# Volume

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Volume
A measuring cup can be used to measure volumes of liquids. This cup measures volume in units of cups, fluid ounces, and millilitres.
Common symbols
V
SI unit Cubic metre [m3]
Other units
Litre, fluid ounce, gallon, quart, pint, tsp, fluid dram, in3, yd3, barrel
In SI base units 1  m 3
Dimension L3

Volume is the quantity of three-dimensional space enclosed by a closed surface, for example, the space that a substance (solid, liquid, gas, or plasma) or 3D shape occupies or contains. [1] Volume is often quantified numerically using the SI derived unit, the cubic metre. The volume of a container is generally understood to be the capacity of the container; i.e., the amount of fluid (gas or liquid) that the container could hold, rather than the amount of space the container itself displaces. Three dimensional mathematical shapes are also assigned volumes. Volumes of some simple shapes, such as regular, straight-edged, and circular shapes can be easily calculated using arithmetic formulas . Volumes of complicated shapes can be calculated with integral calculus if a formula exists for the shape's boundary. One-dimensional figures (such as lines) and two-dimensional shapes (such as squares) are assigned zero volume in the three-dimensional space.

## Contents

The volume of a solid (whether regularly or irregularly shaped) can be determined by fluid displacement. Displacement of liquid can also be used to determine the volume of a gas. The combined volume of two substances is usually greater than the volume of just one of the substances. However, sometimes one substance dissolves in the other and in such cases the combined volume is not additive. [2]

In differential geometry , volume is expressed by means of the volume form, and is an important global Riemannian invariant. In thermodynamics , volume is a fundamental parameter, and is a conjugate variable to pressure.

## Units

Any unit of length gives a corresponding unit of volume: the volume of a cube whose sides have the given length. For example, a cubic centimetre (cm3) is the volume of a cube whose sides are one centimetre (1 cm) in length.

In the International System of Units (SI), the standard unit of volume is the cubic metre (m3). The metric system also includes the litre (L) as a unit of volume, where one litre is the volume of a 10-centimetre cube. Thus

1 = (10 cm)3 = 1000 cubic centimetres = 0.001 cubic metres,

so

1 cubic metre = 1000 litres.

Small amounts of liquid are often measured in millilitres, where

1 millilitre = 0.001 litres = 1 cubic centimetre.

In the same way, large amounts can be measured in megalitres, where

1 million litres = 1000 cubic metres = 1 megalitre.

Various other traditional units of volume are also in use, including the cubic inch, the cubic foot, the cubic yard, the cubic mile, the teaspoon, the tablespoon, the fluid ounce, the fluid dram, the gill, the pint, the quart, the gallon, the minim, the barrel, the cord, the peck, the bushel, the hogshead, the acre-foot and the board foot. This are all units of volume.

Capacity is defined by the Oxford English Dictionary as "the measure applied to the content of a vessel, and to liquids, grain, or the like, which take the shape of that which holds them". [4] (The word capacity has other unrelated meanings, as in e.g. capacity management.) Capacity is not identical in meaning to volume, though closely related; the capacity of a container is always the volume in its interior. Units of capacity are the SI litre and its derived units, and Imperial units such as gill, pint, gallon, and others. Units of volume are the cubes of units of length. In SI the units of volume and capacity are closely related: one litre is exactly 1 cubic decimetre, the capacity of a cube with a 10 cm side. In other systems the conversion is not trivial; the capacity of a vehicle's fuel tank is rarely stated in cubic feet, for example, but in gallons (an imperial gallon fills a volume with 0.1605 cu ft).

The density of an object is defined as the ratio of the mass to the volume. [5] The inverse of density is specific volume which is defined as volume divided by mass. Specific volume is a concept important in thermodynamics where the volume of a working fluid is often an important parameter of a system being studied.

The volumetric flow rate in fluid dynamics is the volume of fluid which passes through a given surface per unit time (for example cubic meters per second [m3 s−1]).

