Physic Tutorials

Fundamental And Derived Quantities With Examples

Measurement is a very important aspect of physics and other sciences. No fact in science is accepted, and no law is established unless it can be exactly measured and quantified. As physics is based on exact measurements, every such measurement requires two things: first, a number or quantity, and second, a unit. So, at the end of this write-up, you should be able to distinguish between fundamental and derived quantities and units.

Read: Scalar and Vector quantities

Fundamental quantity

Fundamental quantities are the basic quantities independent of others and cannot be defined in terms of other quantities or derived from them. They are basic quantities upon which most (though not all) quantities depend.

Fundamental units are the basic units upon which other units depend. They are the units of the fundamental quantities.

The three most important basic quantities in physics are length, mass, and time.

  • Length may be defined as the extent of space or distance extended
  • Mass is commonly defined as the quantity of matter or material substance.
  • Time is defined as the time in which events are distinguishable before or after.

Therefore, Length, Mass, and Time are the three fundamental quantities.

There are seven (7) basic fundamental quantities in physics, and they are given in the table below

QuantityUnitUnit abbreviation
Electric CurrentampereA
Amount of SubstancemoleMol.
Luminous IntensityCandellaCd

The units in the table are SI (Systeme International) units and are the principal system of units used in scientific work today.

Read: Questions on measurements

Derived Quantities

Derived quantities and units are those obtained by some simple combination of the fundamental quantities and units. They are thus dependent on the fundamental quantities and units.

Examples of Derived Quantities

Derived quantityDerivationDerived unit
Arealength x lengthm2
volumeLength x length x heightm3
accelerationChange in velocity/timems-2
forceMass x accelerationKgms-2 (Newton, N)
Energy or workForce x distanceKgm2s-2 or Nm (Joule, J)
powerWork/timeJs-1 (or watt, W)
momentumMass x velocityKgms-1; Ns
pressureForce/areaNm-2 (Pascal, Pa)
frequencyNumber of oscillations/times-1 (hertz, Hz)

Bolarinwa Olajire

A tutor with a demonstrated history of working in the education industry. Skilled in analytical skills. Strong education professional with a M. SC focused in condensed matter. You can follow me on Twitter by clicking on the icon below to ask questions.

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