1.1.5 Accuracy
- 1.1.6 SI Units
- 1.1.7 Unit analysis

Scientific Notation

In order to make the number easier to use we commonly express it in scientific notation e.g: 2.304 106 kg.

- The 2.304 MUST be between 1 and 10. To express this number as 0.2304 107 or 23.04 105 is mathematically the same but should NOT be used because it is incorrect use of the notation.
- The number raised to a power must be 10, e.g. 86 or 76 should NOT appear in this notation.
- The power must be a positive or negative integer, e.g. numbers such as: 104.5 or 106.3 should NOT appear (but negative powers such as 10-4 may be used)

1.1 UNITS

- 1.1.1 Symbols
- 1.1.2 Scientific notation
- 1.1.3 Unit prefixes
- 1.1.4 Logs
- 1.1.5 Accuracy
- 1.1.6 SI Units
- 1.1.7 Unit analysis

Metric Prefixes

The alternative way of making the number easier to use is to change the units. For all metric units the prefixes are:

- G Giga 109
- M Mega 106
- k Kilo 103
- m milli 10-3
- micro 10-6
- n nano 10-9
- p pico 10-12
- Thus 2304000 kg = 2304 Mg

1.1 UNITS

- 1.1.1 Symbols
- 1.1.2 Scientific notation
- 1.1.3 Unit prefixes
- 1.1.4 Logs
- 1.1.5 Accuracy
- 1.1.6 SI Units
- 1.1.7 Unit analysis

Accuracy

- Depending on the accuracy known or required the number 2.304 106 might be expressed as: 2.3 106 kg or even 2 106 kg
- This may be correct but numbers should NEVER be rounded in this way until the end of a calculation.

- 1.1.1 Symbols
- 1.1.2 Scientific notation
- 1.1.3 Unit prefixes
- 1.1.4 Logs
- 1.1.5 Accuracy
- 1.1.6 SI Units
- 1.1.7 Unit analysis

Units

- MKS SI (Metre kilogramme second Systéme International) units in which masses are measured in kg and lengths in m.
- cgs (centimetre gramme second)
- Imperial/American (pounds weight and feet etc.)
- MKS units should always be used where possible.

In the metric system:

- 1 ml (millilitre) of water (= 1 cubic centimetre) weighs 1 g (gramme)
- 1 l (litre) of water weighs 1 kg (kilogramme)
- 1000 litres of water (= 1 cubic metre) weigh 1000kg (= 1 Tonne)
- Thus in MKS units the density of water is 1000 kg/m3

- 1.1.1 Symbols
- 1.1.2 Scientific notation
- 1.1.3 Unit prefixes
- 1.1.4 Logs
- 1.1.5 Accuracy
- 1.1.6 SI Units
- 1.1.7 Unit analysis

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