From Wikipedia, the free encyclopedia
A sphere of radius r has surface area 4πr2.
The surface area of a solid object is a measure of the total area that the surface of the object occupies.[1] The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc length of one-dimensional curves, or of the surface area for polyhedra (i.e., objects with flat polygonal faces), for which the surface area is the sum of the areas of its faces. Smooth surfaces, such as a sphere, are assigned surface area using their representation as parametric surfaces. This definition of surface area is based on methods of infinitesimal calculus and involves partial derivatives and double integration.
A general definition of surface area was sought by Henri Lebesgue and Hermann Minkowski at the turn of the twentieth century. Their work led to the development of geometric measure theory, which studies various notions of surface area for irregular objects of any dimension. An important example is the Minkowski content of a surface.
Definition[edit]
While the areas of many simple surfaces have been known since antiquity, a rigorous mathematical definition of area requires a great deal of care.
This should provide a function
which assigns a positive real number to a certain class of surfaces that satisfies several natural requirements. The most fundamental property of the surface area is its additivity: the area of the whole is the sum of the areas of the parts. More rigorously, if a surface S is a union of finitely many pieces S1, …, Sr which do not overlap except at their boundaries, then
Surface areas of flat polygonal shapes must agree with their geometrically defined area. Since surface area is a geometric notion, areas of congruent surfaces must be the same and the area must depend only on the shape of the surface, but not on its position and orientation in space. This means that surface area is invariant under the group of Euclidean motions. These properties uniquely characterize surface area for a wide class of geometric surfaces called piecewise smooth. Such surfaces consist of finitely many pieces that can be represented in the parametric form
with a continuously differentiable function The area of an individual piece is defined by the formula
Thus the area of SD is obtained by integrating the length of the normal vector to the surface over the appropriate region D in the parametric uv plane. The area of the whole surface is then obtained by adding together the areas of the pieces, using additivity of surface area. The main formula can be specialized to different classes of surfaces, giving, in particular, formulas for areas of graphs z = f(x,y) and surfaces of revolution.
Schwarz lantern with axial slices and radial vertices. The limit of the area as and tend to infinity doesn’t converge. In particular it doesn’t converge to the area of the cylinder.
One of the subtleties of surface area, as compared to arc length of curves, is that surface area cannot be defined simply as the limit of areas of polyhedral shapes approximating a given smooth surface. It was demonstrated by Hermann Schwarz that already for the cylinder, different choices of approximating flat surfaces can lead to different limiting values of the area; this example is known as the Schwarz lantern.[2][3]
Various approaches to a general definition of surface area were developed in the late nineteenth and the early twentieth century by Henri Lebesgue and Hermann Minkowski. While for piecewise smooth surfaces there is a unique natural notion of surface area, if a surface is very irregular, or rough, then it may not be possible to assign an area to it at all. A typical example is given by a surface with spikes spread throughout in a dense fashion. Many surfaces of this type occur in the study of fractals. Extensions of the notion of area which partially fulfill its function and may be defined even for very badly irregular surfaces are studied in geometric measure theory. A specific example of such an extension is the Minkowski content of the surface.
Common formulas[edit]
Shape | Equation | Variables |
---|---|---|
Cube | a = side length | |
Cuboid | l = length, b = breadth, h = height | |
Triangular prism | b = base length of triangle, h = height of triangle, l = distance between triangular bases, p, q, r = sides of triangle | |
All prisms | B = the area of one base, P = the perimeter of one base, h = height | |
Sphere | r = radius of sphere, d = diameter | |
Hemisphere | r = radius of the hemisphere | |
Hemispherical shell | R = external radius of hemisphere, r = internal radius of hemisphere | |
Spherical lune | r = radius of sphere, θ = dihedral angle | |
Torus | r = minor radius (radius of the tube), R = major radius (distance from center of tube to center of torus) | |
Closed cylinder | r = radius of the circular base, h = height of the cylinder | |
Cylindrical annulus | R = External radius
r = Internal radius, h = height |
|
Capsule | r = radius of the hemispheres and cylinder, h = height of the cylinder | |
Curved surface area of a cone |
s = slant height of the cone, r = radius of the circular base, h = height of the cone |
|
Full surface area of a cone | s = slant height of the cone, r = radius of the circular base, h = height of the cone | |
Regular Pyramid | B = area of base, P = perimeter of base, s = slant height | |
Square pyramid | b = base length, s = slant height, h = vertical height | |
Rectangular pyramid | l = length, b = breadth, h = height | |
Tetrahedron | a = side length | |
Surface of revolution | ||
Parametric surface | = parametric vector equation of surface,
= partial derivative of with respect to , |
Ratio of surface areas of a sphere and cylinder of the same radius and height[edit]
A cone, sphere and cylinder of radius r and height h.
