# Mass

inertial massgravitational massweightunit of massweighgravitationalimaginary masscomplex massinertialinertial and gravitational
Mass is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied.wikipedia
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### Force

forcesattractiveforce vector
The object's mass also determines the strength of its gravitational attraction to other bodies.
A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate.

### Inertia

inertialinertia forceinertial forces
Mass is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied.
Inertia is one of the primary manifestations of mass, which is a quantitative property of physical systems.

### Motion (physics)

motionmovementlocomotion
Mass is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied.
An object's momentum is directly related to the object's mass and velocity, and the total momentum of all objects in an isolated system (one not affected by external forces) does not change with time, as described by the law of conservation of momentum.

### Equivalence principle

strong equivalence principleequivalentPrinciple of Equivalence
This is sometimes referred to as gravitational mass. Repeated experiments since the 17th century have demonstrated that inertial and gravitational mass are identical; since 1915, this observation has been entailed a priori in the equivalence principle of general relativity.
In the theory of general relativity, the equivalence principle is the equivalence of gravitational and inertial mass, and Albert Einstein's observation that the gravitational "force" as experienced locally while standing on a massive body (such as the Earth) is the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.

### Gravitational constant

GNewton's gravitational constantuniversal gravitational constant
If a first body of mass m A is placed at a distance r (center of mass to center of mass) from a second body of mass m B, each body is subject to an attractive force F g = Gm A m B /r 2, where G = 6.67 N kg −2 m 2 is the "universal gravitational constant".
with the product of their masses and the inverse square of their distance.

### Mass–energy equivalence

mass-energy equivalencemass-energymass–energy
the electronvolt (eV) is a unit of energy, but because of the mass–energy equivalence it can easily be converted to a unit of mass, and is often used like one. In this context, the mass has units of eV/c 2 (where c is the speed of light). The electronvolt and its multiples, such as the MeV (megaelectronvolt), are commonly used in particle physics.
In physics, mass–energy equivalence states that anything having mass has an equivalent amount of energy and vice versa, with these fundamental quantities directly relating to one another by Albert Einstein's famous formula:

### Tonne

ttonnesmetric ton
the tonne (t) (or "metric ton") is equal to 1000 kg.
The tonne (Non-SI unit, symbol: t), commonly referred to as the metric ton in the United States, is a non-SI metric unit of mass equal to 1,000 kilograms; or one megagram (Mg); it is equivalent to approximately 2,204.6 pounds, 1.102 short tons (US) or 0.984 long tons (UK).

### Atomic mass unit

the atomic mass unit (u) is 1/12 of the mass of a carbon-12 atom, approximately 1.66 kg. The atomic mass unit is convenient for expressing the masses of atoms and molecules.
The unified atomic mass unit or dalton (symbol: u, or Da or AMU) is a standard unit of mass that quantifies mass on an atomic or molecular scale (atomic mass).

### Physical body

objectbodyphysical object
Mass is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied.
A physical body as a whole is assumed to have such quantitative properties as mass, momentum, electric charge, other conserving quantities, and possibly other quantities.

### Gravitational field

gravitationalgravitational fieldsgravity field
A body's mass also determines the degree to which it generates or is affected by a gravitational field.
In its original concept, gravity was a force between point masses.

### Pound (mass)

lbpoundspound
the pound (lb) is a unit of both mass and force, used mainly in the United States (about 0.45 kg or 4.5 N). In scientific contexts where pound (force) and pound (mass) need to be distinguished, SI units are usually used instead.
The pound or pound-mass is a unit of mass

### Solar mass

mass of the SunSun's masssolar masses
the solar mass is defined as the mass of the Sun. It is primarily used in astronomy to compare large masses such as stars or galaxies (≈1.99 kg).
The solar mass () is a standard unit of mass in astronomy, equal to approximately 2 kg. It is used to indicate the masses of other stars, as well as clusters, nebulae, and galaxies.

### Slug (unit)

slugslugsmetric slug
the slug (sl) is an Imperial unit of mass (about 14.6 kg).
The slug is a derived unit of mass in the weight-based system of measures, most notably within the British Imperial measurement system and in the United States customary measures system.

