1.1 UNITS

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# 1.1 UNITS - PowerPoint PPT Presentation

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  10 6 kg.

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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

### Get your powers of 10 right!

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 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
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 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