on . Posted in Classical Mechanics

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Mass, abbreviated as m, is the amount of matter an object has.  It is the property of a body that causes it to have weight in a gravitational field.  It is sometimes used interchangeably in place of weight.  Mass is a scalar quantity having magnitude and is independent of any specific direction.

Weight is a vector quantity that depends on the gravity at a specific location.  The mass of an object is different from its weight, which is the force exerted on the object by gravity.  Mass is a fundamental property of matter, whereas weight is dependent on the object's mass and the acceleration due to gravity.

Mass Types

  • Gravitational Mass  -  The mass of an object as measured by its interaction with gravity, it is equal to its inertial mass.
  • Internal Mass  -  The mass of an object measured by its resistance to acceleration when a force is applied.
  • Invariant Mass  -  The inferred value of the mass is independent of the reference frame in which the energies and momentum are measured so that the mass is invariant.
  • Mass Diffusivity  -  A proportionality constant between the molar flux due to molecular diffusion and the gradient in the concentration of the species.
  • Molar Mass  -  The mass of a given compound equal to its molecular mass in gram.
  • Relativity Mass  -  The mass of a body in motion relative to the observer.
  • Rest Mass  -  Rest mass of a body is measured when the body is at rest and motionless and is also relative to an observer moving or not moving.


Mass formula

\(\large{ m = \rho \; V  }\)     (Mass)

\(\large{ \rho =  \frac{ m }{ V }  }\) 

\(\large{ V =  \frac{ m }{ \rho }  }\) 

Solve for m

density, ρ
volume, V

Solve for ρ

mass, m
volume, V

Solve for V

mass, m
density, ρ

Symbol English Metric
\(\large{ m }\) = mass \(\large{lbm}\) \(\large{kg}\)
\(\large{ \rho }\)   (Greek symbol rho) = density \(\large{\frac{lbm}{ft^3}}\) \(\large{\frac{kg}{m^3}}\)
\(\large{ V }\) = volume \(\large{ft^3}\) \(\large{m^3}\)


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Tags: Mass