### Black hole

black holesblack-holeblackhole
the mass of a very large star or black hole may be identified with its Schwarzschild radius (1 cm ≈ 6.73 kg).
A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole.

### Energy

energiesenergy transfertotal energy
the electronvolt (eV) is a unit of energy, but because of the mass–energy equivalence it can easily be converted to a unit of mass, and is often used like one. In this context, the mass has units of eV/c 2 (where c is the speed of light). The electronvolt and its multiples, such as the MeV (megaelectronvolt), are commonly used in particle physics.
Mass and energy are closely related.

### Planck mass

Planck scalemassPlanck-scale
the Planck mass (m P ) is the maximum mass of point particles (about 2.18 kg). It is used in particle physics.
In physics, the Planck mass, denoted by m P, is the unit of mass in the system of natural units known as Planck units.

### International System of Units

SISI unitsSI unit
The basic SI unit of mass is the kilogram (kg).
The first letter of symbols for units derived from the name of a person is written in upper case; otherwise, they are written in lower case. E.g., the unit of pressure is named after Blaise Pascal, so its symbol is written "Pa", but the symbol for mole is written "mol". Thus, "T" is the symbol for tesla, a measure of magnetic field strength, and "t" the symbol for tonne, a measure of mass. Since 1979, the litre may exceptionally be written using either an uppercase "L" or a lowercase "l", a decision prompted by the similarity of the lowercase letter "l" to the numeral "1", especially with certain typefaces or English-style handwriting. The American NIST recommends that within the United States "L" be used rather than "l".

### Electronvolt

eVkeVMeV
the electronvolt (eV) is a unit of energy, but because of the mass–energy equivalence it can easily be converted to a unit of mass, and is often used like one. In this context, the mass has units of eV/c 2 (where c is the speed of light). The electronvolt and its multiples, such as the MeV (megaelectronvolt), are commonly used in particle physics.
By mass–energy equivalence, the electronvolt is also a unit of mass.

### Kilogram

kgmgmilligram
The basic SI unit of mass is the kilogram (kg).
The kilogram or kilogramme (symbol: kg) is the base unit of mass in the International System of Units (SI).

### Mass versus weight

weightdistinctionhistorical conflation of mass and weight
But because of slight differences in the strength of the Earth's gravitational field at different places, the distinction becomes important for measurements with a precision better than a few percent, and for places far from the surface of the Earth, such as in space or on other planets.
In common usage, the mass of an object is often referred to as its weight, though these are in fact different concepts and quantities.

### Acceleration

decelerationacceleratem/s 2
Mass is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied.
where F is the net force acting on the body, m is the mass of the body, and a is the center-of-mass acceleration.

### Gravitational time dilation

freezing both in timegoes more slowlygravity's effect on time
Curvature of spacetime is a relativistic manifestation of the existence of mass. Such curvature is extremely weak and difficult to measure. For this reason, curvature was not discovered until after it was predicted by Einstein's theory of general relativity. Extremely precise atomic clocks on the surface of the Earth, for example, are found to measure less time (run slower) when compared to similar clocks in space. This difference in elapsed time is a form of curvature called gravitational time dilation. Other forms of curvature have been measured using the Gravity Probe B satellite.
Gravitational time dilation is a form of time dilation, an actual difference of elapsed time between two events as measured by observers situated at varying distances from a gravitating mass.

### Measure (mathematics)

measuremeasure theorymeasurable
Mass is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied.
In physics an example of a measure is spatial distribution of mass (see e.g., gravity potential), or another non-negative extensive property, conserved (see conservation law for a list of these) or not.

### Compton wavelength

Compton recoilcorresponding energywavelength
the mass of a very small particle may be identified by its inverse Compton wavelength (1 cm −1 ≈ 3.52 kg).
is the particle's mass, and

### Gravity of Earth

ggravityEarth's gravity
But because of slight differences in the strength of the Earth's gravitational field at different places, the distinction becomes important for measurements with a precision better than a few percent, and for places far from the surface of the Earth, such as in space or on other planets.
The gravity of Earth, denoted by, is the net acceleration that is imparted to objects due to the combined effect of gravitation (from distribution of mass within Earth) and the centrifugal force (from the Earth's rotation).