The below given formulas can be used to show that the surface area of a sphere and cylinder of the same radius and height are in the ratio 2 : 3, as follows.
Let the radius be r and the height be h (which is 2r for the sphere).
The discovery of this ratio is credited to Archimedes.[4]
In chemistry[edit]
Surface area of particles of different sizes.
Surface area is important in chemical kinetics. Increasing the surface area of a substance generally increases the rate of a chemical reaction. For example, iron in a fine powder will combust, while in solid blocks it is stable enough to use in structures. For different applications a minimal or maximal surface area may be desired.
In biology[edit]
The surface area of an organism is important in several considerations, such as regulation of body temperature and digestion. Animals use their teeth to grind food down into smaller particles, increasing the surface area available for digestion. The epithelial tissue lining the digestive tract contains microvilli, greatly increasing the area available for absorption. Elephants have large ears, allowing them to regulate their own body temperature. In other instances, animals will need to minimize surface area; for example, people will fold their arms over their chest when cold to minimize heat loss.
The surface area to volume ratio (SA:V) of a cell imposes upper limits on size, as the volume increases much faster than does the surface area, thus limiting the rate at which substances diffuse from the interior across the cell membrane to interstitial spaces or to other cells. Indeed, representing a cell as an idealized sphere of radius r, the volume and surface area are, respectively, V = (4/3)πr3 and SA = 4πr2. The resulting surface area to volume ratio is therefore 3/r. Thus, if a cell has a radius of 1 μm, the SA:V ratio is 3; whereas if the radius of the cell is instead 10 μm, then the SA:V ratio becomes 0.3. With a cell radius of 100, SA:V ratio is 0.03. Thus, the surface area falls off steeply with increasing volume.
See also[edit]
- Perimeter length
- Projected area
- BET theory, technique for the measurement of the specific surface area of materials
- Spherical area
- Surface integral
References[edit]
- ^ Weisstein, Eric W. «Surface Area». MathWorld.
- ^ «Schwarz’s Paradox» (PDF). Archived (PDF) from the original on 4 March 2016. Retrieved 21 March 2017.
- ^ «Archived copy» (PDF). Archived from the original (PDF) on 15 December 2011. Retrieved 24 July 2012.
{{cite web}}
: CS1 maint: archived copy as title (link) - ^ Rorres, Chris. «Tomb of Archimedes: Sources». Courant Institute of Mathematical Sciences. Archived from the original on 9 December 2006. Retrieved 2 January 2007.
- Yu.D. Burago; V.A. Zalgaller; L.D. Kudryavtsev (2001) [1994], «Area», Encyclopedia of Mathematics, EMS Press
External links[edit]
- Surface Area Video at Thinkwell
The surface area of a three-dimensional object is the total area of all its faces. In real-life we use the concept of surface areas of different objects when we want to wrap something, paint something, and eventually while building things to get the best possible design. Let us learn all about the surface area of 3D shapes in this article.
1. | What is Surface Area? |
2. | Surface Area Formulas |
3. | Types of Surface Areas |
4. | Surface Area of Prism |
5. | FAQs on Surface Area |
What is Surface Area?
The total area occupied by the surfaces of an object is called its surface area. In geometry, different 3D shapes have different surface areas which can be easily calculated using the formulas that we will be learning in this article. The surface area is classified into two categories:
- Lateral surface area or Curved surface area
- Total surface area
Let us learn about the general surface area formulas of various shapes.
Surface Area Formulas
There is a different surface area formula for every geometrical shape, but the idea behind all is to get the total area occupied by all the faces of the objects. In this section, we will learn about the various formulas used to calculate the surface area of different objects. The total surface area considers all the faces of the 3D shape including the flat surfaces and the curved surfaces, while the lateral surface area is calculated to find the area occupied by the curved surface of the shape. It does not include the area of the bases. A sphere is one 3D figure which has only one round surface with no flat base.