## Calculus

In calculus, a branch of mathematics, the volume of a region D in R3 is given by a triple integral of the constant function ${\displaystyle f(x,y,z)=1}$ over the region and is usually written as:

${\displaystyle \iiint \limits _{D}1\,dx\,dy\,dz.}$

In cylindrical coordinates, the volume integral is

${\displaystyle \iiint \limits _{D}r\,dr\,d\theta \,dz,}$

In spherical coordinates (using the convention for angles with ${\displaystyle \theta }$ as the azimuth and ${\displaystyle \varphi }$ measured from the polar axis; see more on conventions), the volume integral is

${\displaystyle \iiint \limits _{D}\rho ^{2}\sin \varphi \,d\rho \,d\theta \,d\varphi .}$

## Formulas

ShapeVolume formulaVariables
Cube ${\displaystyle V=a^{3}\;}$
Cuboid ${\displaystyle V=abc}$
Prism

(B: area of base)

${\displaystyle V=Bh}$
Pyramid

(B: area of base)

${\displaystyle V={\frac {1}{3}}Bh}$
Parallelepiped ${\displaystyle V=abc{\sqrt {K}}}$

{\displaystyle {\begin{aligned}K=1&+2\cos(\alpha )\cos(\beta )\cos(\gamma )\\&-\cos ^{2}(\alpha )-\cos ^{2}(\beta )-\cos ^{2}(\gamma )\end{aligned}}}

Regular tetrahedron ${\displaystyle V={{\sqrt {2}} \over 12}a^{3}\,}$
Sphere ${\displaystyle V={\frac {4}{3}}\pi r^{3}}$
Ellipsoid ${\displaystyle V={\frac {4}{3}}\pi abc}$
Circular Cylinder ${\displaystyle V=\pi r^{2}h}$
Cone ${\displaystyle V={\frac {1}{3}}\pi r^{2}h}$
Solid torus ${\displaystyle V=2\pi ^{2}Rr^{2}}$
Solid of revolution ${\displaystyle V=\pi \cdot \int _{a}^{b}f(x)^{2}\mathrm {d} x}$
Solid body with continuous area

${\displaystyle A(x)}$ of its cross sections
(example: Steinmetz solid)

${\displaystyle V=\int _{a}^{b}A(x)\mathrm {d} x}$For the solid of revolution above:

${\displaystyle A(x)=\pi f(x)^{2}}$

### Ratios for a cone, sphere and cylinder of the same radius and height

The above formulas can be used to show that the volumes of a cone, sphere and cylinder of the same radius and height are in the ratio 1 : 2 : 3, as follows.

Let the radius be r and the height be h (which is 2r for the sphere), then the volume of the cone is

${\displaystyle {\frac {1}{3}}\pi r^{2}h={\frac {1}{3}}\pi r^{2}\left(2r\right)=\left({\frac {2}{3}}\pi r^{3}\right)\times 1,}$

the volume of the sphere is

${\displaystyle {\frac {4}{3}}\pi r^{3}=\left({\frac {2}{3}}\pi r^{3}\right)\times 2,}$

while the volume of the cylinder is

${\displaystyle \pi r^{2}h=\pi r^{2}(2r)=\left({\frac {2}{3}}\pi r^{3}\right)\times 3.}$

The discovery of the 2 : 3 ratio of the volumes of the sphere and cylinder is credited to Archimedes. [6]

### Formula derivations

#### Sphere

The volume of a sphere is the integral of an infinite number of infinitesimally small circular disks of thickness dx. The calculation for the volume of a sphere with center 0 and radius r is as follows.

The surface area of the circular disk is ${\displaystyle \pi r^{2}}$.

The radius of the circular disks, defined such that the x-axis cuts perpendicularly through them, is

${\displaystyle y={\sqrt {r^{2}-x^{2}}}}$

or

${\displaystyle z={\sqrt {r^{2}-x^{2}}}}$

where y or z can be taken to represent the radius of a disk at a particular x value.

Using y as the disk radius, the volume of the sphere can be calculated as

${\displaystyle \int _{-r}^{r}\pi y^{2}\,dx=\int _{-r}^{r}\pi \left(r^{2}-x^{2}\right)\,dx.}$

Now

${\displaystyle \int _{-r}^{r}\pi r^{2}\,dx-\int _{-r}^{r}\pi x^{2}\,dx=\pi \left(r^{3}+r^{3}\right)-{\frac {\pi }{3}}\left(r^{3}+r^{3}\right)=2\pi r^{3}-{\frac {2\pi r^{3}}{3}}.}$

Combining yields ${\displaystyle V={\frac {4}{3}}\pi r^{3}.}$

This formula can be derived more quickly using the formula for the sphere's surface area, which is ${\displaystyle 4\pi r^{2}}$. The volume of the sphere consists of layers of infinitesimally thin spherical shells, and the sphere volume is equal to

${\displaystyle \int _{0}^{r}4\pi r^{2}\,dr={\frac {4}{3}}\pi r^{3}.}$

#### Cone

The cone is a type of pyramidal shape. The fundamental equation for pyramids, one-third times base times altitude, applies to cones as well.

