Surface Definition and 1000 Threads

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...

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?

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...

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...

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...

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 ?

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...

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...

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...

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...

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...

----------------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...

Hi! it's been a day since I have started this problem. I was wondering how I could arrive to this Hamiltonian? And I'm a bit at a lost on how exactly to derive this? I hope anyone can help me with this, even a suggestion of good starting point would be much appreciated. Basically the problem...

This is not a homework, but a question formed in my mind after reading my textbook. Homework Statement Consider an electron (a charged particle) on a metallic equipotential surface. We know that all the points on the surface are equipotential, thus there will be no force on charged particles...

Hi guys, I've got an exam in a few days and my lecturer is unresponsive, so wondering if you can help me. The question I am solving is the following: Calculate the impedance at the surface of a layer of spruce wood of thickness d equal to 2mm, and of density rho equal to 0.47 Mg/m3 at...

"Suppose a body is kept on frictionless surface (considering gravity is acting on a body). If we give a little push to the body, will it conitnue to be in state of motion with constant velocity or not?...If yes then why?? (Considering all resistances to be zero ..)

<< Thread moved from the technical forums so no Homework Help Template is shown >> Hello, I'm attempting an experiment where I take a cart and slide it down a ramp. Each time, I will coat the ramp with a different liquid. I want to compare the effects of the dry ramp, a ramp with water poured...

I'd like to use 2-d for simplification. Divergence is the rate of change of a component of a field F as you travel along that component's direction. So Fx represents the part of F flowing the X direction and same with Fy along the Y direction, and so divergence is calculated by dFx/dx +...

Assuming that the temperature in the tire suddenly rises. My question is that would that cause the contact surface area between the tires and the floor increase, decrease, or stay the same? (given that the volume of air in the tires is a constant and cannot be changed) Also, why?

I have done it by the parametric form of σ, but if I change σ to implicit form that is G(x,y,z)=x^2+y*2+z^2-R^2=0 I don't know how continue. The theory is: where Rxy is the projection of σ in plane xy so it's the circumference x^2+y^2=R^2

I don't understand why materials with low surface energy are hydrophobic and viceversa. All I can find are quick phenomenological explanations that don't quite deal with the physical (microscopic) process going on. Could anyone provide a good microscopic picture of why it is that way? What's...

Hi there, I noticed that when I release the cap it moves forward slightly (away from me) which I attribute to the surface being not level and my hand applying a small force. However, the cap will roll backwards afterwards (towards me). What is causing the cap to roll back and forth? It...

Is a surface bounding a volume always a closed surface?

Homework Statement Ball falling from 1m above a slanted surface 5 degrees from horizontal. KE conserved Find distance traveled along slanted surface on its second rebound Homework Equations S=(1/2)(at^2) (V^2)=(u^2)-2as The Attempt at a Solution V before hitting =sqrt(2*9.81) =4.42...

This seems basic, but I'm stuck. Look at the attached picture. I'm trying to find the temperature on the outer surface of the insulation. Is it not possible because I do not know the rate of heat transfer? How do pipe designers know the required thickness of insulation needed to reduce to a...

Homework Statement coefficient of kinetic friction between the disk and the surface is 0.42 gravity = 10.6 m/s disk mass = 1.75x10^9 the skid marks are 1280m long, This is due to the fact that uneven friction had set the saucer in very slow rotation around its principal axis. By...

I want to calculate the pressure profile inside a cylinder whose initial pressure is less than the outside pressure and has a orifice on its surface to flow air through it. Air is a considered as compressible ideal gas and mass flow rate across a orifice is assumed isentropic. Also the...

Let's suppose we have a cuboidal tank filled with liquid of density rho,such that Critical angle of medium is (Ic) now it's Clear that light rays from the medium that strike at proper critical angle will Graze along the surface Now if someone would be along the path of the rays receiving...

Homework Statement Solve the surface integral ##\displaystyle \iint_S z^2 \, dS##, where ##S## is the part of the paraboloid ##x=y^2+z^2## given by ##0 \le x \le 1##. Homework EquationsThe Attempt at a Solution First, we make the parametrization ##x=u^2+v^2, \, y=u, \, z = v##, so let...

I'm (self)studying the physics of heat transfer at the moment. My book gives a relationship between heat transfer rate and thermal resistance as ##\phi=\frac {A \Delta T} {R}##. My book is not in English, so hopefully that is not the cause of this misunderstanding. I double checked that heat...

Consider the following two definitions of the surface gravity of a black hole (taken from page 23 of Thomas Hartman's lecture notes(http://www.hartmanhep.net/topics2015/) on Quantum Gravity): 1. The surface gravity is the acceleration due to gravity near the horizon (which goes to infinity)...