Observe the table given below to learn the surface area formulas of different 3D shapes.
3D Shape | Total Surface Area (TSA) | Lateral Surface Area (LSA)/Curved Surface Area |
---|---|---|
Cube | 6a2 | 4a2, where a is the length of each side |
Cuboid | 2 (lw + wh + lh) | 2h (l + w), where l, w, and h are the length, width, and height of the cuboid |
Cone | πr(r + l) | πrl, where r is the radius and l is the slant height of the cone |
Cylinder | 2πr(r + h) | 2πrh, where r is the radius and h is the height of the cylinder |
Sphere | 4πr2, where r is the radius of the sphere | Not applicable |
Types of Surface Areas
As we have already discussed that there are two types of surface areas for three-dimensional shapes: total surface area and curved/lateral surface area. The total surface area includes the area of all the faces of the shape while the curved or lateral area includes only the area of the side faces of the shapes. Observe the cylinder given below to understand the difference between total surface area and curved surface area.
Surface Area of Prism
A prism is a 3D solid object made up of two congruent bases which are polygons and congruent lateral faces which are rectangular in shape. There are two types of areas that a prism has — the lateral surface area and the total surface area. The lateral area of a prism is the sum of the areas of all its lateral faces whereas the total surface area of a prism is the sum of its lateral area and area of its bases.
The lateral surface area of prism = base perimeter × height
The total surface area of a prism = Lateral surface area of prism + area of the two bases = (2 × Base Area) + Lateral surface area = (2 × Base Area) + (Base perimeter × height).
There are seven types of prisms based on the shape of the bases of prisms. The bases of different types of prisms are different so are the formulas to determine the surface area of the prism. Observe the table given below to understand this concept behind the surface area of various prisms:
Shape | Base | Surface Area of Prism = (2 × Base Area) + (Base perimeter × height) |
---|---|---|
Triangular Prism | Triangle | Surface area of triangular prism = bh + (s1 + s2 + b)H |
Square Prism | Square | Surface area of square prism = 2a2 + 4ah |
Rectangular Prism | Rectangle | Surface area of rectangular prism = 2(lw + wh + lh) |
Trapezoidal Prism | Trapezoid | Surface area of trapezoidal prism = h (b + d) + l (a + b + c + d) |
Pentagonal Prism | Pentagon | Surface area of pentagonal prism = 5ab + 5bh |
Hexagonal Prism | Hexagon | Surface area of hexagonal prism = 6ah + 3√3a2 |
Octagonal Prism | Octagon | Surface area of octagonal prism = 4a2 (1 + √2) + 8aH |
☛ Related Articles
- Surface Area of Cube
- Surface Area of Cuboid
- Surface Area of Cone
- Surface Area of Sphere
- Surface Area of a Hemisphere
- Surface Area of Cylinder
- Surface Area of Pyramid
- Difference Between Area and Surface Area
FAQs on Surface Area
What is the Definition of Surface Area?
The surface area is the total area covered by all the faces of a 3D object. For example, if we need to find the quantity of paint required to paint a cube, then the surface on which the paint will be applied is its surface area. It is always measured in square units.
What is the Formula for Surface Area?
The formula to find the surface areas of different geometrical shapes is to add the areas of each of their faces. It can be very tedious to find the area of each face individually, so we have surface area formulas for each of the geometrical figures. Some of the formulas are listed below:
- Total surface area of a cube = 6 × (side)2
- Surface area of sphere = 4πr2
- Total surface area of cone = πr(r + l)
Is Surface Area the Same as Area?
The main difference between surface area and area is that surface area is the area of 3D shapes such as a sphere, cylinder, and so on, whereas, area is the measurement of the space occupied by 2D shapes such as triangles, squares, and so on.
How to Find the Surface Area of a Rectangular Prism?
The surface area of a rectangular prism can be calculated by using the following formula: Surface area of rectangular prism = 2(lw + wh + lh), where l, w, and h are the length, width, and height of the rectangular prism respectively.
What is the Surface Area of a Cube?
A cube is made up of 6 square faces. So, the surface area of a cube is the sum of the areas of all those 6 faces. We know that area of a square = a2, where a is the side length of the square. So, the surface area of a cube with side length a is 6a2.
