# Primary quantity - Fluid Mechanics

Q.  Which of the following is not a primary quantity?
- Published on 04 Aug 15

a. Mass (M)
b. Temperature (θ)
c. Time (T)
d. None of the above

#### Discussion

• Pankaj   -Posted on 05 Oct 15
Dimensional analysis is a mathematical technique which deals with the dimensions of physical quantities in the phenomenon. In dimensional analysis, it is assumed that the phenomenon can be expressed by a dimensionally homogeneous equation with certain variables.

Some problems in fluid mechanics are difficult to solve due to their complexity. The solutions of these problems which are very complex in nature can considerably be simplified by using dimensional analysis.

The unit of physical quantity which does not depend on the unit of any other physical quantity is called as fundamental dimension. Different physical quantities which are used in fluid phenomenon are formed by these fundamental quantities.

Mass, length, time and temperature are the quantities which do not depend upon any other physical quantities. Therefore these quantities are fundamental quantities or primary quantities.

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