Today I was speaking with a professor and he asked me, regarding fluids, what is pressure. I said force per unit area acting normal to a surface. He then asked what I meant by surface. I wasn't really sure how to respond. He also asked me what surface tension was. I said it is a force per unit...

Rita wants to cover a roughly rectangular area with netting. The height is 9 feet (but one side is along a solid fence, so could be 4 feet), two sides are each 6 feet, and the other side is 5_1/2 feet. How much netting does she need? Netting comes as a rectangular or square piece. My Work:Let A...

Very dumb classic mechanics question here: The other day I caught sight of a trivial objects arrangement: a basketball placed on top of a 6-sided cardboard box on the floor, and I wondered how the weight of the hollowed sphere could cause bending on the supported, flat top surface of the box...

I'm hoping someone can help check whether my final contour plots look plausible based on the surface. I haven't done too much differential geometry but I've needed to work with Gaussian/Mean curvature for a simple 3D gaussian surface. Here's an example: (A = 7, a=b=1/(3.5)^2) It's...

To find the surface area of a hemisphere of radius ##R##, we can do so by summing up rings of height ##Rd\theta## (arc length) and radius ##r=Rcos(\theta)##. So the surface area is then ##S=\int_0^{\frac{\pi}{2}}2\pi (Rcos(\theta))Rd\theta=2\pi R^2\int_0^{\frac{\pi}{2}}cos(\theta)d\theta=2\pi...

Aluminum metal covers itself immediately of an oxide layer in air. This layer is quite thick, more than 0,01mm they say and it's non-conductive. This layer infact is, e.g., thick enough to prevent soldering, further chemical attack by air oxygen or water (with which nude Al would immediately...

Minimal surfaces are sort of the "shortest path" but in terms of surface shapes. So I figured I could characterize the shape of a hammock by adding the influence of gravity, much like you can get the shape of a catenary cable (y=cosh(x)). The equation of motion I get from the Lagrangian is...

I would like to know why electric field of EM waves changes it's direction to opposite when hitting a conductor surface. I know that electric field inside a conductor is zero but I am not able to connect these two situations.

Hey y'all, my first thread here, Got a burning question that has been disturbing my serenity. In all derivations of the stress tensor that I've seen they didn't explain it that much, So my question is, why do the traction vectors on each surface are independent? From what I understood, the...

Hi, I need to choose a hydraulic hub motor for a vehicle which weighs 25 000 N when fully loaded. The vehicle must be able to start moving (fully loaded) on a inclined surface (30 degrees angle). So I need to determine the torque needed to get vehicle moving. The vehicle has three wheels from...

Homework Statement Homework EquationsThe Attempt at a Solution I don't understand how it looks like, how to approach this problem. I think it's maybe image charge or Laplace equation

Hello My geometry is a prototype of a hydroelectric plant. It consists of a tank, penstock, a gate and a test section; my aim is to simulate turbulent flows on this prototype. My geometry consists of two zones, a zone filled with water (red color) and a zone filled with air (blue color). The...

Homework Statement Hi guys I am a bit stuck on how I am suppose to show, that thse funcitons are normal to level surface. I am I suppose to do a derivation of some sort, alls my notes say in a tiny box, that grad f is always in the direction to the normal of the surface. Do I have to calculate...

I am working om multilayer hybrid plasmonic waveguide (Si-SiO2-Ag_SiO2-Si). I have to see effect of roughness on propagation length and other parameters. So in reference to that I am having some doubts: 1) I use CST microwave studio for numerical simulation. I am not getting any direct option...

I am investigating the nucleation on solid surface during liquid-liquid phase separation, I know the free energy change is and I don't know if it is correct to get Can someone calculate it to have a check?

Homework Statement Why does gravity force decreases below Earth's surface? Homework Equations F = G (m1 m2)/r^2 F = force of gravity G = Universal gravity constant m1 and m2 = mass of the objects r = distance between two objects g = GM/r^2 g = gravity of the object G = universal gravity...

In an attempt to explain why a matt surface of aluminium is a better emitter/absorber of blackbody radiation than shiny surface of aluminium, my university lecturer suggested to me that: By brushing a metal surface to create a matt finish, the surface of the metal becomes rougher. Rougher means...

hi everyone, i have a mcnp error, it don't finish, it only run a half! i hope someone can help me! thank you! and my code JCO c cell cards 1 1 -0.00117 -100 300 2 2 -1.52 (-100:-101) -300 #1 $solution 3 4 -7.93 (-110:-111)#1#2 $clad 4 3 -1 (-200:-201)#3#1#2 $water 5 4 -7.93...

Okay, so in Griffith's introduction to electrodynamics, Griffith clearly defines surface current density as follows: "when charge flows over a surface, we describe it by the surface current density, K. Consider a 'ribbon' of infinitesimal width dL running parallel to the current flow. If the...