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[[File:Simple Measuring Cup.jpg|thumb|A [[measuring cup]] can be used to measure volumes of [[liquid]]s. This cup measures volume in units of [[Cup (unit)|cups]], [[fluid ounce]]s, and [[millilitre]]s.]]<br />
'''Volume''' is the [[quantity]] of [[three-dimensional space]] enclosed by some closed boundary, for example, the space that a substance ([[solid]], [[liquid]], [[gas]], or [[Plasma (physics)|plasma]]) or shape occupies or contains.<ref><br />
{{cite web |url=http://www.yourdictionary.com/volume |title= Your Dictionary entry for "volume" |accessdate=2010-05-01}}<br />
</ref><br />
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.<br />
<br />
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]] [[formula]]s<!--- both "formulae" and "formulas" are correct plurals of "formula" --->. Volumes of a complicated shape can be calculated by [[integral calculus]] if a formula exists for the shape's boundary. Where a variance in shape and volume occurs, such as those that exist between different human beings, these can be calculated using three-dimensional techniques such as the [[Body Volume Index]]. One-dimensional figures (such as [[line (mathematics)|lines]]) and two-dimensional shapes (such as [[square (geometry)|squares]]) are assigned zero volume in the three-dimensional space.<br />
<br />
The volume of a solid (whether regularly or irregularly shaped) can be determined by [[Displacement (fluid)|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 one of the substances. However, sometimes one substance dissolves in the other and the combined volume is not [[additive map|additive]].<ref>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. {{cite web |url=http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch18/soluble.php |title=Solubility |accessdate=2010-05-01 |quote=Up to 1800 grams of sucrose can dissolve in a liter of water.}}</ref><br />
<br />
In ''[[differential geometry]]'', volume is expressed by means of the [[volume form]], and is an important global [[Riemannian geometry|Riemannian]] [[Invariant (mathematics)|invariant]].<br />
In ''[[thermodynamics]]'', volume is a [[gas volume|fundamental parameter]], and is a [[conjugate variables (thermodynamics)|conjugate variable]] to [[pressure]].<br />
<br />
==Units==<br />
[[File:Volume measurements from The New Student's Reference Work.svg|thumb|220px|Volume measurements from the 1914 [[s:The New Student's Reference Work|The New Student's Reference Work]].<br/><br />
'''Approximate conversion to millilitres:'''<ref>{{cite web |url=http://ts.nist.gov/WeightsAndMeasures/Publications/appxc.cfm#4e |title=General Tables of Units of Measurement |author= |date= |work= |publisher=NIST Weights and Measures Division |accessdate=2011-01-12}}</ref><br />
{| style="width:200px;"<br />
|-<br />
! !! Imperial !! U.S. liquid !! U.S. dry<br />
|-<br />
| [[Gill (unit)|Gill]] || 142 mL || 118 mL || 138 mL<br />
|-<br />
| [[Pint]] || 568 mL || 473 mL || 551 mL<br />
|-<br />
| [[Quart]] || 1137 mL || 946 mL || 1101 mL<br />
|-<br />
| [[Gallon]] || 4546 mL || 3785 mL || 4405 mL<br />
|}<br />
]]<br />
Any unit of [[length]] gives a corresponding unit of volume, namely the volume of a [[cube]] whose side has the given length. For example, a [[cubic centimetre]] (cm<sup>3</sup>) would be the volume of a cube whose sides are one [[centimetre]] (1&nbsp;cm) in length.<br />
<br />
In the [[International System of Units]] (SI), the standard unit of volume is the cubic metre (m<sup>3</sup>). 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<br />
:1 litre = (10 cm)<sup>3</sup> = 1000 cubic centimetres = 0.001 cubic metres,<br />
<br />
so<br />
:1 cubic metre = 1000 litres.<br />
Small amounts of liquid are often measured in [[millilitre]]s, where<br />
:1 millilitre = 0.001 litres = 1 cubic centimetre.<br />
<br />
