Introduction to Units and Measurement
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Questions and Answers

What is the basic standard for measurement called?

unit

What are the fundamental or base quantities' units known as?

fundamental or base units

Which of the following is NOT one of the fundamental base units?

  • Metre
  • Second
  • Pound (correct)
  • Kilogram
  • Match the following systems of units with their base units for length, mass, and time:

    <p>CGS = Centimetre, Gram, Second FPS = Foot, Pound, Second MKS = Metre, Kilogram, Second</p> Signup and view all the answers

    What is the SI system of units?

    <p>Système Internationale d’Unites</p> Signup and view all the answers

    The SI units use a decimal system.

    <p>True</p> Signup and view all the answers

    What are the additional units in SI defined for plane angle and solid angle?

    <p>Radian and Steradian</p> Signup and view all the answers

    Define the base quantity for length in the SI system.

    <p>Metre</p> Signup and view all the answers

    Study Notes

    Introduction to Units and Measurement

    • Measurement involves comparing a physical quantity with a standard reference called a unit.
    • The result of a measurement is expressed as a numerical value with a corresponding unit.
    • There are fundamental (base) units for basic quantities like length, mass, and time.
    • Other physical quantities can be expressed as combinations of base units, leading to derived units.
    • A system of units encompasses both base and derived units.

    The International System of Units (SI)

    • SI is the internationally accepted system of units for measurement.
    • It uses a standardized scheme of symbols, units, and abbreviations.
    • The International System of Units (SI) uses a decimal system for conversions, making them simple and convenient.

    Base Units in Different Systems

    • The CGS System: Uses centimeter (cm), gram (g), and second (s) for length, mass, and time respectively.
    • The FPS (British) System: Uses foot (ft), pound (lb), and second (s) for length, mass, and time respectively.
    • The MKS System: Uses meter (m), kilogram (kg), and second (s) for length, mass, and time respectively.

    SI Base Units and Definitions

    • Length: The meter (m) is defined as the distance traveled by light in a vacuum during a time interval of 1/299,792,458 of a second.
    • Mass: The kilogram (kg) is defined as the mass of the international prototype of the kilogram, a platinum-iridium alloy cylinder kept at the International Bureau of Weights and Measures (BIPM) in France.
    • Time: The second (s) is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.
    • Electric Current: The ampere (A) is defined as the constant current that, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 × 10−7 newton per meter of length.
    • Temperature: The kelvin (K) is defined as 1/273.16 of the thermodynamic temperature of the triple point of water.
    • Amount of Substance: The mole (mol) is defined as the amount of substance that contains as many elementary entities as there are atoms in 0.012 kilogram of carbon-12.
    • Luminous Intensity: The candela (cd) is defined as the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

    SI Supplementary Units

    • Plane Angle (dθ): Unit is radian (rad). Defined as the ratio of arc length (ds) to the radius (r).
    • Solid Angle (dΩ): Unit is steradian (sr). Defined as the ratio of the intercepted area (dA) of a spherical surface to the square of its radius (r).

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    Units and Measurement PDF

    Description

    Explore the fundamental concepts of units and measurement, including the importance of base and derived units. This quiz covers the International System of Units (SI) and different measurement systems, highlighting their significance in expressing physical quantities accurately.

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