However, using calculus, the volume of a cone is the integral of an infinite number of infinitesimally thin circular disks of thickness dx. The calculation for the volume of a cone of height h, whose base is centered at (0, 0, 0) with radius r, is as follows.

The radius of each circular disk is r if x = 0 and 0 if x = h, and varying linearly in between—that is,

${\displaystyle r{\frac {h-x}{h}}.}$

The surface area of the circular disk is then

${\displaystyle \pi \left(r{\frac {h-x}{h}}\right)^{2}=\pi r^{2}{\frac {(h-x)^{2}}{h^{2}}}.}$

The volume of the cone can then be calculated as

${\displaystyle \int _{0}^{h}\pi r^{2}{\frac {(h-x)^{2}}{h^{2}}}dx,}$

and after extraction of the constants

${\displaystyle {\frac {\pi r^{2}}{h^{2}}}\int _{0}^{h}(h-x)^{2}dx}$

Integrating gives us

${\displaystyle {\frac {\pi r^{2}}{h^{2}}}\left({\frac {h^{3}}{3}}\right)={\frac {1}{3}}\pi r^{2}h.}$

## Differential geometry

In differential geometry, a branch of mathematics, a volume form on a differentiable manifold is a differential form of top degree (i.e., whose degree is equal to the dimension of the manifold) that is nowhere equal to zero. A manifold has a volume form if and only if it is orientable. An orientable manifold has infinitely many volume forms, since multiplying a volume form by a non-vanishing function yields another volume form. On non-orientable manifolds, one may instead define the weaker notion of a density. Integrating the volume form gives the volume of the manifold according to that form.

An oriented pseudo-Riemannian manifold has a natural volume form. In local coordinates, it can be expressed as

${\displaystyle \omega ={\sqrt {|g|}}\,dx^{1}\wedge \dots \wedge dx^{n},}$

where the ${\displaystyle dx^{i}}$ are 1-forms that form a positively oriented basis for the cotangent bundle of the manifold, and ${\displaystyle g}$ is the determinant of the matrix representation of the metric tensor on the manifold in terms of the same basis.

## Thermodynamics

In thermodynamics, the volume of a system is an important extensive parameter for describing its thermodynamic state. The specific volume, an intensive property, is the system's volume per unit of mass. Volume is a function of state and is interdependent with other thermodynamic properties such as pressure and temperature. For example, volume is related to the pressure and temperature of an ideal gas by the ideal gas law.

## Computation

The task of numerically computing the volume of objects is studied in the field of computational geometry in computer science, investigating efficient algorithms to perform this computation, approximately or exactly, for various types of objects. For instance, the convex volume approximation technique shows how to approximate the volume of any convex body using a membership oracle.

## Related Research Articles

Area is the quantity that expresses the extent of a two-dimensional region, shape, or planar lamina, in the plane. Surface area is its analog on the two-dimensional surface of a three-dimensional object. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat. It is the two-dimensional analog of the length of a curve or the volume of a solid.

A sphere is a geometrical object in three-dimensional space that is the surface of a ball.

In mathematics, an n-sphere is a topological space that is homeomorphic to a standardn-sphere, which is the set of points in (n + 1)-dimensional Euclidean space that are situated at a constant distance r from a fixed point, called the center. It is the generalization of an ordinary sphere in the ordinary three-dimensional space. The "radius" of a sphere is the constant distance of its points to the center. When the sphere has unit radius, it is usual to call it the unit n-sphere or simply the n-sphere for brevity. In terms of the standard norm, the n-sphere is defined as

In mathematics, a 3-sphere, or glome, is a higher-dimensional analogue of a sphere. It may be embedded in 4-dimensional Euclidean space as the set of points equidistant from a fixed central point. Analogous to how the boundary of a ball in three dimensions is an ordinary sphere, the boundary of a ball in four dimensions is a 3-sphere. A 3-sphere is an example of a 3-manifold and an n-sphere.

In geometry, a solid angle is a measure of the amount of the field of view from some particular point that a given object covers. That is, it is a measure of how large the object appears to an observer looking from that point. The point from which the object is viewed is called the apex of the solid angle, and the object is said to subtend its solid angle from that point.

