What is a dimensionless quantity? give examples

A dimensionless quantity is a quantity that does not have any physical dimensions and is expressed as a pure number without any units.

Examples of Dimensionless Quantities:

• Pi (π): The ratio of the circumference of a circle to its diameter.
• Reynolds Number (Re): A measure of the relative importance of inertial forces to viscous forces in fluid flow.
• Strain: The ratio of the change in length to the original length of a material.
• Coefficient of Friction: The ratio of the force of friction between two bodies to the normal force pressing them together.
• Relative Density (Specific Gravity): The ratio of the density of a substance to the density of a reference substance (typically water).

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