What is the Surface Area of a Circle?
The surface area of a circle is the total area covered by the boundary of a circle. The area of a circle with radius ‘r’ is, Area of a circle = πr2.
What is the Surface Area of a Cone?
The area occupied by a cone is referred to as the surface area of a cone. The total surface area of a cone is, T = πr(r + l), and the curved surface area of a cone, S = πrl. Here ‘r’ is the radius of the base and ‘l’ is the slant height of the cone.
What is the Surface Area of a Cylinder?
The surface area of a cylinder is the total region covered by the surface of the cylindrical shape. The total surface area of a cylinder is given as the sum of lateral surface area and the area of two bases. It is mathematically expressed as 2πr(r + h) and is expressed in square units, like m2, in2, cm2, yd2, etc. The curved or the lateral surface area of a cylinder is calculated with the formula, Curved surface area = 2πrh.
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Англо-русский строительный словарь. — М.: Русский Язык.
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Англо-русский строительный словарь.
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Англо-русский словарь нормативно-технической терминологии > surface area
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SA, surface area
морской район; площадь поверхности
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SURFA, surface area
морской район; площадь поверхности
English-Russian dictionary of planing, cross-planing and slotting machines > surface area
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English-Russian big medical dictionary > surface area
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English-Russian dictionary on nuclear energy > surface area
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1) площадь поверхности
2) поверхность
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Англо-русский словарь нефтегазовой промышленности > surface area
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9) Авиационная медицина: площадь поверхности , участок поверхности
10) Макаров: площадь полной поверхности
Универсальный англо-русский словарь > surface area
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Англо-русский универсальный дополнительный практический переводческий словарь И. Мостицкого > surface area
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English-russian automobile dictionary > surface area
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площадь поверхности, удельная поверхность.
English-Russian dictionary of terms for geological exploration drilling > surface area
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English-Russian dictionary of terminology cable technology > surface area
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English-Russian dictionary of computer science and programming > surface area
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Англо-русский словарь по ядерным испытаниям и горному делу > surface area
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Англо-русский словарь по авиационной медицине > surface area
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English-Russian military dictionary > surface area
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См. также в других словарях:
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Surface area — is the measure of how much exposed area an object has. It is expressed in square units. If an object has flat faces, its surface area can be calculated by adding together the areas of its faces. Even objects with smooth surfaces, such as spheres … Wikipedia
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surface area — surface ,area noun count the total area of a surface or surfaces, especially the outside surfaces of an object: enough paint to cover a surface area of 900 square feet … Usage of the words and phrases in modern English
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surface area — surface .area n the area of the outside of an object that can be measured … Dictionary of contemporary English
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surface area — noun the extent of a 2 dimensional surface enclosed within a boundary (Freq. 2) the area of a rectangle it was about 500 square feet in area • Syn: ↑area, ↑expanse • Derivationally related forms: ↑areal ( … Useful english dictionary
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surface area — UK / US noun [countable] Word forms surface area : singular surface area plural surface areas maths the total area of a surface or surfaces, especially the outside surfaces of an object enough paint to cover a surface area of 900 square feet … English dictionary
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surface area — paviršiaus plotas statusas T sritis Standartizacija ir metrologija apibrėžtis Nagrinėjamojo paviršiaus plotas. atitikmenys: angl. surface area vok. Oberflächeninhalt, m rus. площадь поверхности, f pranc. aire de surface, f … Penkiakalbis aiškinamasis metrologijos terminų žodynas
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surface area — paviršiaus plotas statusas T sritis fizika atitikmenys: angl. surface area vok. Oberflächeninhalt, m rus. площадь поверхности, f pranc. aire de surface, f … Fizikos terminų žodynas
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surface pressure-surface area isotherm — Surface Pressure Surface Area Isotherm Изотерма поверхностное давление площадь Зависимость поверхностного давления монослоя Ленгмюра на поверхности водной субфазы от площади, занимаемой молекулами поверхностно активного вещества в этом… … Толковый англо-русский словарь по нанотехнологии. — М.
