Surface Definition and 1000 Threads

Idk where i picked this up, but there is one other plausible colony destination for humans: Venus. After a few trips on the net, I've come to the "Aerostat on Venus" side instead of a colony on mars. I'll mention some of the reasons I've picked up as to why: 1. Tons of CO2, we can use that. 2...

Homework Statement Consider a massless rod of length $L$ with a small mass $m1$ attached on one end, and $m2$ attached on the other end. The rod is initially in the vertical position at rest on a frictionless surface, with $m1$ on bottom and $m2$ on top. A small impulse is applied to the top...

Hi! I wondering does anyone here has a clue of lowering the absorption level and narrowing the scattering bandwidth of LSPR of nanoparticles? Are those "intrinsic" properties or can be improved by modifying their size, shapes, etc? Thanks for sharing your thoughts! Paul

Homework Statement Find the area of the part of z^2=xy that lies inside the hemisphere x^2+y^2+z^2=1, z>0 Homework Equations da= double integral sqrt(1+(dz/dx)^2+(dz/dy)^2))dxdy The Attempt at a Solution (dz/dx)^2=y/2x (dz/dy)^2=x/2y => double integral (x+y)(sqrt(2xy)^-1/5) dxdy Now I'm...

a thin film of water has surface tension due to the strong bonds present on the surface in order to counteract the net downward force and this increases the potential energy of the surface layer of particles therefore on a hydrophobic surface it forms a water droplet , my question is since it...

Homework Statement I am having trouble with part iii) of the following problem: Verify the divergence theorem for the function ##\vec{u} = (xy,- y^2, + z)## and the surface enclosed by the three parts: (i) ##z = 0, x^2+y^2 < 1##, (ii) ##x^2+y^2 = 1, 0 \le z \le 1## and (iii)...

I am trying to find the temperature of a star given its wavelength in micrometres, but I am not sure if my conversion is right therefore don't know if the answer is correct. Star A has a maximum emission wavelength of 1 μm and Radius 100 Rsun. What is its Effective Temperature and Luminosity...

Homework Statement Why the weight of water at water surface is given by formula 2(pi)Rσ(cos angle) ? Homework EquationsThe Attempt at a Solution

Hi there people! So my question is why you can see localized surface states within the band gap of the material with an STM. How is a tunneling circuit being established?

So far I have calculated this for a cone, which elegantly results in the conic sections. However, I would like to do this for the other quadric surfaces. Is the calculation for this been published anywhere online?

Let's say we have a car going up a 10% grade that slams on the brakes. The normal force would be mg(cos angle of elevation) in a component of Fg that is perpendicular to the road surface, and there would be a direct effect of gravity in the component of Fg that is parallel with the road...

I have a stepper exercise machine that stands on four legs and I would like to place this machine on a shelf made of canvas cloth ( the whole wardrobe is made of canvas ). The problem is I think the shelf would tear where the four legs are. So I would like to ask if there is any way I could...

I have a stepper exercise machine that stands on four legs and I would like to place this machine on a shelf made of canvas cloth ( the whole wardrobe is made of canvas ). The problem is I think the shelf would tear where the four legs are. So I would like to ask if there is any way I could...

Q:- Describe equipotential surface due to a uniform grid consisting of long equally spaced parallel charged wires in a plane. The answer given in my textbook is - Equipotential surface have shape which changes periodically. At far off distances it becomes parallel to the plane. Why the...

"A metallic wall cannot, however, support an electric field parallel to the surface, since charges can always flow in such a way as to neutralize the electric field." This is from a textbook and I'm not quite sure what this means. The context is the process of calculating Rayleigh and Jeans...

Hello all, - first of all sorry for my bad english, it's not my mother tong. - I write here because I want to understand that are the surface waves and how can we demonstrate their existence ? Do you have a PDF file which speak about this ? - For volumic waves I have seen a mathematical...

I was asked to explain how different factors affect surface tension. I can understand how temperature plays a role. 1) Contamination: Increase in contamination decreases surface tension. I tried thinking about it.I thought maybe the particles that contaminate the fluid get in the way and...

Homework Statement What should be the pressure inside a small air bubble of 0.1,, radius,situated just below the surface? st of water=7.2 *10-2 and atmospheric pressure=1.013*105. Homework EquationsThe Attempt at a Solution I am of the understanding that the pressure inside the...

