Surface Definition and 1000 Threads

  1. A

    Calculating surface tension with the Capillary Equation

    Homework Statement Hello everyone, I am doing an experiment and I've hit a snag with my calculations. I am looking at how concentrations of soap affect surface tension in water. I am have been using the capillary equation and capillary tubes for my calculations. I have practiced this method for...
  2. R

    Average Pressure Radiation on Perfectly Absorbing Surface

    Homework Statement A light source radiates a sinusoidal electromagnetic wave uniformly in all directions. This wave exerts an average pressure p on a perfectly reflecting surface a distance R away from it. What average pressure (in terms of p) would this wave exert on a perfectly absorbing...
  3. D

    Bound surface charge on a linear dielectric half-cylinder

    Homework Statement Problem statement in attached photo. This is an ungraded assigned problem which I am using to study for an exam, so I don't need the whole solution just help with a couple of points I am confused about. One: Part d) is really important to how I will answer part b). If we can...
  4. Akash47

    Block at rest on an inclined surface

    Homework Statement Homework Equations Component of force,equilibrium of force. The Attempt at a Solution In the problem (ii),the friction force is ##Mgcosθμ##,the component of weight in the inclined surface is ##Mgsinθ## and the component of the applied force ##F## along the inclined surface...
  5. EelAnes

    What is the coefficient of drag on a flat surface?

    What is the coefficient of drag on a flat surface? Note: The body is in free fall The object has 2 wings planform (it's a paper helicopter), which is flat The object's wing spin in a circular motion (anti-clockwise) during free fall
  6. Q

    The minimum inclination of a surface

    I am an IT student and working on a project, an automated system. It's not for a physics class. I can't say exactly what the system can do. But it uses Arduino to dispense servings of grains on a given schedule. I am more of a programmer than a physicist, I am looking for help on this. 1...
  7. D

    I A surface integral over infinite space

    Hi. If a function f is normalizable ,ie f→0 as | x | → infinity or r→ infinity then I presume the following surface integral f dS over infinite space is zero ? But I thought about this again and it seems like a case of zero x infinity. The function is zero at the infinite surface but the area...
  8. A

    What do surface tension vectors mean in this quote?

    I was reading Fundamentals of Inket Printing and it said the following: "The surface tension in a liquid causes a force to act in the plane of the free surface perpendicularly to a free edge in that surface." Can someone explain to me what this means? What's the direction of the force? I have...
  9. Eric Bretschneider

    Emission of light from a surface

    I came across someone in the lighting industry who insists that because of Gauss's divergence theorem and Maxwell's Laws that when light is emitted from a surface that it is only emitted orthogonal to the surface. I have tried to point out numerous real world examples that contradict the...
  10. S

    Simulating shape of spinning water surface

    I would like to simulate a simplified version of this phenomenon: where I will assume that the viscosity is zero and the liquid can therefore swirl around "laminarly" forever according to some velocity profile that I specify. How can I calculate the shape of the surface, at least in this...
  11. nmsurobert

    I Why Is Jupiter's Surface Gravity Not as High as Expected?

    I just read a couple articles discussing the surface gravity of Saturn and Jupiter. I would expect the "surface" gravity of these planets to be much higher than that of Earth. I understand how the low densities of these planets has influence on that, but I thought mass was related to gravity in...
  12. shk

    Gravitational Potential Energy questions near the surface of a planet

    Homework Statement The change in gravitational potential energy of a mass m as it moves from the surface to a height h above the surface of a planet of mass M and radius R is given by: ΔPE= GMmh/R(R+h) a) show that when h is very small compared to R , this approximates to the more familiar...
  13. jonathanm111

    Vector Calculus, setting up surface area integral.

    The question goes like: find the SA of the portion S of the cone z^2 =x^2 +y^2 where z>=0 contained within the cylinder y^2+z^2<=49 this is my attempt using the formula for SA, I could switch to parametric eqns, but even then I'd have hard time setting up limits of integration.
  14. A

    How high does the ball rise on the non-slip surface?

