What is Surface: Definition and 1000 Discussions

A surface, as the term is most generally used, is the outermost or uppermost layer of a physical object or space. It is the portion or region of the object that can first be perceived by an observer using the senses of sight and touch, and is the portion with which other materials first interact. The surface of an object is more than "a mere geometric solid", but is "filled with, spread over by, or suffused with perceivable qualities such as color and warmth".The concept of surface has been abstracted and formalized in mathematics, specifically in geometry. Depending on the properties on which the emphasis is given, there are several non equivalent such formalizations, that are all called surface, sometimes with some qualifier, such as algebraic surface, smooth surface or fractal surface.
The concept of surface and its mathematical abstraction are both widely used in physics, engineering, computer graphics, and many other disciplines, primarily in representing the surfaces of physical objects. For example, in analyzing the aerodynamic properties of an airplane, the central consideration is the flow of air along its surface. The concept also raises certain philosophical questions—for example, how thick is the layer of atoms or molecules that can be considered part of the surface of an object (i.e., where does the "surface" end and the "interior" begin), and do objects really have a surface at all if, at the subatomic level, they never actually come in contact with other objects.

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  1. J

    Power of radiation received by a surface

    Homework Statement Homework EquationsThe Attempt at a Solution Using Stefan Boltzmann Law , The power emitted per unit area by the small sphere is P/A = eσT4 . The power absorbed per unit area by the surface is given as P/A = eσT04 . How should I use the distance between the two surfaces ?
  2. A

    Electroless nickel plating - surface preparation

    Hi, I am conducting the experiments with the electroless nickel plating of the brass (CZ121). I have read a lot of the literature about this process prior to the lab tests. All brass surface cleaning procedures that I have came across involve the electroless cleaning (I understand why)...
  3. M

    A How Does Surface Energy Affect Thin Fluid Films?

    I'm studying thin fluid films, and the text writes free surface energy of a film (puddle) over domain ##(0,X)## can be expressed as $$E=\int_0^X \left[\frac{h_x^2}{2}+\omega(h)+G\frac{h^2}{2} \right]\, dx$$ where ##X## is a length that the thin film (puddle) rests on, ##h## is the height of the...
  4. Y

    Why do charges outside surface create no net flux?

    Why do charges outside the surface contribute 0 net flux? The book I'm reading says it's because the flux entering the surface cancels out with the flux exiting the surface. But that means E dot Area must be exactly the same magnitude when entering and exiting to cancel out. But we know E-field...
  5. T

    Surface Charge density of glass cyclinder

    Homework Statement Consider an infinitely long one dimensional conducting wire with a homeogenous charge density ##\lambda##, running along the central axis of an infinitely long cyclindrical glass casing of radius b (glass is a dielectric material). Calculate: a) The displacement vector...
  6. J

    Surface bound charge on the outer surface of a dielectric

    Homework Statement With regards to a one dimensional conducting wire with a homogeneous charge density λ surrounded by a cylindrical glass dielectric of radius R, find: (a). The displacement vector inside the dielectric (b). The surface bound charges on the surface of the dielectric Sorry...
  7. J

    I Evaporation under vacuum; surface area

    I run a vacuum distillation unit that is used to distill ethylene glycol. The old glycol is subjected to 25Hg of vacuum at a temp of 275 degrees F. There are burner tubes submerged in the glycol to heat it up. The vessel has a diameter of 36 inches and is 124 inches long. We fill the vessel...
  8. M

    Literature survey - wing surface roughness effect on performance

    Homework Statement I am currently trying to do a literature survey on my project task 'effect of wing surface roughness on wing performance'. I have been struggling to find many research papers that are of a similar experiment to mine, however i have come across many that investigate the effect...
  9. N

    How do i choose the Surface area vector in different cases?

