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PPMF101 – Lecture 1

PPMF101 – Lecture 1. Measurement. Base quantity A quantity which is not a combination of other physical quantities. Must be defined in terms of a standard. Length, mass, time, temperature, electric current, amount of substance and luminous intensity. Derived quantity

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PPMF101 – Lecture 1

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  1. PPMF101 – Lecture 1 Measurement

  2. Base quantity A quantity which is not a combination of other physical quantities. Must be defined in terms of a standard. Length, mass, time, temperature, electric current, amount of substance and luminous intensity Derived quantity A quantity which is a combination of two or more physical quantities. Eg. Area, volume, velocity, acceleration, density, work, energy and pressure. Basic quantity & Derived quantity

  3. 1 meter • The meter is the length of the path traveled by light in vacuum during a time interval of 1/299,792,458 of a second. • 1 meter is defined in terms of the distance traveled by light in vacuum. Velocity of light in vacuum is important in this definition.

  4. 1 kilogram • A particular platinum-iridium cylinder kept at the International Bureau of Weights and Measures near Paris. • 1 kilogram is defined by the mass of a particular platinum-iridium cylinder.

  5. 1 second • One second is defined as the time required for 9,192,631,770 periods of radiation emitted by cesium atoms. • 1 second is defined in terms of periods of radiation of cesium atom.

  6. Importance of unit conversion • Scientific purposes • Trades and commerce • Daily transaction

  7. Wrong conversion can lead to disaster • NASA Mars Climate Orbiter • "The 'root cause'of the loss of the spacecraft was the failed translation of English units into metric units in a segment of ground-based, navigation-related mission software, as NASA has previously announced," said Arthur Stephenson, chairman of the Mars Climate Orbiter Mission Failure Investigation Board.

  8. Wrong conversion can lead to disaster • September 30, 1999 • NASA lost a 125 million Mars orbiterbecause a Lockheed Martin engineering team used English units of measurement while the agency’s team used the more conventional metric system for a key spacecraft operation – CNN.

  9. Wrong conversion can almost lead to disaster • The Gimli Glideris the nickname of the Air Canada aircraft that was involved in a notable aviation incident. • On 23 July 1983, Air Canada Flight 143, a Boeing 767-200jet, ran out of fuel at 26,000 feet (7,920 m) altitude, about halfway through its flight from Montreal to Edmonton via Ottawa.

  10. The crew was able to glide the aircraft safely to an emergency landing at Gimli Industrial Park Airport, a former Canadian Air Force base at Gimli, Manitoba. • The incident was partly due to miscalculation in fuel reloading using metric system in place of the British system.

  11. Effective technique of Unit Conversion 1. Write the unit in traditional form and not the index form. eg. • Remember or look up the conversion factor. • Multiply the initial quantity with the proper conversion factor so that only the required units are left, the others cancelled off.

  12. Conversion factor to remember • 1 km = 1000 m • 1 m = 100 cm • 1 cm = 10 mm • 1 kg = 1000 g • 1 h = 60 min • 1 min = 60 s • 1 h = 3600 s • Remember the values for the prefixes. • The rest – look up the conversion table

  13. Unit Conversion • Convert • (a) 110 km/h to m/s • (b) 340 m/s to km/h • (c) 300 m2 to cm2 • (d) 20 m3 to cm3 • (e) 1000 kg/m3 • (f) 15 nm to m • (g) 25 A to A • (h) 12 MW to kW

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