What is Section: Definition and 733 Discussions

I am trying to post a question in the physics section but the LATEX is misbehaving. It seems to be stuck on the equation for kinetic energy. Any LATEX command I put in always shows up as the kinetic energy equation. Any ideas on how to fix this? I have closed the web browser and opened it up...

Is it true in complete generality that every fiber bundle with contractible fiber have a global section? Or do some sort of restrictions on the bundle need to be made? I ran across a mention of this fact in Guillemin and Sternberg's "Supersymmetry..." and I'm not sure how to prove it.

Homework Statement Integrate the rutherford cross section over the backward hemisphere to get 4pi(sigma0(E)) Homework Equations Rutherford cross section is sigma0(E)/sin^4(theta/2) The Attempt at a Solution When I integrate this with the limits pi/2 to pi i get sigma0(E)*(8/3) i...

In the section shown here http://sites.google.com/site/juliansrealativity/_/rsrc/1271044270997/home/time-from-stationary.bmp" is the right hand side of the equation intended to refer to light in the moving frame, or to light in the stationary frame ?

What is physically meant by: \frac{d \sigma}{d \Omega} Where \sigma is the cross section and \Omega is solid angle. I can't really picture it.

Hi guys, I am trying to calculate the macroscopic cross section (scattering and absorption) for high energy neutrons between 1 MeV and 10^7 MeV in Silicon. I am using the macroscopic cross section to determine the mean free path. To calculate the macroscopic cross section, i need to know the...

Hey everyone, so I am in an Adv. Steel Design Course and I am supposed to design a beam under a given distributed DL+LL and Concentrated DL+LL. We are supposed to design the beam under two different conditions... a.) It has continuous lateral support b.) Lateral support is provided at the ends...

Homework Statement 3sinx = 1 + cos 2x Homework Equations N/A The Attempt at a Solution 3sinx = 1+1 - 2sin2x (Trigonometric Identity) 3sinx = 2-2sin2x 2sin2x + 3sinx = 2 I do not know where to go from there. My book tells me the answer is 30o and 150o

1. A string with linear density 2.0 g/m is strecthed along the positive x-axis with tension 20N. One end of the string, at x=0m, is tied to a hook that oscillates up and down with a frequency of 100 Hz and a max displacement of 1.0mm. AT t=0s, the hook is at its lowest point. a) What are the...

Hi. I was wondering how to calculate I and W for rectangular and quadratic tubes. I have formulas for massive rectangular and square sections and for circular tubes. I tried to make a formula for a square tube section, based on how the formula for the circular tube looks - but I didn't get...

Mod please move if this is the wrong section I',m sorry if it is. This is my first post on the site. I'm bummed about physics. I'm a biology major with hopes of going to med school. Chemistry and biology are super easy for me it I can do it in my sleep. but physics gives me difficulty. the...

The Rutherford differential cross section \frac{d\sigma}{d\Omega} goes like cosec(\vartheta)^4 which means at \vartheta=0 the differential cross section is infinite, which is ok. My question is, given that the differential cross section is proportional to the probability per unit solid...

thanks

My professor told me that the neutrons in a reactor see the surface area of nuclei, and not the the projected cross section. That really doesn't make intuitive sense. Is he right?

i know that τ=VQ/(Ib) now I am looking for the maximum stress so i will find that at the point at the centre of the rectangle Q=A*\bar{y} A=0.5*d*b \bar{y}=0.25*d ===> Q=0.125d2b I=(b*d3)/12 τ=VQ/(Ib) τ=V*0.125d2b*12/((b2*d3) τ=1.5V/(bd) now d changes as a function...

I need to find the volume of this figure y=sinx, y=sinx + 2, x=4, x=-4 using the area of triangular cross sections. i don't really know where to start...how to find the formula for area of cross section etc. HELP!

in a given shaft with a circular cross section, the radius changes linearly find the maximum shear stress i used T*r/J and since J is dependant on r^4, i found that the cross section with the smallest radius will feel the largest stress. find the angle of twist at the end of the...

