Surface Definition and 1000 Threads

Homework Statement First I will say, I know I post here alot, but that is because I have exams coming up soon and I am a beginner, and It's crunch time, I'm self taught with only the help of friends and the internet. I'm currently doing a past examination as practice, but this one is much...

My question is basically similar to a thread that was posted 12 years ago: https://www.physicsforums.com/threads/electrons-flying-off-a-conductor.119269/ I was glad to see that there was already a thread which asked my question in the forum. But when I read through all of the discussion, I don't...

Fluid comes in at ##T_1## and comes out at ##T_2## and I know that heat is exchanged with steam at constant ##T_{steam}##. If I want to know the Surface of the exchanger then ##US(T_{steam}-T_{fluid}) = \dot m_{fluid} cp_{fluid} (T_2-T_1)## My question is, since ##T_{fluid}## changes, which...

Homework Statement The tension in the skin of the left ventricle of heart is 4.90 N/m. A cut is made on the left ventricle during surgery. How many stitches must be used to repair the cut? Each stitch will safely support a tension of 0.4 N. Homework Equations Surface tension = force/length...

What is the value of electric field at the surface of a spherical shell?

Homework Statement The surface area, A, of a cylinder with height, h, and radius, r, is given by the equation ##A=2πrh+2πr^2##. A company makes soup cans by using 32π square inches of aluminum sheet for each can. If the height of the can is 6 inches, find the radius of the can. Homework...

Homework Statement Show that the surface and volume element on a deformed sphere are \sigma = \frac{\rho^2 \sin \theta}{\cos \gamma} d\phi d\theta, dV = \rho^3 \sin \theta d\phi d\theta, if \gamma is the angle between normal vector and radius vector. Homework Equations n\cdot r = \cos...

Does the event horizon of a black hole really represents the surface of the "star" (or mass) itself? What I mean to say is: That the event horizon is the (let's say it this way) sphere surface where the scape velocity is => than the speed of light. So it is not necessary for event horizon to be...

When studying Fresnel equations in EM, I very often came across the following type of picture for a s-polarized incident wave on a dielectric interface (http://iqst.ca/quantech/pubs/2013/fresnel-eoe.pdf) : Many similar diagrams can be found on the internet, for instance...

I have a surface defined by the quadratic relation:$$0=\phi^2t^4-x^2-y^2-z^2$$Where ##\phi## is a constant with units of ##km## ##s^{-2}##, ##t## is units of ##s## (time) and x, y and z are units of ##km## (space). The surface looks like this: Since the formula depends on the absolute value of...

What will be the area of common surface of two identical bubbles of radius R , i know there common surface will be flat as the radius of curvature of comman surface will tends to Infinity , but how do i relate with area of flat surface I tried to use Energy = Surface tension * area And then...

Hi .how can i calculate the molar volume and surface tension of nanoparticles ? shoud i have to calculate? or these parameters is available in tables or sth?

Well, my physics teacher taught us about rotation the other day and I came across a scenario where a sphere and a ring roll down a friction-less inclined plane from a point of absolute rest. I found it counter-intuitive as I started to think about why would they start rolling in the first place...

Homework Statement Homework EquationsThe Attempt at a Solution ## v = \frac { \omega } k ## ## \omega = \sqrt{ kg \tanh (k) } ##I have no idea to guess the graph. I put g = 9.8 and tried to calculate ## \omega ## for different values of k. ## \omega (0 ) = 0, \omega (30) =...

Homework Statement Everything that can be used is in the picture. μ is the coefficient of friction between both B and A and A and the surface. A is moving upwards the surface with a certain acceleration. B doesn't move in relative to the surface. 1. Why the direction of A's motion must be...

Homework Statement Homework Equations I consider four directions from the point of throwing the balls, east, west, up, down. At any given time, the balls will be at different distance from this point, (the upward ball will travel less distance than the downward ball). So, it could not be a...

Homework Statement A body that is on a horizontal surface begins to move under the action of horizontal force equal to 60% of its weight. Force acts for a while, then stops acting. Determine the total time of movement if the body has traveled a distance of 24m. Homework Equations [/B] I'm...

Homework Statement Homework EquationsThe Attempt at a Solution [/B] The thing to remember is that inside the Earth surface, the gravitational field does not remain inversely proportional to ##r^2##. The equation of motion is ## \ddot r = \frac { -gr} R## ....(1) This means that the...

Hi, I am quite confused about followed question, I think scientist think the last scattering surface was dense plasma at the temperature of 3000K. If the today's universe much cooler and less dense then "the last scattering surface" how can anyone says entropy increased by time? Isn't universe...

