Physical Quantities & Necessary Characteristics

What are Physical Quantities?

Physical Quantities are the quantities that are measurable i.e. length, mass, time, temperature, etc.

Other Definitions of Physical Quantity

  • Physical quantity is a characteristic or property of an object that can be measured or calculated from other measurements
  • A physical quantity is a property of a material or system that can be quantified by measurement.

What are two necessary characteristics of Physical Quantity?

Each physical quantity possesses at least the following two characteristics:

  1. Numerical Magnitude
  2. Measuring Unit (in which that physical quantity is measured)

For example, if the length of a student is 104 cm then 104 is its numerical magnitude and
the centimeter is the unit of measurement.

Similarly, when a shopkeeper says that each packet of salt contains 500 gm salt, he is actually telling the numerical magnitude i.e. 500 and the unit of measurement i.e. gm.

List down the two types of physical quantities

Physical quantities are divided into 2 types:-

  • Base (Fundamental) Quantities
  • Derived Quantities

What do you mean by Base Quantities?

The physical quantities which form the foundation for other physical quantities are called Base Quantities. Base quantities includes length, mass, time, electric current, temperature, the intensity of light and the amount of a substance.

Other Definitions of Base Quantities

  • Base quantities are the quantities on the basis of which other quantities are expressed.
  • Base quantities are physical quantities that cannot be defined in terms of other quantities

Tabulate the Base Quantities with their symbols.

Quantity NameSymbol
Lengthl
Massm
Timet
Electric CurrentI
Intensity of LightL
TemperatureT
Amount of a Substancen
Base Quantities

What are Derived Quantities?

Those physical quantities which are expressed in terms of base quantities are called the derived quantities. The derived quantities include area, volume, speed, force, work, energy, power, electric charge, electric potential, etc.

Other Definitions of Derived Quantities

  • A derived quantity is a quantity in a system of quantities that is defined in terms of only the base quantities of that system.
  • Derived quantities are physical quantities derived from combinations of base quantities through multiplication

Tabulate the Derived Quantities with their symbols.

Quantity NameSymbol
Speedv
Accelerationa
VolumeV
ForceF
PressureP
Densityp
ChargeQ
Derived Quantities

How can you differentiate between Base Quantities and Derived Quantities?

TitleBase QuantitiesDerived Quantities
FoundationBase Quantities form the foundation for derived quantities Derived Quantities are founded on the basis of Base Quantities
DefiningBase Quantities cannot be defined in terms of Derived QuantitiesDerived Quantities can be defined in terms of Base Quantities
CombinationBase Quantities are not the combination of two or more physical quantitiesDerived Quantities are the combination of two or more physical quantities
ExamplesBase Quantities are Length, Mass, Time, Electric Current, Intensity of Light, Temperature and Amount of a SubstanceDerived Quantities are Speed, Acceleration, Volum, Force, Pressure, Density, Charge, etc
Base Quantities vs Derived Quantities

Quiz

  1. Physical Quantities include
    1. all measurable quantities
    2. all unmeasurable quantities
    3. all quantities
    4. all of the above
  2. Physical Quantities have the following characteristic(s):
    1. Numerical Magnitude
    2. Measuring Unit
    3. Both of the above
    4. None of the above
  3. Length is the
    1. Base Quantity
    2. Derived Quantity
    3. Both of the above
    4. None of the above
  4. The intensity of the light is the
    1. Base Quantity
    2. Derived Quantity
    3. Both of the above
    4. None of the above
  5. Volume is the
    1. Base Quantity
    2. Derived Quantity
    3. Both of the above
    4. None of the above
  6. Density is the
    1. Physical Quantity
    2. Derived Quantity
    3. Both of the above
    4. None of the above
  7. Base Quantities form the foundation for
    1. Derived Quantities
    2. Other Physical Quantities
    3. Both of the above
    4. None of the above
  8. Which quantities are the combination of two or more physical quantities
    1. Base Quantities
    2. Derived Quantities
    3. Both of the above
    4. None of the above
  9. Base Quantities can be defined in terms of
    1. Derived Quantities
    2. Other Physical Quantities
    3. Both of the above
    4. None of the above
  10. Which of the following can be a numerical magnitude
    1. 104 cm
    2. cm
    3. 104
    4. None of the above

Quiz with Answers

[ays_quiz id=”4″]

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