    Homework Statement A solid ball with radius of 9.7 cm is released from the height of hs=88.1 cm on a non-slip surface. After reaching its lowest point the ball begins to rise again, on a frictionless surface. How high does the ball rise on that side? Express your answer in cm. Homework...
  15. G

    I Glass -- how to increase the surface area

    I need to increase the surface area of the glass which will be used in a solar still with the intention of keeping the glass as cool as possible. My first thought was bubble wrap because it's transparent and I thought it would not interfere with the light but then I remembered it is a good...
  16. M

    Mathematica Manipulating a Surface and Color Contours

    Hi PF! I'm trying to have color contours of a surface and then manipulate the surface. Using the sample code below, we see that if you step forward Mathematica plots the surface and then also the color contours. However, rather than stepping forward, if we play the video the color contours...
  17. J

    A For MOSCAP: why is surface potential constant after Vg = Vth

    Hi, I'm studying MOSCAP at university and there are 3 regions based on Vg. Accumulation Depletion Inversion For P substrate the surface potential increases as I increase the gate voltage (positive). The books say that at Vg = threshold voltage the surface potential is maximum. But why does it...
  18. T

    How to evaluate a surface integral with three points?

    Homework Statement Let G=x^2i+xyj+zk And let S be the surface with points connecting (0,0,0) , (1,1,0) and (2,2,2) Find ∬GdS. (over S) Homework EquationsThe Attempt at a Solution I parametrised the surface and found 0=2x-2y. I’m not sure if this is correct. And I’m also uncertain about...
  19. T

    Volume of a Parametrised Surface

    Homework Statement Let C be the parametrised surface given by Φ(t,θ)=(cosθ/cosht, sinθ/cosht,t−tanht), for 0≤t and 0≤θ<2π Let V be the region in R3 between the plane z = 0 and the surface C. Compute the volume of the region V .Homework EquationsThe Attempt at a Solution I thought I needed...
  20. ccdani

    Transmission of blue light through ceramics and surface roughness effects

    Hey :) I measured the transmission of blue visible light (350-550nm) through lithiumdisilicate ceramics with an ulbricht ball and an spectrometer. The light source was a led dental curing unit (bluephase style). The light guide was positioned direct on the ceramics. Now I wanted to test...
  21. E

    How to Determine Electric Flow Through a Square Surface Due to a Nearby Charge?

    Homework Statement determine the electric flow through a square surface of side 2l due to a load + Q located at a perpendicular distance l from the center of the plane I really don't know how to answer this question .i need help guys Thanks Homework EquationsThe Attempt at a Solution I ended...
  22. M

    Conceptual Question: Block on a wedge on a frictionless surface

    Homework Statement This is more of a conceptual question, but say a block was set on top of an inclined plane, which was set on top of a frictionless level surface. Would the inclined plane move? Why or why not Homework Equations None The Attempt at a Solution My thought...
  23. J

    Forces on a Block and Friction on a Surface

    Homework Statement A 2.5 kg block is initially at rest on a horizontal surface. A horizontal force of magnitude 5.8 N and a vertical force are then applied to the block. The coefficients of friction for the block and surface are μs = 0.43 and μk = 0.24. (a) Determine the magnitude of the...
  24. M

    Calculate the given surface integral [Mathematical physics]

    Homework Statement Calculate \int_{S} \vec{F} \cdot d\vec{S} where \vec{F} = z \hat{z} - \frac{x\hat{x} + y \hat{y} }{ x^2 + y^2 } And S is part of the Ellipsoid x^2 + y^2 + 2z^2 = 4 , z > 0 and the normal directed such that \vec{n} \cdot \hat{z} > 0 Homework Equations All the...
  25. K

    What is the thickness of the drop if its radius is r?