In mathematics, a ball is the volume space bounded by a sphere; it is also called a solid sphere. It may be a closed ball or an open ball.

The Method of Mechanical Theorems, also referred to as The Method, is considered one of the major surviving works of the ancient Greek polymath Archimedes. The Method takes the form of a letter from Archimedes to Eratosthenes, the chief librarian at the Library of Alexandria, and contains the first attested explicit use of indivisibles. The work was originally thought to be lost, but in 1906 was rediscovered in the celebrated Archimedes Palimpsest. The palimpsest includes Archimedes' account of the "mechanical method", so called because it relies on the law of the lever, which was first demonstrated by Archimedes, and of the center of mass, which he had found for many special shapes.

In mathematics, engineering, and manufacturing, a solid of revolution is a solid figure obtained by rotating a plane curve around some straight line that lies on the same plane.

A cone is a three-dimensional geometric shape that tapers smoothly from a flat base to a point called the apex or vertex.

A cylinder has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. It is the idealized version of a solid physical tin can having lids on top and bottom. Geometrically, it can be considered as a prism with a circle as its base.

In geometry, a spherical cap or spherical dome is a portion of a sphere or of a ball cut off by a plane. It is also a spherical segment of one base, i.e., bounded by a single plane. If the plane passes through the center of the sphere, so that the height of the cap is equal to the radius of the sphere, the spherical cap is called a hemisphere.

In geometry, the area enclosed by a circle of radius r is πr2. Here the Greek letter π represents the constant ratio of the circumference of any circle to its diameter, approximately equal to 3.1416.

In classical mechanics, the shell theorem gives gravitational simplifications that can be applied to objects inside or outside a spherically symmetrical body. This theorem has particular application to astronomy.

In mathematics, a multiple integral is a definite integral of a function of several real variables, for instance, f(x, y) or f(x, y, z). Integrals of a function of two variables over a region in are called double integrals, and integrals of a function of three variables over a region in are called triple integrals. For multiple integrals of a single-variable function, see the Cauchy formula for repeated integration.

In geometry, a hypercone is the figure in the 4-dimensional Euclidean space represented by the equation

In differential geometry, Pu's inequality, proved by Pao Ming Pu, relates the area of an arbitrary Riemannian surface homeomorphic to the real projective plane with the lengths of the closed curves contained in it.

In geometry, a ball is a region in space comprising all points within a fixed distance from a given point; that is, it is the region enclosed by a sphere or hypersphere. An n-ball is a ball in n-dimensional Euclidean space. The volume of a unit n-ball is an important expression that occurs in formulas throughout mathematics; it generalizes the notion of the volume enclosed by a sphere in 3-dimensional space.

In mathematics, a unit sphere is simply a sphere of radius one around a given center. More generally, it is the set of points of distance 1 from a fixed central point, where different norms can be used as general notions of "distance". A unit ball is the closed set of points of distance less than or equal to 1 from a fixed central point. Usually the center is at the origin of the space, so one speaks of "the" unit ball or "the" unit sphere. Special cases are the unit circle and the unit disk.

The Derjaguin approximation due to the Russian scientist Boris Derjaguin expresses the force profile acting between finite size bodies in terms of the force profile between two planar semi-infinite walls. This approximation is widely used to estimate forces between colloidal particles, as forces between two planar bodies are often much easier to calculate. The Derjaguin approximation expresses the force F(h) between two bodies as a function of the surface separation as

In four-dimensional geometry, the spherinder, or spherical cylinder or spherical prism, is a geometric object, defined as the Cartesian product of a 3-ball, radius r1 and a line segment of length 2r2:

## References

1. "Your Dictionary entry for "volume"" . Retrieved 2010-05-01.
2. One litre of sugar (about 970 grams) can dissolve in 0.6 litres of hot water, producing a total volume of less than one litre. "Solubility" . Retrieved 2010-05-01. Up to 1800 grams of sucrose can dissolve in a liter of water.
3. "General Tables of Units of Measurement". NIST Weights and Measures Division. Archived from the original on 2011-12-10. Retrieved 2011-01-12.
4. . Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
5. . Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
6. Rorres, Chris. "Tomb of Archimedes: Sources". Courant Institute of Mathematical Sciences. Retrieved 2007-01-02.