Various other traditional units of volume are also in use, including the [[cubic inch]], the [[cubic foot]], the [[cubic mile]], the [[teaspoon]], the [[tablespoon]], the [[fluid ounce]], the [[fluid dram]], the [[gill (volume)|gill]], the [[pint]], the [[quart]], the [[gallon]], the [[minim (unit)|minim]], the [[barrel (unit)|barrel]], the [[cord (unit)|cord]], the [[peck]], the [[bushel]], and the [[hogshead]].<br />
<br />
== Related terms ==<br />
Volume and ''capacity'' are sometimes distinguished, with capacity being used for how much a container can hold (with contents measured commonly in [[litre]]s or its derived units), and volume being how much space an object displaces (commonly measured in cubic metres or its derived units).<br />
<br />
Volume and capacity are also distinguished in [[capacity management]], where capacity is defined as volume over a specified time period. However, in this context the term volume may be more loosely interpreted to mean ''quantity''.<br />
<br />
The ''[[density]]'' of an object is defined as mass per unit volume. 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 (thermodynamics)|volume of a working fluid]] is often an important parameter of a system being studied.<br />
<br />
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 [m<sup>3</sup> s<sup>−1</sup>]).<br />
<br />
== Volume in calculus ==<br />
<br />
In [[calculus]], a branch of [[mathematics]], the volume of a region ''D'' in '''R'''<sup>3</sup> is given by a [[multiple integral|triple integral]] of the constant [[function (mathematics)|function]] <math>f(x,y,z)=1</math> and is usually written as:<br />
<br />
:<math>\iiint\limits_D 1 \,dx\,dy\,dz.</math><br />
<br />
The volume integral in [[cylindrical coordinates]] is<br />
<br />
:<math>\iiint\limits_D r\,dr\,d\theta\,dz, </math><br />
<br />
and the volume integral in [[spherical coordinates]] (using the convention for angles with <math>\theta</math> as the azimuth and <math>\phi</math> measured from the polar axis (see more on [[Spherical coordinate system#Conventions|conventions]])) has the form<br />
<br />
:<math>\iiint\limits_D \rho^2 \sin\phi \,d\rho \,d\theta\, d\phi .</math><br />
<br />
== Volume formulas ==<br />
{| class="wikitable"<br />
|-<br />
!Shape || Volume formula || Variables<br />
|-<br />
|[[Cube (geometry)|Cube]] <br />
|style="text-align:center"|<math>a^3\;</math><br />
|''a'' = length of any side (or edge)<br />
|-<br />
|[[cylinder (geometry)|Cylinder]]<br />
|style="text-align:center"|<math>\pi r^2 h\;</math> <br />
|''r'' = radius of circular face, ''h'' = height<br />
|-<br />
|[[Prism (geometry)|Prism]]<br />
|style="text-align:center"|<math>B \cdot h</math><br />
|''B'' = area of the base, ''h'' = height<br />
|-<br />
|[[Rectangular prism]]<br />
|style="text-align:center"|<math>l \cdot w \cdot h</math><br />
|l = length, w = width, h = height<br />
|-<br />
|[[Triangular prism]]<br />
|style="text-align:center"|<math>\frac{1}{2}bhl</math><br />
|''b'' = base length of triangle, ''h'' = height of triangle, ''l'' = length of prism or distance between the triangular bases<br />
|-<br />
|[[Sphere]]<br />
|style="text-align:center"|<math>\frac{4}{3} \pi r^3</math> <br />
|''r'' = radius of sphere<br>which is the [[integral]] of the [[surface area]] of a sphere<br />
|-<br />
|[[Ellipsoid]]<br />
|style="text-align:center"|<math>\frac{4}{3} \pi abc</math> <br />
|''a'', ''b'', ''c'' = semi-axes of ellipsoid<br />
|-<br />
|[[Torus]]<br />
|style="text-align:center"|<math>(\pi r^2)(2\pi R) = 2\pi^2 Rr^2</math><br />
|''r'' = minor radius (radius of the tube), ''R'' = major radius (distance from center of tube to center of torus)<br />
|-<br />
|[[Pyramid (geometry)|Pyramid]]<br />
|style="text-align:center"|<math>\frac{1}{3}Bh</math><br />
|''B'' = area of the base, ''h'' = height of pyramid<br />
|-<br />
|[[Square pyramid]]<br />