    Homework Statement Suppose we have a Electic field, E (vector) = kr2r(vector). Find the total charge contained in the sphere of radius R centered in the origin. solution- here E can also be written as kr3r∧, where r∧ is the unit vector this is the given question , so obiously the best way to...
  10. Monsterboy

    Finding the surface RMS error using Zernike coefficients

    Hello, I am given 200,000 surface points in terms of x,y and z coordinates which is supposed to represent a circular paraboloid antenna reflector surface and another 200,000 points when the antenna surface is subjected to wind loads and gravity. I am supposed to find the surface RMS error of...
  11. M

    Kinetic Friction Between Block and Surface (HW Check)

    Homework Statement A 10 g bullet is fired at 200 m/s into a 1 kg block after which they slide together 2 m on a horizontal surface. Determine the coefficient of kinetic friction between the block and surface. Homework Equations ##M_AV_{Ai} + M_BV_{Bi} = 0## ##WNC = ΔE## The Attempt at a...
  12. P

    EMF between an axis and the surface of long wire

    A friend mine of gave me a problem : Calculate the Emf b/w the axis and surface of a long current carrying wire of radius ##r## and current density ##J##. I am not able to understand why there would be a potential difference between the axis and surface but i think that either of these could...
  13. A

    Negative Sensible Heat Flux at Earth's Surface

    I'm a bit confused as to how to imagine a negative sensible heat flux near the Earth's surface. Negative means that sensible heat is moving towards the surface. My book states that that would mainly occur at nighttime. During day there is a positive sensible heat flux and sensible heat moves...
  14. C

    I Surface Area of Volume of Revolution

    The problem is, find the surface area of the volume of revolution generated by rotating the curve y=e2x between x=0 and x=2 about the x-axis. Here's what I have so far... SA=∫y√(1+y2)dx =∫e2x√(1+4e4x)dx and from here I'm not really sure what to do. Any help would be appreciated.
  15. A

    B What exactly happens when touch a surface

    Hello, I'm accidentaly confused when my mate ask me "what actually happen when touch a surface of mass, ie: table, chair, etc). Which we are know that 99,999999999% of atom is space" Is we really touch atom? Help me please
  16. E

    MHB Proving an Infinite Number of Integer Points on a Level Surface

    Given is the function f: R2 -> R, with f(x,y)=x2+y2-6xy+8y. The level surface f(x,y)=1 contains infinitely much points (x,y) where x and y are integer. How can I prove this? I see that it is true with some examples, but how can I prove this. Do I need to use the gradient? Or tangent planes? Or...
  17. D

    Electric Flux through Cubical Surface Enclosing Sphere

    Homework Statement A uniform charge density of 700 nC/m3 is distributed throughout a spherical volume of radius 6.00 cm. Consider a cubical Gaussian surface with its center at the center of the sphere. [reference picture] What is the electric flux through this cubical surface if its edge...
  18. Kaneki123

    B A Question about Effect of Surface Area on Loudness

    Okay... I have a question about "effect of surface area on loudness".I am going to upload a diagram along this post.It shows two scenarios. The "red thing" is a barrier, which allows absolutely no air contact between the speaker and the listener. So the only way the sound can travel outside is...
  19. ORF

    How surface tension is measured for molten metals?

    Hello How the surface tension is measured for molten metals? I have heard about the sessile drop, but it seems to be a very inaccurate method... Thank you for your time. Regards.
  20. M

    B Surface volume of 3-sphere with radius of 2 Planck length?

    What is the surface area ("surface volume") of a 3-sphere having a radius of 2 Planck lengths? Is the product of the Planck's constant, Einstein's proportionality constant and Planck time also equal to this volume? Does this equivalence signify anything? What does it signify?
  21. L

    Cauchy Stress Components from Surface Force

    Hi, I've been trying to figure out how to get Cauchy Stress Tensor components (~9) from a surface force for a while now. My background in this subject is not too deep, but I'm trying to build a renderer simulation in my free time. I can get surface traction from a Stress Tensor: t =...
  22. A

    A What software and equipment do I need to view scanned surface data?

    Hello everyone, I just had a question for you all. I am trying to use a laser to scan a particular surface. What software or data retrieval tool would I need in order to view the surface in question after scanning it with a laser? Also, what wavelength and wattage would you suggest for getting...
  23. P

    When does gravity take over surface tension?

    I want to demonstrate to flat earthers that water does indeed stick to a ball. If we want to do a scale model of the earth, at which radius will gravity overcome the surface tension?
  24. C

    B Can a Subsea Lifting Bag With CO2 Rise to the Surface?

