# Physics

## Degenerate matter

Degenerate matter is a highly dense state of fermionic matter in which particles must occupy high states of kinetic energy in order to satisfy the Pauli exclusion principle. Under extremely high pressure, as in the cores of dead stars, ordinary matter undergoes a transition to a series of exotic states of matter collectively known as degenerate matter, which …

## Quark matter (QCD)

Quark matter or QCD matter refers to any of a number of theorized states of matter whose degrees of freedom include quarks and gluons. In regular cold matter, quarks, fundamental particles of nuclear matter, are confined by the strong force into hadrons that consist of 2-4 quarks, such as protons and neutrons. Quark matter or quantum chromodynanamical (QCD) matter is …

## Negative mass

Negative mass is a hypothetical counterpart to ordinary (positive) mass. Such matter would violate one or more energy conditions and show some strange properties, stemming from the ambiguity as to whether attraction should refer to force or the oppositely oriented acceleration for negative mass. Although it is not known if negative mass exists, or even if its existence is …

## Center of mass

The center of mass of an object is the point at which the object can be balanced. Mathematically, it is the point at which the torques from the mass elements of an object sum to zero. The center of mass is useful because problems can often be simplified by treating a collection of masses as one mass …

## Kilogram (unit of mass)

The international prototype of the kilogram, an artifact made of platinum-iridium, is kept at the BIPM under the conditions specified by the 1st CGPM in 1889 when it sanctioned the prototype and declared: this prototype shall henceforth be considered to be the unit of mass. The 3rd CGPM (1901), in a declaration intended to end the …

## Relative motion

Relative motion is the study of the motion of an object with regard to some other moving object. Thus, the motion is not calculated with reference to the earth but is the velocity of the object in reference to the other moving object as if it were in a static state. Normally the reference system used …

## Heat transfer

Heat transfer is classified into various mechanisms, the fundamentals are: Advection: is the transport mechanism of a fluid from one location to another, and is dependent on the motion and momentum of that fluid. Thermal conduction or diffusion: the transfer of energy between objects that are in physical contact. Thermal conductivity is the property of …

## Heat flux

Heat flux (or thermal flux, sometimes also referred to as heat flux density or heat flow rate intensity) is a flow of thermal energy per unit of area per unit of time. $\vec{\phi}_q\;\left[\dfrac{\textrm{W}}{\textrm{m}^2}\right]$ the subscript $$q$$ specifying heat flux, as opposed to mass or momentum flux. Fourier’s law is an important application of these concepts. It has both a direction and a magnitude, and so it is a vector quantity. To define the heat …

## Heat capacity

Heat capacity (C) also called thermal capacity, is the amount of heat needed to raise the temperature of an object through 1 °C, either at constant pressure or at constant volume and without inducing chemical changes or a change of phase. Numerically it is equal to the product of the mass (m) of the object and …