    1. A small drop of fat floats on the surface of a liquid whose surface tension is s. Surface fat tension at the air-fat interface is s1, at the fat-liquid interface is s2. Determine the thickness of the drop if its radius is r.2. ##F=\sigma l## ##\delta P=\sigma (\frac 1 R_1 + \frac 1...
  26. K

    Surface tension trivial problem

    1. The films of the two liquids are separated by a bar of length l. The coefficients of surface tension of liquids are equal to s1 and s2, respectively. What force acts on the bar on the liquid side?(It is a rectangular surface of 2 liquids separated by a bar of length l) 2. Force=(surface...
  27. R

    I Why does Mars have so much iron on it's surface?

    Earth also has iron rich deposits, I think generally they are thought to be remains of meteorites. Same is likely for Mars, but there is a lot more iron (and compounds) on the surface of Mars than there is on Earth. Are there substantial amounts of silicate rocks, as Earth has?
  28. K

    How Does the Cassie-Baxter Model Explain the Lotus Effect?

    1.The lotus effect refers to self-cleaning properties that are a result of ultrahydrophobicity as exhibited by the leaves of "lotus flower". Dirt particles are picked up by water droplets due to the micro- and nanoscopic architecture on the surface, which minimizes the droplet's adhesion to that...
  29. Raihan amin

    The shape of the surface of a soap film

    1. Two coaxial rings of radius R=10 cm are placed to a distance L from each other.There is a soap film connecting the two rings(that looks like a cylinder which have different radii with z coordinate. (The rings lie in xy plane)).Derive a differential equation describing the shape r(z) of the...
  30. mishima

    Surface of a Cylinder inside a Sphere

    Homework Statement This is a problem from Boas, Mathematical Methods of the Physical Sciences chapter 5, section 5, number 6. Find the area of the cylinder x^2+y^2-y=0 inside the sphere x^2+y^2+z^2=1. Homework Equations This section deals with projecting curved areas onto a coordinate plane...
  31. Gene Naden

    I Differential for surface of revolution

    O'Neill's Elementary Differential Geometry contains an argument for the following proposition: "Let C be a curve in a plane P and let A be a line that does not meet C. When this *profile curve* C is revolved around the axis A, it sweeps out a surface of revolution M." For simplicity, he...
  32. M

    MHB Change the form of equation of surface

    Hey! :o We consider the surface $S$ of the space $\mathbb{R}^3$ that is defined by the equation $2(x^2+y^2+z^2-xy-xz-yz)+3\sqrt{2}(x-z)=1$. I want to find (using symmetric matrices) an appropriate orthonormal system of coordinates $(x_1, y_1, z_1)$ for which the above equation has the form...
  33. P

    Free surface charges on concentric cylinders

    Homework Statement Consider an infinitely long cylindrical rod with radius a carrying a uniform charge density ##\rho##. The rod is surrounded by a co-axial cylindrical metal-sheet with radius b that is connected to ground. The volume between the sheet and the rod is filled with a dielectric...
  34. Jozefina Gramatikova

    Fractional uncertainty of g on the surface of the Sun

    Homework Statement Homework Equations The Attempt at a Solution it looks like I got too big numbers for the uncertainty
  35. bob012345

    I Gabriel's Horn, Inside vs. Outside Surface area

    Consider Gabriel's Horn, the mathematical object formed by a surface of revolution of the curve x= 1/x from x=1 to infinity. It is known that one can fill the horn with a volume of Pi cubic units of paint but it would take an infinite amount to paint the surface. I think they usually mean the...
  36. I

    B How to find the surface density for a given linear density

    Given a square with a linear mass density of: λ(x) = a * x (see image below where black is high density and white is low density) how would you deduce what the surface mass density is? I get confused for the following reason: To me it seems that the surface mass density should depend on x...
  37. H

    I Gauss' law applied on a four-dimensional surface

    in a 4D plane or on a four-dimensional surface can gauss law be used?
  38. Death eater

    Does an ideal fluid have zero surface tension?