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Surface area to volume ratio — In chemical reactions involving a solid material, the surface area to volume ratio is an important factor for the reactivity, that is, the rate at which the chemical reaction will proceed. In some industries it is abbreviated sa/vol.Physical… … Wikipedia
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Surface area, volume, and average depth of oceans and seas — ▪ Table Surface area, volume, and average depth of oceans and seas area volume average depth 000,000 sq km 000,000 sq mi 000,000 cu km 000,000 cu mi m ft Atlantic Ocean without marginal seas 82.440 31.830 324.600 77.900 3,930 12,890 with… … Universalium
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surface area — noun The total area on the surface of a three dimensional figure … Wiktionary
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With wok cooking, you chop things up into little pieces for maximum surface area, so they can cook in minutes, if not seconds. Sauteing is energy efficient; baking is not.
Jennifer Lee
PRONUNCIATION OF SURFACE AREA
GRAMMATICAL CATEGORY OF SURFACE AREA
Surface area is a noun.
A noun is a type of word the meaning of which determines reality. Nouns provide the names for all things: people, objects, sensations, feelings, etc.
WHAT DOES SURFACE AREA MEAN IN ENGLISH?
Surface area
The surface area of a solid object is the total area of the object’s faces and curved surfaces. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc length of one-dimensional curves, or of the surface area for polyhedra, for which the surface area is the sum of the areas of its faces. Smooth surfaces, such as a sphere, are assigned surface area using their representation as parametric surfaces. This definition of surface area is based on methods of infinitesimal calculus and involves partial derivatives and double integration. A general definition of surface area was sought by Henri Lebesgue and Hermann Minkowski at the turn of the twentieth century. Their work led to the development of geometric measure theory, which studies various notions of surface area for irregular objects of any dimension. An important example is the Minkowski content of a surface.
Definition of surface area in the English dictionary
The definition of surface area in the dictionary is the total area on the surface of a three-dimensional figure.
WORDS THAT RHYME WITH SURFACE AREA
Synonyms and antonyms of surface area in the English dictionary of synonyms
Translation of «surface area» into 25 languages
TRANSLATION OF SURFACE AREA
Find out the translation of surface area to 25 languages with our English multilingual translator.
The translations of surface area from English to other languages presented in this section have been obtained through automatic statistical translation; where the essential translation unit is the word «surface area» in English.
Translator English — Chinese
面积
1,325 millions of speakers
Translator English — Spanish
área de superficie
570 millions of speakers
Translator English — Hindi
सतह क्षेत्र
380 millions of speakers
Translator English — Arabic
مساحة السطح
280 millions of speakers
Translator English — Russian
площадь поверхности
278 millions of speakers
Translator English — Portuguese
área de superfície
270 millions of speakers
Translator English — Bengali
ভূপৃষ্ঠের
260 millions of speakers
Translator English — French
surface
220 millions of speakers
Translator English — Malay
kawasan permukaan
190 millions of speakers
Translator English — German
Oberfläche
180 millions of speakers
Translator English — Japanese
表面積
130 millions of speakers
Translator English — Korean
표면적
85 millions of speakers
Translator English — Javanese
Wilayah lumahing
85 millions of speakers
Translator English — Vietnamese
diện tích bề mặt
80 millions of speakers
Translator English — Tamil
மேற்பரப்பு
75 millions of speakers
Translator English — Marathi
पृष्ठभागाचे क्षेत्रफळ
75 millions of speakers
Translator English — Turkish
yüzey alanı
70 millions of speakers
Translator English — Italian
superficie
65 millions of speakers
Translator English — Polish
Powierzchnia
50 millions of speakers
Translator English — Ukrainian
Площа поверхні
40 millions of speakers
Translator English — Romanian
suprafață
30 millions of speakers
Translator English — Greek
επιφάνεια
15 millions of speakers
Translator English — Afrikaans
oppervlakte
14 millions of speakers
Translator English — Swedish
ytarea
10 millions of speakers
Translator English — Norwegian
flateareal
5 millions of speakers
Trends of use of surface area
TENDENCIES OF USE OF THE TERM «SURFACE AREA»
The term «surface area» is very widely used and occupies the 21.175 position in our list of most widely used terms in the English dictionary.
FREQUENCY
Very widely used
The map shown above gives the frequency of use of the term «surface area» in the different countries.
Principal search tendencies and common uses of surface area
List of principal searches undertaken by users to access our English online dictionary and most widely used expressions with the word «surface area».
