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ICSE-IX-Physics

01: Measurements and Experimentation

with Solutions -

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    Section : A
  • Qstn #1
    What is meant by measurement?
    Ans : Measurement is the process of comparing a given physical quantity with a known standard quantity of the same nature.
  • Qstn #2
    What do you understand by the term unit?
    Ans : Unit is the quantity of a constant magnitude which is used to measure the magnitudes of other quantities of the same nature.
  • Qstn #3
    What are the three requirements for selecting a unit of a physical quantity?
    Ans : The three requirements for selecting a unit of a physical quantity are:

    1. It should be possible to define the unit without ambiguity.

    2. The unit should be reproducible.

    3. The value of units should not change with space and time.

  • Qstn #4
    Name the three fundamental quantities.
    Ans : The three fundamental quantities are:

    1. Length

    2. Mass

    3. Time

  • Qstn #5
    Name the three systems of unit and state the various fundamental units in them.
    Ans : The three systems of unit and the corresponding fundamental units are:

    1. CGS system (French System): unit of length is centimeter (cm), unit of mass is Gram(g), unit of time is Second(s)

    2. F.P.S system (British system): unit of length is Foot(ft), unit of mass is Pound(Ib), unit of ime is Second(s)

    3. M.K.S system (Metric system): unit of length is Metre(m), unit of mass is Kilogramme(kg), unit of time is Second(s)

  • Qstn #6
    Define a fundamental unit.
    Ans : A fundamental (or basic) unit is that which is independent of any other unit or which can neither be changed nor can be related to any other fundamental unit.
  • Qstn #7
    What are the fundamental units in S.I. system? Name them along with their symbols.
    Ans :
    Quantity Unit Symbol
    Length metre m
    Mass kilogram Kg
    Time second S
    Temperature kelvin K
    Luminous intensity candela cd
    Electric current ampere A
    Amount of substance mole mol
    Angle radian rd
    Solid angle steradian St-rd
  • Qstn #8
    Explain the meaning of derived unit with the help of one example.
    Ans : The units of quantities other than those measured in fundamental units can be obtained in terms of the fundamental units, and thus the units so obtained are called derived units.
    Example:
    Speed = Distance/time
    Hence, the unit of speed = fundamental unit of distance/fundamental unit of time
    Or, the unit of speed = metre/second or ms-1
    As the unit of speed is derived from the fundamental units of distance and time, it is a derived unit.
  • Qstn #9
    Define standard metre.
    Ans : A metre was originally defined in 1889 as the distance between two marks drawn on a platinum-iridium (an alloy with 90% platinum and 10% iridium) rod kept at 0° C in the International Bureau of Weights and Measures at serves near Paris.
  • Qstn #10
    Name two units of length which are bigger than a metre. How are they related to the metre?
    Ans : Astronomical unit (A.U.) and kilometer (km) are units of length which are bigger than a metre.
    1 km = 1000 m
    1 A.U. = 1.496 x 1011 m
  • Qstn #11
    Write the name of two units of length smaller than a metre. How are they related to the metre?
    Ans : The two units of length smaller than a metre are:

    • Angstrom (Ã…)

    • Fermi
      (d)


    Relation between metre (m) and Angstrom (Ã…) is:
    1 Angstrom (Ã…) = 10-10 metre
    Relation between metre (m) and Fermi is:
    1 fermi
    (d) = 10-15 m
  • Qstn #12
    How is nanometer related to Angstrom?
    Ans : Relation between nanometer (nm) and Angstrom (A):
    1 nanometer = 10Ã…
  • Qstn #13
    Name the three convenient units used to measure length ranging from very short to very long value. How are they related to the S.I. unit?
    Ans : The 3 convenient units used to measure length ranging from very short to very long value are:

    • Centimeter (cm)

    • Metre (m)

    • Kilometer (km)


    Relation between meter (m) and the units are:
    1 m = 100cm
    1 km = 1000m
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