|style="text-align:center"|<math>\frac{1}{3} s^2 h\;</math> <br />
|''s'' = side length of base, ''h'' = height<br />
|-<br />
|[[Rectangular]] [[Pyramid (geometry)|pyramid]]<br />
|style="text-align:center"|<math>\frac{1}{3} lwh</math><br />
|l = length, w = width, h = height<br />
|-<br />
|[[Cone (geometry)|Cone]]<br />
|style="text-align:center"|<math>\frac{1}{3} \pi r^2 h</math><br />
|''r'' = radius of [[circle]] at base, ''h'' = distance from base to tip or height<br />
|-<br />
|[[Tetrahedron]]<ref name=Cox>[[H. S. M. Coxeter|Coxeter, H. S. M.]]: ''[[Regular Polytopes (book)|Regular Polytopes]]'' (Methuen and Co., 1948). Table I(i).</ref><br />
|style="text-align:center"|<math>{\sqrt{2}\over12}a^3 \,</math><br />
|edge length <math>a</math><br />
|-<br />
|[[Parallelepiped]]<br />
|style="text-align:center"|<math><br />
a b c \sqrt{K}<br />
</math><br />
<br/><br />
<math><br />
\begin{align}<br />
K =& 1+2\cos(\alpha)\cos(\beta)\cos(\gamma) \\<br />
& - \cos^2(\alpha)-\cos^2(\beta)-\cos^2(\gamma)<br />
\end{align}<br />
</math><br />
|''a'', ''b'', and ''c'' are the parallelepiped edge lengths, and α, β, and γ are the internal angles between the edges<br />
|-<br />
|Any volumetric sweep<br/>([[integral calculus|calculus]] required)<br />
|style="text-align:center"|<math>\int_a^b A(h) \,\mathrm{d}h</math><br />
|''h'' = any dimension of the figure,<br/>''A''(''h'') = area of the cross-sections perpendicular to ''h'' described as a function of the position along ''h''. ''a'' and ''b'' are the limits of integration for the volumetric sweep.<br/>(This will work for any figure if its cross-sectional area can be determined from h).<br />
|-<br />
|Any rotated figure (washer method)<br/>([[integral calculus|calculus]] required)<br />
|<math>\pi \int_a^b \left({\left[R_O(x)\right]}^2 - {\left[R_I(x)\right]}^2\right) \mathrm{d}x</math> <br />
|<math>R_O</math> and <math>R_I</math> are functions expressing the outer and inner radii of the function, respectively.<br />
|}<br />
<br />
===Volume ratios for a cone, sphere and cylinder of the same radius and height===<br />
<br />
[[File:Inscribed cone sphere cylinder.svg|thumb|350px|A cone, sphere and cylinder of radius ''r'' and height ''h'']]<br />
The above formulas can be used to show that the volumes of a [[cone (geometry)|cone]], sphere and [[cylinder (geometry)|cylinder]] of the same radius and height are in the ratio '''1&nbsp;:&nbsp;2&nbsp;:&nbsp;3''', as follows.<br />
<br />
Let the radius be ''r'' and the height be ''h'' (which is 2''r'' for the sphere), then the volume of cone is<br />
<br />
:<math>\tfrac{1}{3} \pi r^2 h = \tfrac{1}{3} \pi r^2 (2r) = (\tfrac{2}{3} \pi r^3) \times 1,</math><br />
<br />
the volume of the sphere is<br />
<br />
:<math>\tfrac{4}{3} \pi r^3 = (\tfrac{2}{3} \pi r^3) \times 2,</math><br />
<br />
while the volume of the cylinder is<br />
<br />
:<math>\pi r^2 h = \pi r^2 (2r) = (\tfrac{2}{3} \pi r^3) \times 3.</math><br />
<br />
The discovery of the '''2&nbsp;:&nbsp;3''' ratio of the volumes of the sphere and cylinder is credited to [[Archimedes]].<ref>{{cite web |first=Chris |last=Rorres|url = http://www.math.nyu.edu/~crorres/Archimedes/Tomb/Cicero.html|title = Tomb of Archimedes: Sources|publisher = Courant Institute of Mathematical Sciences|accessdate = 2007-01-02}}</ref><br />
<br />
== Volume formula derivations ==<br />
<br />
=== Sphere ===<br />
<br />
The volume of a [[sphere]] is the [[integral]] of an infinite number of infinitesimally small circular [[Disk (mathematics)|disk]]s of thickness ''dx''.<br />
The calculation for the volume of a sphere with center 0 and radius ''r'' is as follows.<br />
<br />
The surface area of the circular disk is <math>\pi r^2 </math>.<br />
<br />
The radius of the circular disks, defined such that the x-axis cuts perpendicularly through them, is<br />
<br />
<math>y = \sqrt{r^2-x^2}</math><br />
<br />
or<br />
<br />