FREQUENCY OF USE OF THE TERM «SURFACE AREA» OVER TIME
The graph expresses the annual evolution of the frequency of use of the word «surface area» during the past 500 years. Its implementation is based on analysing how often the term «surface area» appears in digitalised printed sources in English between the year 1500 and the present day.
Examples of use in the English literature, quotes and news about surface area
QUOTES WITH «SURFACE AREA»
Famous quotes and sentences with the word surface area.
With wok cooking, you chop things up into little pieces for maximum surface area, so they can cook in minutes, if not seconds. Sauteing is energy efficient; baking is not.
10 ENGLISH BOOKS RELATING TO «SURFACE AREA»
Discover the use of surface area in the following bibliographical selection. Books relating to surface area and brief extracts from same to provide context of its use in English literature.
1
Powder Surface Area and Porosity
An introduction to experimental methods used to study the surface area, porosity, density, and particle size of powders encountered in industry, for readers with little previous knowledge of solid surfaces but who, for example, just …
Seymour Lowell, Joan E. Shields, 1991
2
Adsorption, surface area, and porosity
The principal aim of the second edition of this book remains the same as that of the first edition: to give a critical exposition of the use of the adsorption methods for the assessment of the surface and pore size distribution of finely …
Sidney John Gregg, K. S. W. Sing, 1991
3
Characterization of Porous Solids and Powders: Surface Area, …
The growth of interest in newly developed porous materials has prompted the writing of this book for those who have the need to make meaningful measurements without the benefit of years of experience.
4
Surface Area and Porosity Determinations by Physisorption: …
Surface Area and Porosity Determinations by Physisorption is a practical guide for industry or academics to the measurement of surface area and pore size using the tool of physical adsorption.
5
The Growth of the Surface Area of the Human Body
This work provides an extensive analysis of one of the major body measures, surface area. It is strictly experimental and descriptive; numerical and graphic methods are used to present major findings.
Id). From the large body of information provided by electron micrographs, it has
been established that the majority of the clay minerals found in soils are platelike
or disk shaped. 1.1.6 Surface Area of Soil Particles Relationship to Particle Size …
William A. Jury, Robert Horton, 2004
TABLE 5.2 Comparison of Agar Cubes Cube Dimension Surface Area (cm2)
Volume (cm>) Surface Area: Volume (Simplest Form) 3 cm 2 cm 1 cm 3. Prepare
a data table like Table 5.2 and do the calculations necessary to complete it.
8
Wrappers Wanted: A Mathematical Adventure in Surface Area
Look no further! This unique tale takes the reader up to the North Pole and describes how Santa challenges his top elf, Snips Cleaver, to conserve paper because the North Pole is «going green.
Candice Yarbray Brucke, 2009
1.9 Surface area of particles Within the clay fraction there are particles small
enough to undergo erratic Brownian movement arising from bombardment by
water molecules in thermal motion. For this order of size, settling procedures are
…
T. J. Marshall, J. W. Holmes, C. W. Rose, 1996
He estimated the total ‘capillary’ surface area in an average man to be 6300
square metres. Intaglietta and Zweifach (1971) used an in-vivo technique to map
the vascular components of the rabbit’s mesentery and arrived at results that
appear …
10 NEWS ITEMS WHICH INCLUDE THE TERM «SURFACE AREA»
Find out what the national and international press are talking about and how the term surface area is used in the context of the following news items.
Surface of Pluto surprisingly young, say scientists
It is a well known fact that smaller objects cool faster than larger ones of the same shape because of their larger surface area. This principle also holds true for … «Youth Independent News, Jul 15»
Thick Cortex Could Be Key in Down Syndrome
Reductions in cortical surface area and increases in cortical thickness in brains of youth with Down Syndrome relative to typical controls. Panel (a) displays … «DrexelNow, Jun 15»
New ‘designer carbon’ from Stanford boosts battery performance
The activation process creates nanosized holes, or pores, that increase the surface area of the carbon, allowing it to catalyze more chemical reactions and store … «Stanford University News, May 15»
New Images Show Ceres is a Colorful Alien World
(Photo : NASA/JPL-Caltech/UCLA) Ceres has an estimated surface area of 2,850,000 km2. That’s just under seven times the total surface area of California state … «Nature World News, Apr 15»
Can money buy your kids a bigger brain?