A 3.5 m long steel member with a W310 x 143 cross- section is subjected to 4.5KNm torque. Knowing that G=77GPa, determine (a) the maximum shearing stress along the line a-a, (b) the maximum shearing stress along the line b-b, (c) the angle of twist...

Hi guys, I would like to derive the Ixy equation from simple integration and I can't seem to get the right answer (third equation down the picture). I seem to be able to derive Ixx and Iyy easily but product moment of area requires first moment of area to be calculated and I just don't know...

Homework Statement Given the following magnetic circuit: It's constituted by two cores in serie. The first one has an average length of 40 cm and the second of 10 cm. Both are made of ferromagnetic material, which can be considered lineal and with \mur1 = 1000 for the first one, and \mur2...

I was calculating the cross section for a particular decay and saw that I was off by a factor of half from the known value.. Now, the decay has two identical particles in the final state and I seem to remember having read somewhere that this requires a factor of half...but I am not able to...

Homework Statement I am writing a formal lab lab report. I have trouble with Appendix section. I am going to put raw dat and sample calculation. And my question is, do I have to number them? For example, APPENDIX 1. raw date(chart) blah, blah blah... 2. sample calculation of...

The base of a solid is the triangular region bounded by the y-axis and the lines x + 2y = 4, x - 2y =4. Find the volume of the solid given that the cross sections perpendicular to the x-axis are isosceles right triangles with hypotenuse on the xy-plane. So what I did is: 2\int_{x=0}^2...

Hello I am reading this book: "[URL and the appearance of a classical word&f=false"]decoherence[/URL] I hope someone could help me. Please go to Appendix A1 Joos introduces the notation f(q,q'). What is the dimension of f from his notation? Next page he writes that \int f^2 d\Omega...

I recently rejected a code calculation because the flat head thickness on a 6" NPS Sch. 80 header was thought to be too thin. This calculation was for an unreinforced flat head per Section 1, PG-34 sketch g-1. The design has tubes that are within the distance of 2*sqrt(d*ts) and the value of m...

I am very new to LaTeX (outside of PF). I am trying to write up a basic Template to use as a reference. Most issues I have been able to find documentation for. However, I am haveing trouble finding this one. I am using \documentclass{article} and cannot seem to get my lines to indent within...

Hi For example in e-e- -> e-e- scattering (electron-electron scattering) the differential cross section goes to infinity as theta goes to zero. Consequently the cross section is infinite. But how can we measure and interpret the cross section/differential cross section and interpret it as a...

Hi I am a third year mechanical engineer, and have been reading around the course. I have never heard of the two methods above, and they have never been mentioned on the course - and therefore arent relevent, but I am reading an article that seems to use them. The following is what I have: It...

Does anybody know how to calculate cross section of the photodissociation of CH?

Hi all I found http://en.wikipedia.org/wiki/Cross_section_(physics)#Relation_to_the_S_matrix" on wikipedia: {d\sigma \over d\Omega} = (2\pi)^4 m_i m_f {p_f \over p_i} |T_{fi}|^2 Has it the dimension of a surface? (I only see M*M) It is the first time I read this formula about...

Hi! I have the following problem: Let P be a principal bundle over a manifold M, p: P -> M. Let G be the lie group acting on P from the right. Now let U be an open set on M and s : U -> P a smooth section. Now it has been said that we can define a local trivialization of P by t ...

I am reading some material on laser physics and quantum physics, there involes something called absorption cross section, collision cross section, differential cross section and so on quite often. I try to google the definition online but many website or book just give the formula instead of...

Here's the question: How can we describe a sudden change in the cross sectional area of a super conductor carying a current i from bigger A1 to smaller A2, such that the current density J after change is higher than Jc ? I have one scenario in my mind, the tempreture rises in the...

Directions: Let \phi: G \rightarrow G' be an isomorphism of a group <G, *> with a group <G', *'>. Write out a proof to convince a skeptic of the intuitive clear statement. Problem: 41.) If H is a subgroup of G, then \phi[H] = {\phi(h)| h \in H} is a subgroup of G'. That is, an...

