# Mass

on . Posted in Classical Mechanics

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

$$m \;=\; \rho \; V$$     (Mass)

$$\rho \;=\; m \;/\; V$$

$$V \;=\; m \;/\; \rho$$

Symbol English Metric
$$m$$ = Mass $$lbm$$ $$kg$$
$$\rho$$   (Greek symbol rho) = Density $$lbm \;/\; ft^3$$ $$kg \;/\; m^3$$
$$V$$ = Volume $$ft^3$$ $$m^3$$

Tags: Mass