«Money can buy better education, homes in areas further away from … Both income and education correlated with brain surface area, particularly in areas … «Sydney Morning Herald, Apr 15»
Nearly 81% of Great Lakes’ surface area covered with ice, for the …
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REFERENCE
« EDUCALINGO. Surface area [online]. Available <https://educalingo.com/en/dic-en/surface-area>. Apr 2023 ».
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Dimensionality
Surface area of three-dimensional solids refers to the measured area, in square units, of all the surfaces of objects like cubes, spheres, prisms and pyramids.
One-dimensional figures have only one dimension, one direction that can be measured. A line is one dimensional, since it has only length but no width or height.
Two-dimensional figures have two dimensions: width and length. All plane figures are two dimensional or 2D. Think of a square, circle, triangle or rectangle.
Three-dimensional figures have three dimensions: width, length, and height or depth. When dealing with 3D, we can use height or depth interchangeably, based on what is being measured.
We would use height to describe a skyscraper, but we probably would use depth to describe a hole in the ground. Three-dimensional solids include everyday objects like people, pets, houses, vehicles, cubes, cereal boxes, donuts, planets, shoe boxes, and mathematics textbooks. We live in a 3D world.
Defining our terms
A 3D solid is a closed, three-dimensional shape. Examples of 3D solids are cubes, spheres, and pyramids.
A face of a 3D solid is a polygon bound by edges, which are the line segments formed where faces meet. Spheres have no faces.
A cube is a rectangular prism with six congruent, square faces.
A sphere is the set of all points in three dimensions that are equidistant from a given point. A hemisphere is one-half a sphere, its surface area including the circular cross section.
A prism is a 3D solid with two congruent, opposite faces (bases) with all other faces parallelograms of some sort. Examples of prisms are cubes and triangular, rectangular, hexagonal and octagonal prisms.
A right cylinder is a 3D solid with two circular, opposite faces (bases) and parallel sides connecting the circles. Any cross-section taken of a cylinder produces another circle congruent to the base.
A pyramid is a 3D solid with one polygon for a base (triangular, square, hexagonal — mathematically you have no limits) with all other faces being triangles. The Great Pyramid of Giza is a square pyramid.
A cone is a pyramid with a circular base. A cone has only one face, its base, and one vertex. It has height, h, the perpendicular measure from base to vertex, and slant height, l, which is the distance from base to vertex along its lateral surface.
Surface area formulas for prisms
For every 3D solid, we can examine each face or surface and calculate its surface area. Then, adding all the individual surface areas, we can find the surface area of the entire solid.
Think of it as unfolding the 3D shape like a cardboard box. Lay out every face, measure each, and add them. This is what occurs with geometry nets.
Formulas work for all the prisms. The faces of prisms will be recognizable polygons, so let’s review the area formulas for the basic polygons:
Try it!
Here is a triangular prism:
The area of each triangle is 12bhfrac{1}{2}bh:
Remember, though, we have two of these bases. Next, calculate the area of each of the three rectangular faces:
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9cm×25cm=225cm29cmtimes 25cm=225c{m}^{2}
Then, add all the individual areas to find the total surface area:
Square centimeters derive from the linear unit, centimeters. All surface areas of 3D solids are measured in square units, even when the objects are spheres, cylinders or cones.
Here is a rectangular prism:
What is it’s surface area?
Think: you need to measure three of the six faces, add them, and then multiply times 2, since the prism has three pairs of congruent faces. You must of course choose three dissimilar faces to capture length (l), width (w), and height (h):
Here is a cube representing all the gold that has ever been mined on earth:
What is its surface area? Think: a cube is six squares, each with a length equal to width equal to height. For a cube with any side b, the formula is:
Surface area formulas for non-prisms
For pyramids, the surface area formula for a pyramid with a base area, A, perimeter of base, p, and slant height, l, is:
If you are fortunate enough to have a square pyramid with a base length, b, and slant height, l, its formula is:
For spheres, calculate the surface area if you know the radius, r:
For hemispheres, you calculate the surface area as the sum of the base surface area, πr2pi {r}^{2}, plus the half sphere, 2πr22pi {r}^{2}, which gives:
For cones with slant height, l, and radius, r, surface area is calculated using this formula:
If you do not know the slant height but know height, h, and radius, r, you can calculate slant height, l, using the Pythagorean Theorem:
For cylinders with height, h, and radius, r, the formula for surface area is: