Beams Definition and 274 Threads

I am having some conceptual difficulties here. Let's start with the electron-photon vertex piece of the QED Lagrangian: -e\overline{\psi}\gamma^\mu\psi A_\mu Now we can write this in the chiral representation as -e\overline{\psi}_L\sigma^\mu\psi_R A_\mu -...

What makes the three mechanical objects Truss members, beams, and frames having different characteristics related to force systems. Example truss members only exhibit tension and compressional forces, that's different from others.

My big problem here is with the geometry... Homework Statement I just took a picture of the problem. It's 15-10. http://img839.imageshack.us/img839/9712/optics.jpg Homework Equations n_1sin\theta_1=n_2sin\theta_2 n_{\bot}=1.6584 n_{Parallel}=1.4864 (I can't find the Parallel sign) The...

I am working on a design project and we have thought of cantilever beam to hold 1 ton mass spread along its span. I wanted to know what are popular ways to strengthen a cantilever beam to counter deflection and be able to hold objects loaded over it easily as I haven't seen any mechanics of...

Homework Statement I have been asked to provide a detailed reinforcement plan for a continuous beam. This beam has the following dimensions: h=180mm, b=500mm and l=5400mm. The supports are three and located at 200 (roller), 2700 (pinned) and 5200 (roller)mm, creating two equal spans. The...

Homework Statement In calculating stresses, how do we determine when we have a negative in front of the question and when we do not have it. I am really confused, meaning I have not understood the concept, but the examples I am looking at some have got σ= My/I whilst others have σ= -My/I...

hello all I have this problem to solve in ansys workbench 13 (Im new to this software): two parallel 5000mm length square beams in contact 200x80x8 (EN10219: structural hollow sections ) in frictionless contact and on the sides two side plates. At the ends I have two suports and I have on top...

Homework Statement This is the question i am asked: Determine a suitable size for the (gantry girder) beam selected from standard section tables. Prior to that is some information: The cross-section of the beam shows that of a Gantry Girder. The maximum bending stress in the girder...

Homework Statement estimate light, eletron, neutron beams energy to use 'order - of - magnitude' [eV] Homework Equations E = hv The Attempt at a Solution E = hv where h is Plancks constant and v is frequency and E is energy...

This might look a bit stupid but I have just started beams and I can't understand a part in this example it is to do with finding a general equation of the height at any given point on a tapered cantilever beam can someone please explain

If I combine 2 laser beams of different wavelengths, would I get a beat frequency of the difference between the 2 lasers? Thanks, Bill

I've got a situation where I'll be placing a load (a vacuum pump) on two separate beams. Basically, the pump attaches to a machine with a bolted flange. I'm wondering what would happen if we removed all the bolts except for the top and bottom one and let the pump hang...what the bending...

Homework Statement Hi guys, I need some help. I haven’t done mechanics for a few years and am a little rusty but have a task for work to verify FEA (which hasn’t been done yet). I have a semi circular beam that is bolted down on its ends. Mid way there is vertical force of 100kN...

Suppose you have two coherent microwave beams, one beam at 45 degrees to a reflecting wall and the other one at 90 degrees, with the two beams pointing to the same point on the wall. If the two beams are 180 degrees out of phase and destructively interfere at the point on the wall, will the...

Hi everyone, Recently I faced a problem in calculating bending stress in a long UPN profile "flange" due to concentrated force. It seems that the regular/familiar formula for bending stress in a finite/short element does not applicable in local bending of long/infinite beam. See sketch...

There is a classic result by Tolman, Ehrenfest, and Podolsky that in classical GR, the interaction between pencil beams of light is zero in the case where the beams are parallel, nonzero otherwise. (The case where they're not parallel can always be reduced to a case where they're antiparallel by...

Need to build a bridge 20 foot wide gully. The bridge is 4 ft wide and will be constructed of four by eight ft plywood sheet which is placed on top of 2 composite beams that are 4 ft apart (see link for picture).The 2 composite beams need to take all the load which is 500 lb/ft distributed over...

Homework Statement http://tinypic.com/r/2wbxm2s/7 This is a series of beams pinned together at A, B, C Find reactions at a b c Homework Equations Sum of moments at B has to = 0, sum of Fx = 0, sum of Fy = 0 The Attempt at a Solution Sum of moments about A, anti clockwise +ve...

Recently I have placed here the new - viable by my opinion Concept how to produce fusion. By some reasons I have decided not to file the patent application and so for discussing now I am placing here the description of Cyclic Reactor on base of that Concept. Ioseb (Joseph) Chikvashvili

Homework Statement Calculate the reaction forces at B and D See attached jpeg. The Attempt at a Solution sum of vertical forces By + Dy = 7 + (9*5) Do I then solve for the moment about D or A or B? for moment about D i have: -Dy -7 -(9*5)+9By+(12*2)=0 is this correct, please explain to...

Hi there Just a quick question; when I'm calculating moments in a cantilever beam (in my case a quarter circular one), is there any reason (apart from my own ineptitude) why I shouldn't be able to make the cut and FBD starting from the fixed end? I get different answers when I make the cut...

Hello friends, so i have this problem: A beam under test has a measured radius of curvature of 300 m. The bending moment applied to it is 8 Nm. The second moment of area is 8000 mm4. Calculate the modulus of elasticity for the material. ok so using the engineers bending equation i have...

I posted this as a part of a thread on the classical physics forums, but the doubt wasn't resolved, so I thought this might be a more appropriate place... A fixed beam is considered equivalent to a Simply supported beam (SSB) with a point load at its mid point(and thus having reactions Ra*...

