Surface Definition and 1000 Threads

Homework Statement The Earth receives on average about 390 W m−2 of radiant thermal energy from the Sun, averaged over the whole of the Earth. It radiates an equal amount back into space, maintaining a thermal equilibrium that keeps the average temperature on Earth the same. Assuming the Earth...

Homework Statement This is problem 3.4 from Prucell and Morin if you have the book. Homework Equations None The Attempt at a Solution Electric field inside a conducting sphere is zero. Let P be a point on one of its equatorial plane. The field along the plane is zero. So I know the charge...

Hi , I came across a problem ,I've search a lot but couldn't exactly find the solution. here is my problem: suppose there is an image ( I call it IMG_A),place IMG_A in the X-Y plane , put a mirror cylinder at the center of IMG_A. what we see in the cylinder mirror is a deform image (I call it...

Hey all, Interestingly enough, I was actually recently feeding some ducks at a nearby pond when I noticed a cool phenomenon that I couldn't explain myself, so I was hoping you guys could assist in that. When you have two air bubbles over a liquid surface, like water, they seem to accelerate...

The motivation for this thread comes from physics, but I'm posting it in the maths section as the question is more of a mathematical one and less concerned with the underlying physics. In cosmology, they often talk about closed universes with positive curvature, or non-Euclidean elliptic...

Homework Statement By finding the Lagrangian and using the metric: \left(\begin{array}{cc}R^2&0\\0&R^2sin^2(\theta)\end{array}\right) show that: \theta (t)=arccos(\sqrt{1-\frac{A^2}{\omega^2}}cos(\omega t +\theta_o)) Homework EquationsThe Attempt at a Solution So I got the lagrangian to be...

Homework Statement Electric current of I amperes flows along the z-axis from (0, 0,-∞) to (0, 0, -a) and from there it spreads over a conducting sphere r = a in the -aθ direction, comes to the point (0; 0; a) and goes to (0, 0, ∞) again along the z-axis. What is the surface current density at...

I have a free particle moving on the surface of a sphere of fixed radius R. Gravity is ignored and m/2 is left out since its constant. The lagrangian is L = R^2 \dot{\theta^2} + R^2 sin^2{\theta} \dot{\phi^2} Using the Euler Lagrange equations I obtain sin^2{\theta} \dot{\phi} = A = const \...

Homework Statement The free fall acceleration of a mass ##m## above the Earth's surface in one dimension can be represented by ##m\ddot{y}=-\frac{mMG}{y^2}## where ##M## is the mass of the Earth and ##G## is the gravitational constant. With ##\dot{y}(t=0)=0## and ##y(t=0)=y_0##.. (1) Find an...

Hello all, new here but plan to stick around for a while. I am currently trying to make a sensor that can detect if a material below it is paramagnetic. I believe paramagnetic is the proper term, but it needs to detect if the force exerted by permanent magnet is above a certain threshold. The...

Homework Statement Ball strikes inclined plane of infinite mass with velocity v vertically. Elastic collisions. Velocity and direction after collision? One way of solving is take components along and perpendicular to inclined plane and then solve easily. Is there any way to solve is using...

Homework Statement i don't understand the statement 1 and 2 , can someone help to explain ? for 1 , does the author mean Fh= Fv ?? for 2 , does the author mean Fv = Fh + W ? but in statement 1 , Fh already = Fv Homework EquationsThe Attempt at a Solution

Homework Statement An infinitely long, cylindrical, conducting shell of inner radius b and outer radius c has a total charge Q. A line of uniform charge distribution Λ is placed along the axis of the shell. Using Gauss's Law and justifying each step, determine. A) The Electric Field for r>a...

Hello If we have a gaussian surface that is placed in a uniform electric field E and encloses 0 charge, what would the E-field at the gaussian surface be? I have assumed the gaussian surface to be cubic surface, and then I have found from Gauss's law that the electric field is zero at the...

https://www.google.ca/search?q=stress&biw=1366&bih=629&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjA9u3S5_jKAhXCJx4KHfN8DmYQ_AUIBigB#tbm=isch&q=stress+tensor&imgrc=xK8-tGSPxXha7M%3 This is a simple question. -why stress is defined on 3 surfaces only instead of the entire 6 surfaces? I believe 3...

Homework Statement A closed surface with dimensions a = b = 0.302m and c=0.604m is located as in the figure. The electric field throughout the region is nonuniform and defined by E⃗ = (α+βx2)ˆı where x is in meters,α=4N/C, andβ=4N/(C·m2).? What is the magnitude of the net charge enclosed by the...

Homework Statement I have this problem in an online assignment. Someone told me the answer, so I already got it right, but I don't know why my logic leads me to the wrong answer. The problem: The temperature u of a star of conductivity 1 is defined by u = \frac{1}{sqrt(x^2+y^2+z^2)}. If the...

Why he did not consider parallel force?Will parallel component of electric field not produce electric pressure on the surface?

Homework Statement [/B]Homework Equations Poynting's Theorem S = 1/μ0 (E x B) Momentum = p = μ0ε0 ∫ S dτ The Attempt at a Solution My strategy was to treat the hollow sphere as a point charge (by Gauss' Law), so E = 1/4πε0 Q/a2. I believe the magnetic field would be B = 2/3μ0M (where M is the...

In my physics textbook, I see Gauss' Law as https://upload.wikimedia.org/math/0/3/5/035b153014908c0431f00b5ddb60c999.png\ointE dA but in other places I see it as...

Old article: http://edition.cnn.com/2009/TECH/science/08/28/hurricanes.gates.gray/ What do you guys think? Where do you see this project going? The official word is that it's not being publicly funded. But if there was even a 10% chance it would work, I see governments lining up at the...

Homework Statement Evaluate integral A.n dS for A=(y,2x,-z) and S is the surface of the plane 2x+y=6 in the first octant of the plane cut off by z=4 Homework Equations Integral A.n dS The Attempt at a Solution The normal to the plane is (2,1,0) so the unit normal vector is 1/sqrt3 (2,1,0)...

hi guys, i have a question. i saw this picture, and i don't really understand how they derived with the formula. The aim is basically to find the formula for the surface area of a spherical cap. why do you differentiate the x=sqrt(rˆ2-yˆ2)? how does that help to find the surface? and then...

Hey! :o I want to calculate the surface integral of $$F(x,y,z)=(0,0,z)$$ on the unit sphere with parametrization $$x=\sin u \cos v, \ y=\sin u \sin v , \ z=\cos u \\ 0\leq u\leq \pi, \ 0\leq v\leq 2\pi$$ with positive direction the direction of $T_u\times T_v$. Could you give some hints how...

Hi PF! I have been reading and reading for a clean explanation for the hydrostatic force of a curved submerged 2-D (or 3-D if you're up to it) surface. I really don't care what the curve looks like: quadratic, circular, partway sinusoidal, etc. All articles I read involve the centroid, but...

Take two lasers of the same intensity and wavelength and aim them at 30 degrees at the same spot on a mirror, so that at the surface the waves cancel perfectly. What happens? How can the wave be reflected if there is no field present?

So I'm reading that ice (solid) always has a liquid surface if it's surrounded by a gas. Does this mean every solid (e.g., my dining room table) also has a liquid surface because it's surrounded by gas? It doesn't seem to have a liquid surface. :-/ If something sublimes it skips this phase so I...

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...

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)...