The ratio of inertia force and gravitational force is called

Explanation:

• Forces encountered in flowing fluids include those due to inertia, viscosity, pressure, gravity, surface tension, and compressibility.

These forces can be written as follows:

Froude number (Fr): 

• It is defined as the ratio of inertia force to gravity force.         
• \({\rm{Fr = }}\frac{{\rm{V}}}{{\sqrt {{\rm{gL}}} }}\)

Reynolds number (Re): ​​

• It is defined as the ratio of inertia force to viscous force.
• \(R_e = {{V\times d} \over \nu}\)

Weber number (We): 

• It is defined as the ratio of the inertia force to the surface tension force.
• \({\rm{We = }}\frac{{{\rm{\rho }}{{\rm{V}}^{\rm{2}}}{\rm{l}}}}{{\rm{\sigma }}}\)

Mach number (M):

• It is defined as the ratio of inertia force to the velocity of sound.
• \(M = \frac{V}{c} = \frac{V}{{\sqrt {\frac{{dP}}{{d\rho }}} }}\)