Can someone explain what are the implications for the 13 neutron beams that have been observed at Fukushima? How are they created? What will cause more to be created?

Homework Statement 3. A laser scientist tells you that her He-Ne laser can be focused to a spot size of 5.00 microns. When pressed for details, she tells you that she got this number by measuring the Full Width Half Maximum (FWHM) of the intensity profile of the laser waist. a) What is...

I wish to dampen a boom arm, which at its fixed point is connected to a vehicle (arm length is 5m long). The boom is 'L shaped' is attached to the to of the vehicle and extends 5m in the horizontal, then the second leg hangs down 5m, almost to the ground. The end of the boom arms contains lead...

Hi! I didn't understand how the brewster angle works. Why do I have a polarised beam? Do I need electromagnetism to understand this?

Would General Relativity predict that two initially parallel light beams will converge due to their energy curving space-time? John

Can electricity be transmitted using Concentrated beams without using wires with no energy lost in the process?

Hello people, i have got a few thoughts which i would like to share. I few month ago i foundout that there are laser beams in the frequency range of of microwaves (maser beams). (http://en.wikipedia.org/wiki/Maser) I consider the following situation: If a conducting medium (lets think...

I'm teaching a class using Shigley's Mechanical Engineering Design. There is a section on deflection of curved members. If you have this text, you'll notice it calculates the strain energy in bending, axial, and shear, as usual. Then it says that there's another "negative" strain energy...

hi i would like to ask a question concerning the application of microwave beams. First: a microwave beam can be thought of as a laser beam but the light it emitts is in the frequency range of microwaves (see Maser)... I was wondering why such beams are not used for medical imaging...

Hi everyone, I am studying the feasibility of using the collision of two beams to obtain nuclear fusion energy. I would like you to recommend me some serious and intersting articles about this. Is there any experiment that does fusion by beam collitions already? Im open to hear about any...

Homework Statement calculate the position from A where the maximum deflection occurs. Your answer should be accurate to 3dp. You may assume IE= 100Mn Homework Equations I'm going to go with EI d2y/dx2 = m (the 2 are meant to be squared) The Attempt at a Solution Is this equation...

Hi. I can't understand one thing in mechanics. I am trying to learn how to solve beams in mchanics. I have a triangular load (a load which changes constantly). Why is the point of application of the net force in the one third of the triangle's base? While dividing a right triangle into...

Homework Statement Coherent light from a laser is split into two beams with intensities 16I0 and 2.25I0, respectively. What is the range of possible light intensities when the beams are recombined? Homework Equations A = sqrt(I)k; I = (A/k)^2 The Attempt at a Solution A1 = sqrt(16)k = 4k...

As of this point. I understand the following. 1. there is almost 90% loss when applied to a laser system. 100 watts in 10 watt beam out. 2. when a beam is split there is also a loss, (amount unknown) 3. if you take a 20 watt beam and (with not loss) split it in two and cross the beams...

Hi all, I have a problem with cantalever beams, the beam is 1m long by 0.1m by 0.1m. A 10Kn force placed at the end of the beam deflecting it down. My lecturer simmulated the problem in Ansys and we all got to do it with him using more dense nodes and solutions to find a more refined answer...

I have attached the original question and my attempt at the solution. I think I am on the right path but I am not sure. Can some one please direct me on if I am right so far and what to do if i am/ am not. Thanks

Greetings, Is there a way to combine multiple lasers beams to create a more powerful beam? If so, what optics are needed? How do they need to be arranged? Thanks

1. Hi all, I'm doing a simulation on 3 different cantilever beam as shown in the attached figure. a) is the beam with only width varying from the base to the free end (height stay constant along the beam) , b) is the beam height varying from the base to the free end (width stay constant along...

Does anyone know the spring constant for a clamped/fixed beam with length L that is uniformly loaded? I know the spring constant for a clamped beam that is centrally load by a point load is k= 192EI/L^3 I know for a uniformly distributed is different.

Hallo I have been thinking about when beam starts to behave like string. My questions are: How much tension do you need to put on a beam before it starts to behave like a string? And when does the behaviour become purely string like? Thanks

how fast are the particles in the 2 beams of a Pulsar traveling? and what happens when two of those beams intersect? do those particles collide at extremely high velocities like in particle accelerators?

It has been a few years since I have done beam analysis, and I really don’t remember how to solve this type of problem so I have been reading up on it. I have found similar situations but nothing that matches the problem I am having. I have a continuous beam of 3 spans with a uniform...

With two electrons emitted from a decaying atom in opposite directions, the speed can easily be greater than the speed of light between the two electrons (e.g. 0.7c in each direction). If two receivers then pick up the electrons, hasn't the information traveled between the two receivers at a...

Can someone explain to me how two parallel electron beams can be attracted to each other according to special relativity. Classical physics says each beam will generate a magnetic field so the beams will be attracted to each other. Relativity says the magnetic field only exists for observers...

Hey Guys, first of all I apologise if this question is posted in the wrong forum section and a mod has to move it to its correct location. I am trying to find information on combining the paths of several laser beams. I have found much complex information pertaining to the combination of the...

Homework Statement An electromagnetic wave in a vacuum /w magnetic field of 265 mG. If the wave is spatially confined to a beam with a diameter of .75mm, how much energy is measured by a photodetector with an active area with diameter 5 cm in one second. The Attempt at a Solution...

Two parallel beams of light going opposite ways pass each other. What speed do they pass at? I'm told they pass at the speed of light? How is that possible, I know in relational math you would add the two speeds but for light it is different right? What math does it use?