Hi, i would like to know how to do this question for fluid mechanics. Sorry as I am new i didnt know how to upload images so i just uploaded the image in justpaste, here is the link http://justpaste.it/pz7r

How, if at all, would differential geometry differ between the opposite "sides" of the surface in question. Simplest example: suppose you look at vectors etc on the outside of a sphere as opposed to the inside. Or a flat plane? Wouldn't one of the coordinates be essentially a mirror while...

Homework Statement Hi, as a part of my lab report I have to conduct this experiment : Fill a pot with tap water and boil it, determine then how much of the energy that the kitchen surface produced, actually went to the water itself. Consider the water having an initial temperature of 10 °C. In...

There is a distorted surface and the source of the flux is inside the cube I have read that flux through it would be q/2ε0 I want to know Why?It is not my homework problem and I think it does not involve any calculation that's why I did not post it in homework section .There should be some...

Joos asserts on page 31 https://books.google.com/books?id=btrCAgAAQBAJ&lpg=PP1&pg=PA31#v=onepage&q&f=false that $$\nabla \times \mathfrak{v} = \lim_{\Delta \tau \to 0} \frac{1}{\Delta \tau }\oint d\mathfrak{S}\times \mathfrak{v}$$ I tried to demonstrate this, and neglected to place the surface...

Homework Statement A large sphere exists in space, which has a mass of 1 * 10^28 kg The sphere has a radius of 100,000 km What will be its gravitational pull (aka: "relative gravity") on its surface in terms of gs (1 "g" being equal to the gravitational pull of the Earth which is 9.807 m/s^2)...

The HadCRUT4 global surface temperature anomalies in tabular form include confidence intervals. The GISS surface temperature data is available in tabular text form here http://data.giss.nasa.gov/gistemp/tabledata_v3/GLB.Ts+dSST.txt - but it doesn't include any confidence intervals. Can...

What is the "plane of symmetry", "zero velocity wall" and "free surface" terms which I have seen in Polyflow? It says in Vnormal=Fs=0 for plane of symmetry and Vnormal= Vs= 0 for zero velocity Wall. Now I get when Vs=Vn=0 it means that the wall isn't moving and it's in a static state but didnt...

Homework Statement How do I find the surface area of a sphere (r=15) with integrals. Homework Equations Surface area for cylinder and sphere A=4*pi*r2. The Attempt at a Solution I draw the graph for y=f(x)=√(152-x2). A circle for for positive y values which I rotate. I will create infinite...

The following is my interpretation of the development of the divergence of a vector field given by Joos: $$dy dz dv_x=dy dz\left(v_x(dx)-v_x(0)\right)=dy dz\left(v_x(0)+dx\frac{\partial v_x}{\partial x}(0)- v_x(0)\right)$$ $$=dy dz dx\frac{\partial v_x}{\partial x}(0)=d\tau \frac{\partial...

Homework Statement Compute the average number of molecular hits, per unit time, experienced by a square inch of surface exposed to air, under normal conditions. Assume air is a mixture composed of 80% N2, 20% O2, both of which are assumed to be ideal gases. You will have to perform angular...

Homework Statement The plane with surface charge sigma lies in x-z plane at y=0, parallel to it at y=a there is a grounded plane. What is the field just above the bottom plane, find the potential between the planes Homework Equations discontinuity E=sigma/epsilon, V=Qd/Aepsilon take the...

We are currently trying to measure pH levels on the (wet) surface of metals as part of a study about corrosion. The surface may have a non-conductive protective layer. - is it feasible to measure pH on a planar surface (dry or wet)? Which kind of sensor probe can be used for this task? -...

I was just looking through a few different solutions in Griffiths EM and I must have not realized it, but do bound and free charges both contribute to the overall electric field? For example: when dealing with a capacitor with a dielectric between it, one of the solutions wants to find the...

Hello guys, Consider a partially filled tank with water where the acoustic field can be described by the Helmholtz equation. The boundary condition at the water surface would be \frac{∂p}{∂\vec{n}} = -j\rho_0\omega\frac{p}{Z} where Z is the impedance of the water surface. What would be...

Hello guys! I have to model the acouctic field within partially filled cavities. So consider a rectangular or cylindrical cavity that is partially filled with water. I would like to model the water layer as a sound absorbing wall by prescribing it as a surface impedance boundary condition...

