Measurements units

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Measurements units

  1. 1. Measurements and Units Quantities and Units
  2. 2. Quantities and Units <ul><li>Form sentences with these quantities: </li></ul>3m 2 65km/h 1.76m
  3. 3. <ul><li>Physical Quantities are measurable and have physical (feel, see…) meaning. </li></ul>Quantities and Units Numerical Value Unit 4.5 m
  4. 4. Quantities and Units <ul><li>There are many units for each quantities </li></ul><ul><li>Example - Length: </li></ul><ul><li>metres, centimetres, kilometres, feet, inches, miles, nautical miles, light year </li></ul><ul><li>Only one of the many is an SI unit </li></ul>
  5. 5. Quantities and Units kg Kilogram Mass K Kelvin Temperature s Second Time m Metre Length Symbol SI Unit Quantity
  6. 6. Quantities and Units <ul><li>SI units for some other quantities. </li></ul><ul><li>When solving questions involving quantities. These quantities must have the same unit. </li></ul>kg/m 3 density m 3 volume m 2 area m/s speed Unit Quantites
  7. 7. Quantities and Units <ul><li>Example </li></ul><ul><li>400 cm 3 of water is added to 1 litre of water. How much water is there? </li></ul><ul><li>Incorrect: 400 + 1 = 401cm 3 </li></ul><ul><li>Correct: 1 litre = 1000cm 3 </li></ul><ul><li>400 + 1000 = 1400 cm 3 </li></ul>
  8. 8. Quantities and Units <ul><li>Very small numbers may have prefixes to make writing them easier. </li></ul><ul><li>Example </li></ul><ul><li>2 000 000 000 Byte = 2 GByte </li></ul><ul><li>0.000045 m = 45  m </li></ul>
  9. 9. 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
  10. 10. Conclusion <ul><li>Numerical values and units give quantities meaning. </li></ul><ul><li>Only quantities that have the same units can be added or subtracted. </li></ul><ul><li>Prefixes may be added to very small quantities. </li></ul>

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