    Does ideal fluid have zero surface tension? What does zero surface tension signify?
  39. bob012345

    I How to measure the surface area of an arbitrary 3D object

    I'm looking for an easy way to get the surface area of an arbitrary shaped 3D object. Getting the volume is easy by water displacement. What about area? Any neat tricks? We know different shapes can have the same volume and thus different surface areas so it's not a trivial problem. The purpose...
  40. digogalvao

    Slowly oscillating surface current on a solenoid

    Homework Statement From an original surface current ##\vec{K}=K\hat{\phi}## on a finite solenoid, I got ##\vec{B}=\mu_{0}Kf(z)\hat{k}##, for ##r<R##. Assuming that ##\vec{K}## now slowly oscillates in time such as: ##\vec{K(t)}=K_{0}\cos\left(\omega t\right)\hat{\phi}##, so that I still can use...
  41. S

    I What is the proof that the divergence is normal to the surface?

    If I am given a function f( x , y , z , ...) = C then the normal direction to it is simply the (unit vector of the) divergence of the function. How has this been proven?
  42. Dante Meira

    Move a mass on frictionless surface in a vacuum chamber

    How much energy is necessary to move one kilogram of mass horizontally for one meter on a perfectly frictionless surface inside a vacuum chamber? Assuming the initial velocity of the mass is zero, the mass is at rest.
  43. J

    I Which object will hit the surface of a planet first?

    If we have two objects A and B appear on the opposite sides of the equator of a planet like Earth with the same mass as Earth. Object A is a neutron star with the mass of the sun and object B is a iron cube with the mass of one gram. Will A or B hit the Earth at the same time or will one hit...
  44. Krushnaraj Pandya

    Height to which rolling ball rises on a surface

    1. The problem A ball moves without sliding on a horizontal surface. It ascends a curved track upto height h and returns. Value of h is h1 for sufficient rough curved track to avoid sliding and is h2 for smooth curved track, then how are h1 and h2 related (greater, lesser, equal or multiplied by...
  45. Krushnaraj Pandya

    Rolling on a plank which is resting on friction less surface

    Homework Statement A long plank of mass M rests upon a smooth horizontal surface. A thin circular ring (m, R) slips (without rotation) upon the plank with initial velocity v(i). The coefficient of friction between the wheel and the plank is C. at time t, the ring stops slipping and pure rolling...
  46. Felipe Lincoln

    Stokes' Theorem, how to apply for this surface?

    Homework Statement With the stokes' theorem transform the integral ## \iint_\sigma \vec{\nabla}\times\vec{F}\cdot\vec{\mathrm{d}S} ## into a line integral and calculate. ## \vec{F}(x,y,z) = y\hat{i} -x^2\hat{j} +5\hat{k}## ##\sigma(u,v) = (u, v, 1-u^2)## ## v\geq0##, ##u\geq0##...
  47. M

    Flux with an infinitely long surface cutting through a sphere

    Homework Statement Bildschirmfoto 2018-06-19 um 18.50.50.png In the y-z plane there is an infinite long surface with charge density ##\sigma## that slices through a sphere with radius R. Determine the Flux.The Attempt at a Solution I have solved the problem but am stuck at the last part. I used...
  48. joyxx

    Weight of person on Earth, and on a different planet's surface?

    Homework Statement A) What is the weight (in Newtons) of an 80 kg person at the Earth's surface? B) What is the weight of the same person on the surface of the planet with a mass 8.0 x 10^24 kg and a radius of 5.5 x 10^6 m? (G=6.67 x 10^-11 N*m^2/kg^2) C) what is the apparent weight (scale...
  49. E

    A Surface states of 3D topological insulators

    I have a question (more like a curiosity) related to three-dimensional topological insulators, which support Dirac-like states at their surfaces. From the theory, it is well known that these states are immune to scattering from non-magnetic impurities, i.e. impurities that do not break...
  50. srm

    Calculation of the weight of an insect floating by surface tension

    Homework Statement The surface of a liquid is just able to support the weight of a six-legged insect. The leg ends can be assumed to be spheres each of radius 3.2 × 10−5 m and the weight of the insect is distributed equally over the six legs. The coefficient of surface tension in this case is...
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