I need help understanding what kind of problem this is at all, since I'm really lost. I'm missing the specific topic name (I called the topic "circular motion" because it's got something to do with it, but maybe it has a more specific sub-topic name), probably missing key formulas, and generally...

I am using a Micromeretics ASAP2020 machine. The sample is ~25mg of reduced graphene oxide based film. The problem is I am getting adsorption isotherms showing negative volumes of adsorbate (N2) entering the tube as P/P0 increases. The sample was degassed prior to testing at 250°C for 3...

Let's imagine a situation where we have a wheel of mass ##M## and radius ##R## on a frictionless surface, and we apply a force ##\vec{F}## as shown in the diagram. The force will produce both linear acceleration of centre of mass ##a## and angular acceleration ##\alpha##. The wheel starts to...

Homework Statement The surface tension of a layer of water obeys ## \sigma = a- bT##, where ##T## is the temperature. Find the change in temperaure, ##\Delta T## when the area is increased isentropically. Homework Equations ## dU = dQ -dW## , ##dW = \sigma dA##, ##dU = C_A dT + [\sigma...

Homework Statement Consider a cyclinder made of linear dielectric material with uniform dipole distribution. An externally applied field ##E_{ext}## is applied in the direction parallel to the axis of the cyclinder. What are the values of the bound chrages at the surface. Homework Equations...

It will be very helpful if someone suggest any articles or reading materials on this topic for detailed study.

If I take a rod of length L and lay it down on a surface with no friction and act upon it with a force F off its center of mass by let's say L/4, there will be a torque on the object and it will start to rotate around its center off mass. My question is why does the object necessarily rotate...

At a force of 40N, the body moves along a horizontal surface with an acceleration of 2m/s^2 and under the action of 50N with an acceleration of 3m/s^2. What is the mass of the body? F1 = 40N a1 = 2m/s^2 F2 = 50N a2 = 3m/s^2 _____________ m=? 2. Homework Equations As there's no...

$\tiny{x4.01}$ $\textsf{Find an equation for the level surface of the function}$ $$f(x,y,z)=x+e^{y+z}$$ $\textsf{ that passes through the point}$ $$(1, \ln(4), \ln(9))$$

Hey! :o If $0\leq a<b$, I want to calculate the area of the conic surface that is defined by the relations $z^2=x^2+y^2$ and $a\leq z\leq b$ in two ways: using cartesian coordinates using cylindrical coordinates I have the following: We have that $z^2=x^2+y^2\Rightarrow z=\pm...

I'm trying to figure out what happens to a tension-ed anchor line when encountered by a surface wave (transverse and longitudinal ) Assuming a 2 dimensional view, or that the cable is sufficiently wide that the wave cannot go 'around it' what happens to the path and speed of the surface wave...

Does anyone have a good reference for work on surface excitons? I am in particular interested in excitons on surfaces of metal oxides (TiO2, Al2O3 etc) I've spent a fair amount of time trying to find information using Google Scholar etc. My (old) undergraduate surface science textbook does have...

The Theia hypothesis is the current leading hypothesis to explain how our moon was created. Both Earth's mantle and the moon's surface have indistinguishable oxygen isotope ratios, which leaves the earth–moon system as more similar in O isotopes than any other two bodies in the solar system...

Homework Statement Homework EquationsThe Attempt at a Solution Since the wheel is rolling , vcm=ωr , acm = αr The wheel is in pure rotation about the point O where it touches the surface . The point P is a distance 4/3 from the bottom point . Angular acceleration of the point = 3 rad/s2...

Homework Statement I have a project to research the effect of surface roughness on wing performance. I found mostly that roughness leads to increased drag on a wing, however came across a website that briefly spoke about how recently researchers have observed how carefully selected roughness...

A torus with major radius, ##R##, and minor radius, ##r##, has a total surface area given by ##4\pi^2 Rr##. If one slices the torus on its midline (i.e. at a line on a poloidal angle of ##-\pi/2## and ##\pi/2##), I was told the inner half of the torus has a smaller surface area than the outer...

first thing first i want you to excuse me for my Grammar or spelling cause i am really bad at both !we know that what gives the thing gravity is the mass the mass warp the space-time fabric but Jupiter has a low mass than earth how does it have all this amount of gravity or the warping in the...

2 SEM images of gemstones: emerald and ruby (Electron Miscroscope with Secondary Electron detector, (which "takes picture" of surface layer (~0.5 um) both the elemental composition and relief)). Dendrites - it is clear (not me, but in general), what creates other patterns? * trace elements? -...

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 ?

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)...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...