91Ó°ÊÓ

Dimensionless physical quantities are physical quantities that cannot be expressed as a power of the dimensions of basic physical quantities.

Following are examples of physical quantities that have units but are dimensionless:

Mach number – Mach number is a dimensionless quantity; it is the ratio of the speed of flow at a certain point to the speed of sound in that fluid medium.

Deformation – Deformation is a physical quantity that indicates the relative change in size and shape of an object due to external forces.

Reynolds number - Reynolds number is a dimensionless quantity, obtained by the ratio of inertial forces and viscous forces; since it is a ratio of two forces, it is a dimensionless quantity.

Here, v is the velocity of an object, c is the speed of light, data-custom-editor="chemistry" $∆\mathrm{l}$is the change in length, l is the original length of an object, Reynolds numbers is the density of the fluid, u is the flow speed, L is the characteristic linear dimension, and data-custom-editor="chemistry" $\mathrm{μ}$is the dynamic viscosity of the fluid.

Hence, here above explain 3 physical quantities.