    This may sounds like a stupid question but... If you were to use a subsea lifting bag filled with O2 it would rise to the surface. Would the same happen with CO2? I assume the density of CO2 is different so the amount required would be more or less than O2, but it is still less dense than...
  25. L

    Surface area of a circular cylinder cut by a slanted plane

    Homework Statement Cylinder : x^2 + y^2 = 1 Plane that intersects above cylinder: y + z = 2 What is the surface area of the sides of this cylinder? Homework Equations dS= R1 d@ dz @ is from 0 to 2 pi z is from 0 to 2 - y dS=(Zx^2 + Zy^2 + 1)^.5 dA Where Z = 2 - yThe Attempt at a Solution I...
  26. A

    A Ball is rolling on a flat surface

    Let's say we have a rolling without slipping (e.g. mentioned ball) on flat surface. Does it mean that the ball will accelerate to infinity ?
  27. D

    I Finding a unit normal to a surface

    Hi. I'm trying to self-study vector calculus and I have to admit I struggle with it. As regards finding normals to a surface I know 2 ways - one involves writing the surface equation as f(x.y.z) = 0 and taking the gradient. The other method involves writing the surface in terms of 2 parameters...
  28. W

    How Does Specific Gravity Impact NPSH in Centrifugal Pumps?

    Head psa(suction surface pressure) = 2.31xP/specific gravity This is one of the factors to calc NPSH. Shows how much head is pushing liquid through the pump. What does the specific gravity have to do with surface pressure of a liquid before it goes into the pump? Isn't it just involving the...
  29. D

    Fluid temperature change over cold surface?

    For my research I am trying to study the temperature change of a warm fluid (air) flowing over a cold surface, but I have not studied fluid mechanics. Does anyone know of an equation that can be used to analyze this problem? To give some reference, the hot air is 49 Celsius and the cold air is...
  30. E

    Electric field outside conductor surface

    I'm confused as to how this expression E= (δ/εo) can't be used to calculate the electric field of a perfectly flat part of a surface even farther from just above the surface.If you just extend the same cylindrical Gaussian surface used for this proof, wouldn't the field stay the same no matter...
  31. B

    B GR Curvature at Light Cone Surface: Smooth, Bent, Blocked?

    For example, the curvature due to a mass; does that curvature continue passing from within to outside the mass's light cone? If so, is the mass subject to the external curvature? If not, does the curvature have a discontinuity at the light cone surface?
  32. K

    Finding Depth of Water Loss Using Surface Area

    Homework Statement A city with 30,000 residents lies next a lake which is their only source of water. The average family of four in this city uses 1100 liters of water per day. Neglecting rain and evaporation, how much depth would the lake lose per year if it covered 40 square kilometers...
  33. N

    Small sphere in a circular surface

    Homework Statement A small sphere of radius R held against the inner surface of a smooth spherical shell of radius 6R as shown in figure. The masses of the shell and small sphere are 4m and m respectively. This arrangement is placed on a smooth horizontal table. The small sphere is now...
  34. D

    A Determine the flux of the vector field trough the surface

    From my drawings it seems to be half of hemisphere. Am I right? How can I solve this task? Determine the flux of the vector field $$ f=(x,(z+y)e^x,-xz^2)^T$$ through the surface $Q(u,w)$, which is defined in the follwoing way: 1) the two boundaries are given by $$\delta...
  35. Q

    Relationship between line current & surface current density

    Homework Statement In a configuration having axial symmetry about the z axis, a line current I flows in the −z direction along the z axis. This current is returned at the radii a and b, where there are uniform surface current densities Kza and Kzb , respectively. The current density is zero in...
  36. O

    Energy Conservation: Puck on Wood on Frictionless Surface

    Homework Statement Hey all, another problem. There is a 1 meter wooden panel that is on a frictionless surface. A puck is placed on one end of the panel and is pushed towards the other side. The mass of the panel is 10 times that of the puck. Also, there is a friction coefficient of uk=0.15...
  37. Pushoam

    What shape does the surface of a rotating liquid take?