<math>z = \sqrt{r^2-x^2}</math><br />
<br />
where y or z can be taken to represent the radius of a disk at a particular x value.<br />
<br />
Using y as the disk radius, the volume of the sphere can be calculated as <math> \int_{-r}^r \pi y^2 \,dx = \int_{-r}^r \pi(r^2 - x^2) \,dx.</math><br />
<br />
Now <math>\int_{-r}^r \pi r^2\,dx - \int_{-r}^r \pi x^2\,dx = \pi (r^3 + r^3) - \frac{\pi}{3}(r^3 + r^3) = 2\pi r^3 - \frac{2\pi r^3}{3}.</math><br />
<br />
Combining yields <math>V = \frac{4}{3}\pi r^3.</math><br />
<br />
This formula can be derived more quickly using the formula for the sphere's [[surface area]], which is <math>4\pi r^2</math>.<br />
The volume of the sphere consists of layers of infinitesimally thin spherical shells, and the sphere volume is equal to<br />
<br />
<math> \int_0^r 4\pi u^2 \,du</math> = <math> \frac{4}{3}\pi r^3.</math><br />
<br />
=== Cone ===<br />
The cone is a type of pyramidal shape. The fundamental equation for pyramids, one-third times base times altitude, applies to cones as well.<br />
<br />
However, using calculus, the volume of a [[Cone (geometry)|cone]] is the [[integral]] of an infinite number of infinitesimally thin circular [[Disk (mathematics)|disk]]s of thickness ''dx''.<br />
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.<br />
<br />
The radius of each circular disk is ''r'' if ''x'' = 0 and 0 if ''x'' = ''h'', and varying linearly in between—that is, <math>r\frac{(h-x)}{h}.</math><br />
<br />
The surface area of the circular disk is then <math> \pi \left(r\frac{(h-x)}{h}\right)^2 = \pi r^2\frac{(h-x)^2}{h^2}. </math><br />
<br />
The volume of the cone can then be calculated as <math> \int_{0}^h \pi r^2\frac{(h-x)^2}{h^2} dx, </math><br />
<br />
and after extraction of the constants: <math>\frac{\pi r^2}{h^2} \int_{0}^h (h-x)^2 dx</math><br />
<br />
Integrating gives us <math>\frac{\pi r^2}{h^2}\left(\frac{h^3}{3}\right) = \frac{1}{3}\pi r^2 h.</math><br />
<br />
== Volume in differential geometry ==<br />
{{main|volume form}}<br />
<br />
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 on a manifold|density]]. Integrating the volume form gives the volume of the manifold according to that form.<br />
<br />
Any [[orientation (mathematics)|oriented]] [[Riemannian manifold|Riemannian]] (or [[pseudo-Riemannian manifold|pseudo-Riemannian]]) [[manifold]] has a natural volume (or pseudo volume) form. In [[local coordinates]], it can be expressed as<br />
:<math>\omega = \sqrt{|g|} dx^1\wedge \dots \wedge dx^n</math><br />
where the <math>dx^i</math> are the [[1-form]]s providing an oriented basis for the [[cotangent bundle]] of the ''n''-dimensional manifold. Here, <math>|g|</math> is the absolute value of the [[determinant]] of the matrix representation of the [[metric tensor]] on the manifold.<br />
<br />
== Volume in thermodynamics ==<br />
{{Main| Volume (thermodynamics)}}<br />
<br />
In [[thermodynamics]], the '''volume''' of a [[thermodynamic system|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 [[thermodynamic temperature|temperature]]. For example, volume is related to the [[pressure]] and [[thermodynamic temperature|temperature]] of an [[ideal gas]] by the [[ideal gas law]].<br />
<br />
== See also ==<br />
{{cmn|3|<br />
* [[Area]]<br />
* [[Banach–Tarski paradox]]<br />
* [[Conversion of units#Volume|Conversion of units]]<br />
* [[Dimensional weight]]<br />
* [[Dimensioning]]<br />
* [[Length]]<br />
* [[Mass]]<br />
* [[Measure (mathematics)|Measure]]<br />
* [[Orders of magnitude (volume)]]<br />
* [[Perimeter]]<br />
* [[Volume form]]<br />
* [[Volume (thermodynamics)]]<br />
* [[Weight]]<br />
* [[Volumography]]<br />
}}<br />
<br />
==References==<br />
{{reflist}}<br />
<br />
==External links==<br />
{{Wikibooks|Geometry|Chapter 8|Perimeters, Areas, Volumes}}<br />
{{wikibooks|Calculus|Volume}}<br />
<br />
[[Category:Volume|*]]</div>DVdm