Homework Statement New to physics forum, so please forgive me if I am posting this in the wrong place, but it seems to me that this is a homework-type or basic physics question. Here it is: You have a perfect cube with substantial mass sitting on a flat frictionless surface. The surface plane...

Homework Statement A cylindrical container of water with a radius of 6.0 cm is placed on a phonograph turntable so that its outer edge just touches the outer edge of the turntable. The radius of the turntable is 14.5 cm, and the turntable rotates at 33 and a 1/3 revolutions per minute. How much...

Homework Statement A child stands on frictionless ice and throws a snowball. Estimate the recoil velocity of the child. Homework Equations m1v1i + m2v2i =m1v1 +m2v2f 1/2mv21i + 1/2 mv22i = 1/2 mv21f + 1/2mv22f The Attempt at a Solution After choosing estimates for weight of snowball, speed of...

Homework Statement Wikipedia tells me that I can obtain the surface area of a sphere by realizing that the volume of a sphere is equivalent to the infinite sum of the surface areas of hollow, nested spheres, sort of like little Russian dolls. That makes sense, and then differentiating both...

Homework Statement A 3 m long gate of weight 4 kN per unit width is hinged at O and sits at an angle θ as a function of water height h above the hinge. (A) Using a y-axis measured up from the hinge, derive a general relation between h and θ, with all other variables evaluated in the relation...

I am trying to figure out the flux surface average of a 3D perturbation in a tokamak. For example what is the flux surface average of cos(m*theta+n*phi) at a given flux surface. (Theta and phi being poloidal and toroidal angles respectively?

Hi everyone. I'm looking for some help from someone expert in optics to create an inteferometry based setup to map the surface of a small object. This is for a small lab project so I'm not looking for a really complex setup, I just need something simple that can be built in a short amount of...

Homework Statement [/B] Homework Equations ##\vec{E}##=##\frac{∂V}{∂r}## The Attempt at a Solution I have provided both problem and solution(almost)but the problem is I did not understand the solution.First of all I did not understand the question what we are told to determine? I locate the...

Homework Statement \vec J_b = 3s \hat z \int \vec J_b \, d\vec a I need to solve this integral in cylindrical coordinates. It's the bound current of an infinite cylinder, with everything done in cylindrical coordinates and s is the radius of the cylinder. The answer should end up with a phi...

Hi, I've been doing reading on Halbach Arrays moving over surfaces and generating repulsive forces. From my understanding, the moving magnet induces a circular electric current in the metal track, which gives rise to a magnetic field. However, I'm having trouble understanding why this field...

We just started going over line integrals in calculus, and have been told that the integral over any closed surface is 0. What I don't get is then why can we do the line integral of a circle to get 2##\pi##r? Since a circle is a closed surface, shouldn't the line integral then be 0?

I have recently had a series of lectures on X-ray physics. I have been quite confused by the concept of effective dose and entrance surface dose. I have been told that entrance surface dose varies proportionally to kV squared. I have also been told that as kV increases, effective dose...

Hi, I am trying to get some information about why Matt black surfaces are such good emitters and shiny surfaces are not. When you try and look this up there really isn't much so I have tried to string what I have found together. Shiny metal surfaces have free electrons which cancel the...

1. Introduction Pressure of a fluid exerts thrust on each part of a surface with which the fluid made contact. Each forces distributed over the area have a resultant magnitude and direction that is very crucial. For a horizontal surface, the pressure does not vary over the plane. Thus, the...

Homework Statement Calculate the integral ##\oint_C \vec F \cdot d\vec S##, where ##C## is the closed curve constructed by the intersection of the surfaces ##z = \frac{x^2+y^2}{4a}## and ##x^2+y^2+z^2=9a^2##, and ##\vec F## is the field ##\vec F = F_0\left( \frac{a}{\rho}+\frac{\rho^2}{a^2}...

I'm trying to deduce the differential equation for temperature for a triangular fin: I know that for a rectangular fin, such as: I can do: Energy entering the left: q_x= -kA\frac{dT(x)}{dx} Energy leaving the right: q_{x+dx} = -kA\frac{dT(x)}{dx} - kA\frac{d² T(x)}{dx²}dx Energy lost by...