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# Measurements units

## on Aug 25, 2010

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## Measurements unitsPresentation Transcript

• Measurements and Units Quantities and Units
• Quantities and Units
• Form sentences with these quantities:
3m 2 65km/h 1.76m
• Physical Quantities are measurable and have physical (feel, see…) meaning.
Quantities and Units Numerical Value Unit 4.5 m
• Quantities and Units
• There are many units for each quantities
• Example - Length:
• metres, centimetres, kilometres, feet, inches, miles, nautical miles, light year
• Only one of the many is an SI unit
• Quantities and Units kg Kilogram Mass K Kelvin Temperature s Second Time m Metre Length Symbol SI Unit Quantity
• Quantities and Units
• SI units for some other quantities.
• When solving questions involving quantities. These quantities must have the same unit.
kg/m 3 density m 3 volume m 2 area m/s speed Unit Quantites
• Quantities and Units
• Example
• 400 cm 3 of water is added to 1 litre of water. How much water is there?
• Incorrect: 400 + 1 = 401cm 3
• Correct: 1 litre = 1000cm 3
• 400 + 1000 = 1400 cm 3
• Quantities and Units
• Very small numbers may have prefixes to make writing them easier.
• Example
• 2 000 000 000 Byte = 2 GByte
• 0.000045 m = 45  m
• Quantities and Units One billionth One millionth One thousandth One hundredth One tenth One thousand One million One billion Value n nano µ Micro m Milli c Centi d Deci K Kilo M Mega G Giga Symbol Prefix
• Conclusion
• Numerical values and units give quantities meaning.
• Only quantities that have the same units can be added or subtracted.
• Prefixes may be added to very small quantities.