Introduction to Units and Dimensions

Every measurement has two parts: a number (n) and a unit (u). The equation for this is Q = nu. For example, the length of an object is expressed as 40 cm, where the number expressing the magnitude of the physical quantity is inversely proportional to the unit selected.

If n1 and n2 are the numerical values of a physical quantity corresponding to the units u1 and u2, then n1u1 = n2u2.
For Example: 2.8 m = 280 cm; 6.2 kg = 6200 g.

Table of Contents

Units of Physical Quantities

What are Dimensions?

What is the Dimensional Formula?

Limitations of Dimensional Analysis

Important Physical Constants

Dimensional Formulas for Physical Quantities

Quantities Having Same Dimensional Formula

Applications of Dimensional Analysis

Frequently Asked Questions on Dimension Analysis

Fundamental and Derived Quantities

Fundamental quantities are those that are independent of other quantities. The fundamental units used to measure these quantities are divided into four systems of units: C.G.S, M.K.S, F.P.S, and SI.

Derived Quantities are quantities that are derived from the fundamental quantities. The Derived Units used to measure these derived quantities are also derived from the fundamental units.

Fundamental and Supplementary Physical Quantities in the SI System

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Introduction to Units and Dimensions

Every measurement has two parts. The first is a number (n), and the next is a unit (u). Q = n*u. For Example, the length of an object = 40 cm. The number expressing the magnitude of a physical quantity is inversely proportional to the unit selected.

If n1 and n2 are the numerical values of a physical quantity corresponding to the units u1 and u2, then it can be said that n1u1 = n2u2. For example, 2.8 m = 280 cm; 6.2 kg = 6200 g.

Table of Contents

Units of Physical Quantities

What are Dimensions?

What is the Dimensional Formula?

Limitations of Dimensional Analysis

Important Physical Constants

Dimensional Formulas for Physical Quantities

Quantities Having Same Dimensional Formula

Applications of Dimensional Analysis

Frequently Asked Questions on Dimension Analysis

Fundamental and Derived Quantities

Fundamental quantities are those that are independent of other quantities. The units used to measure these fundamental quantities are known as fundamental units. There are four systems of units, namely C.G.S, M.K.S, F.P.S, and SI.

The quantities derived from the fundamental quantities are referred to as derived quantities, and the units used to measure these derived quantities are called derived units.

Fundamental Physical Quantities in the SI System

1. Length
2. Mass
3. Time
4. Electric current
5. Temperature
6. Amount of substance
7. Luminous intensity

Supplementary Physical Quantities in the SI System

1. Plane angle
2. Solid angle
3. Frequency
4. Force
5. Pressure
6. Energy
7. Power

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