    Homework Statement Homework EquationsThe Attempt at a Solution If I consider an arc shaped element of the liquid, then the physical forces acting on it are 4 different tensions , normal force and gravitational force on it. Two of the tensions would be acting along tangential direction...
  38. A

    I Prove that solid angle of any closed surface is 4pi

    I googled a lot on proof of Gauss theorem and nearly every other proof (on web and so on books) state that solid angle of closed surface is 4pi but I can't find the proof of this nowhere ! I tried setting up the integral but don't know how to proceed furthur : Ω=∫(cosθ/r^2)*dA Also The one...
  39. J

    I Lambertian Surface: Exploring Radiant Intensity and Incident Angles

    Hello. I'm curious about the lambertian surface. Suppose in a given flat, surface of area A the light comes in, the incident angle being theta. The observer vector coincides with the light source, the angle between the normal of the surface being theta also. Then, when I calculate the radiant...
  40. terryds

    I Unit normal vector of a surface

    What is actually the unit normal vector of a surface? Is it this? Or this one? I see that those are opposite in direction. But, I want the correct one, which means that it should point outward. So, which one is correct?
  41. D

    A Wulff construction for surface energy dependent on depth

    Hello, Using surface energy dependence on surface orientation it is possible to predict equilibrium crystal shape by applying Wulff construction. But I faced the problem when the surface energy depends not only on the surface orientation but also on the surface depth or surface termination and...
  42. K

    Surface Tension of a soap film

    I don't understand, when calculating the force to change the surface area of the film, how the length obtained in the diagram below is "l" (lowercase L). I understand that there are two surfaces to overcome, hence the factor of 2, but why is the length perpedicular to the force used and not...
  43. Hiero

    How the surface area of a cone changes; special relativity

    Homework Statement A cone has half angle θ0 and lateral surface area S0 in the frame in which the cone is at rest. If someone moves at relative speed β=v/c along the cones symmetry axis, what surface area will they see for the cone? Homework Equations I believe the lateral surface area of a...
  44. K

    B Calculus of variation. Minimum surface

    so df/dy' is yy'/ √(1+y'^2) then we are supposed to do y' . [ yy'/ √(1+y'^2) ] - y√(1+y'^2) how does this bring equation 2 in the image ?
  45. A

    I Information for black hole region in surface surrounding it

    At one point I read there was the concern that a black hole could lose bits of information. Then a theory arose that showed that all the bits in a black hole were to be found on the surface of the black hole. Thus if there were let's say 1000 particles in a black hole each of which could be...
  46. C

    Surface density on isolated conductors in space

    Homework Statement There are n isolated condutoctors in space: Sum of charge of all conductors is positive. Show that surface density is postivie everywhere on at least one of conductors Homework Equations Using induction The Attempt at a Solution -It's clear that if we have one conductor...
  47. Monsterboy

    Elliptical paraboloid surface in matlab using F/D = 0.3

    Homework Statement To generate a elliptical paraboloid antenna surface in MATLAB using the given F/D ratio (= 0.3) F- focal length D- Diameter = 50 m Homework Equations ## \frac {F}{D} =\frac {1}{4tan(\theta/2)} ## ## F = \frac {D^2}{16H} ## H = height of the paraboloid Equation of a...
  48. F

    Surface Runoff - Explained and Debated

    Homework Statement In my book , i was told that when the drainage of surface is high then the surface runoff will be low . However , i don't think it's correct . Homework EquationsThe Attempt at a Solution Definiton : Runoff can be described as the part of the water cycle that flows over...
  49. G

    Current flow on the surface of a permeability bigger than 1

    Hi, Quick description of the problem at hand: spherical perfect conductor around the origin with radius a, spherical shell (with radius b) around it made of a material with given magnetic permeability bigger than 1. Uniform Magnetic field in the area. The solution I am looking at (which I won't...
  50. dovidu

    B Breaking a granite surface plate....

    ----------------Q 1--------------------- hello it's been two weeks to figure out how much force would it take to break a granite surface plate size of 1) 30x30x8 (cm) 2) 40x60x8 (cm) literally breaking it in half with a fulcrum underneath and two forces acting on the top i've posted a number...
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