Hi again everyone, I have some doubts about the path integral expressions given in Section 9.1 of Peskin and Schroeder (pg 281 and 282). For a Weyl ordered Hamiltonian H, the propagator has the form given by equation 9.11, which reads U(q_{0},q_{N};T) = \left(\prod_{i,k}\int dq_{k}^{i}\int...

Hello, I am curious about fusion reaction cross sections, and fusion power in general, and have been trying to self-teach myself in this area. I saw some emprical data for cross section curves in a paper that I read recently, and thought I understood enough of what made the curve (cross...

I know the formulas for the length and velocity forms of the photodetachment cross section for an electron with energy \hbar\omega are, respectively, \sigma_{L}(\omega)=\frac{4\pi^{2}\alpha a_{0}^{2}\omega}{3}\sum_{f}|\langle\Psi_{f}|\sum_{j=1}^{n}z_{j}|\Psi_{i}\rangle|^{2} and...

Is "Section Modulus" the same as a cross sections "bending strength modulus"? Good afternoon everyone, I am following an ECE directive that sets out the requirements for the properties of a "Rear underun protection device" for the rear of a lorry. It states that the underun bar must...

I am deisigning a pin jointed machine that uses some standard channel section. I am having difficulty getting consisitency with the channel section (type BS10279:2000 Hot Rolled Steel Channels) dimensions due to the wide nominal tolerances. Is anyone aware of any channel/U -Section that has...

Homework Statement Water flows at 3.64 L/s through a horizontal pipe that narrows smoothly from 10.2 cm diameter to 4.89 cm diameter. A pressure gauge in the narrow section reads 47.0 kPa. What is the reading of a pressure gauge in the wide section? Homework Equations F=PA P1+...

How to deal with non uniform cross section bending? How does one approach a solution for bending of a shaft having multiple diameters. I have one particular shaft in mind that has 11 diameters to get to the midpoint. I know the deflection at the midpoint, and I would like to calculate...

Hello everyone, I have a beam deflection problem. I haven’t looked at deflections for a while now and I can't understand why my solution is a million miles out fro the results I have seen through testing. Problem: I have a beam made from 100x40x3mm mild steel box section which is...

Homework Statement A uniformly charged, non-conducting, infinitely long cylinder of radius A is parallel to the z-axis, and its central axis intersects the x-y plane at the origin. It has a charge density p (C/m^3). Material is removed from the cylinder leaving a cylindrical void of radius...

Not technically homework, just something I wanted to see if I could do. Homework Statement Find the differential cross section for the interaction between an electron and a photon via compton scattering. Basically, I'm just after calculating the matrix (s-matrix?/amplitude?) for the s-channel...

Help! Vectors! Homework Statement In the triangle ABC, D divides AB in the ratio 3:2, E divides DC in the ratio 1:5 and F divides AC in the ratio 1:2. Show (using position vectors and the section formula) that B, E and F are collinear and find BE:EF Homework Equations Section...

Please Help! Easy conic section question! 1. Graph each equation. Identify the conic section and its lines of symmetry. Then find the domain and range. 2. x^2 - y^2 - 9 = 0 3. I have no idea how to do this. I know it's a hyperbola because i solved for "y" and graphed it in my...

Homework Statement The differential equation that models the volume of a raindrop is \frac{dy}{dt} = kv^{2/3} where k = 3^{2/3}(4 \pi)^{1/3} A) Why doesn't this equation satisfy the hypothesis of the Uniqueness Theroem? B) Give a physical interpertation of the fact that solution to this...

Homework Statement Show, using Fermat's principle, that perfect reflecting surfaces are conic sections. Homework Equations Equations for the ellipse, parabola and hyperbola The Attempt at a Solution Ok, the ellipse seems easy. All rays coming from one focus reflecting to the other...

Hi I have an m-file which accesses another m-file at some point, but I don't want it to run the entire file. Is there a way to skip the first and last 10 lines of the file? I could just create a new file with the code I need, but this is like an addon to a programme, so if I could leave the...

Homework Statement a rectangular box with no top is formed by cutting out equal squares from the corners of a square sheet of metal, 10 cm by 10cm, and bending up the 4 sides. What size of square must be removed from each corner to generate a box with a volume of 50cm^3? (Note: there are 2...