What is Beams: Definition and 274 Discussions

Hello Forum, Awhite background reflects all colors (i.e. all incident wavelengths). A black screen, being black, absorbs all incident types of light (i.e. absorbs all incident wavelengths). a)Let's consider a red monochromatic beam projected on a black screen inside a dark room. Would the...

If you have say, a 3 story building and each floor has I beams (with cross pieces) carrying the weight, would the beam holding up the second floor have to carry the load of the third floor as well? I don't think so (if I drew my FBD correctly, the largest reaction should be the one pushed up by...

Hi, I was looking at derivation of a multi gaussian beam to represent the ultrasonic beam from a transducer through a fluid. In the derivation a complex valued symmetrical 2x2 matrix is used whose imaginary part of eigen values is more than zero. Can someone please tell me what are the...

Hello this is my first post here so basically I've had my best crack at all the questions all I am really after is a bit or re assurance as to my answers and if any are wrong were I have gone wrong essentially. I've tried to include all my working out were possible. 1. Homework Statement The...

Hi there, I'm solving the equation for the transverse vibrations of a Euler-Bernoulli beam fixed at both ends and subject to axial loading. It's a similar problem to that described by Rao on page 355 of his book "Vibration of Continuous Systems" (Google books link), except the example he uses...

Hi there, I'm studying for an exam in mechanical vibrations, and I'm at the moment looking at longitudinal waves in continuous beams - and I've run into some problems. The whole idea is to explain the solutions of the system in terms of eigenvalues and eigenfunctions, which is not that big of...

Hi, I'm doing question (c)(ii) in the image below, full working is provided below: (c)(i) is 150kPa. I = bh^3/12 - 2 * bh^3/12 (0.25 * 0.256^3)/12 - (2* (0.119 * 0.22^3)/12) = 1.3831 x 10^-4 m^4 Q = y*A = 0.119 * 0.018 * 0.250 = 5.355 x 10^-4 m^3 shear force = (150000 * 5.355 x...

Hello, This is my first post and I have one question. My major is not physics. For now, I am struggling to understand general relativity for own reason because the math involved is troublesome to me but facing one question I need to figure out. It is related with the gravitational lensing...

Hi, normally when we try to analyse a structural beam with composite section, we apply transformed section method or so. But what if two beams are just put together (one onto another one) instead of having a composite relation (e.g. glued together), how am I going to analyse the forces and...

Regarding expansion, from the present to the past: Do light beams (generally) converge to a single point, in the remote past, as geometry and matter was also condensed to a single point, prior to the big bang? Thank you.

Homework Statement A uniform steel beam has a mass of 1000kg. On it is resting half of an IDENTICAL beam, on one side. The length of the beam is L. The block and its' smaller counterpart are being held up by two poles, one on each side of the larger beam. What is the vertical support force for...

The cross-section of a cost-iron beam is shown in figure below, the loading being in the plane of the web, the upper portion of the section being in compression. If the maximum permissible stresses are 2000 kg/ cm2 in tension and 3000 kg/ cm2 in compression, find the moment of resistance of the...

Hey guys! Supposedly I will need to design a floor with slab, beams and columns. Brickwall should rest on top of beam as possible. How about low wall, does it needs to rest on top of beams as well? Thanks! Harry.

Homework Statement In a youtube video() it is explained how gaussian beams propagate through an optical lens. Using the complex parameter q \frac{1}{q} = \frac{1}{R} - \frac{j\lambda}{\pi n w^2} (with R the radius of curvature), one can use the ABCD matrix to calculate the effect of an optical...

This is probably an impossible question to ask, but I feel bound to give it a try. Assuming a level of technological know-how that has enabled human beings to journey beyond the heliopause - if not to the nearest stars - just how far can it be reasonably supposed for message-bearing laser beams...

Does anyone have a good book on focussing laser beams? I'm working on a project and I want to know more about focussing high energy pulsed lasers, M^2 factor, top hat beam shapers, ray tracing and fiber optics. I've read Renk, Basics of Laser Physics but these subjects are only discussed very...

It has been my understanding when working with natural wood beams/joists, that for example, two 2x12 members over a 12' span gain significant strength when they are fastened (nailed, glued or both) together rather than just lying side by side touching one another. Is this phenomenon...

Hello When a beam* pass through a thin layer of material (some microns), at the exit some electrons are released; so a electron cloud is formed around the exit point of the beam. My question is: what is the energy distribution of these released electrons? (Maxwell, random,... ) I think they...

Homework Statement I need to find vertical reactions, sketch the shear force and bending moment diagrams, calculate bending moments, etc Homework Equations Please see my attached answer The Attempt at a Solution This is attached, I think my answers are correct, I just need help in...

How do two light beams combine at a shear angle? Two electromagnetic beams cross at a shear angle. They have equal phase, intensity and polarization. The angle is shear enough, so that in region in which they intersect, there is less than a quarter wave difference in phase over the...

I would like to figure out Mcr(elastic critical moment) and Mpl (Maximum plastic moment) in a beam due to buckling in abaqus. How to model material non linearity. How to model geometric imperfection (slightly crooked beams) Is there any way to import I section (rolled) profiles instead of...

I am trying to solve for the deflection and stress in a tapered beam (constant width b) shown in the attachment, and I am getting confused by at least 2 things: 1) how to deal with the "imposed" coordinate system, 2) the nonsymmetric shape and the corresponding neutral axis. [Assume that the...

Hey everyone, I was just wondering if someone could explain to me what Bending stress is? Supposed you have a cantilever beam with a point load at the free end, I know that the bending stress will decrease as you move away from the fixed end? but why? and how can you back that up? Also, as...

Hi this is my first post here. Sorry for this naive question xD I want to calculate antenna gain for which I need the horizontal Φ and vertical θ angle of an antenna beam. The formula for gain is. is it ok to convert the rectangular coordinates of antenna into spherical coordinates and compute...

Attached is my ANSYS model of a spring made using cantilever beams. In playing around with with different dimensions, I noticed that the longer I made the connecting section (dirty green section) the less of a total deflection there was. Could someone explain to me why this is? The overall goal...

The equation for shear stress as I know it is VQ/It where V is the shear force, Q is the first moment of area(?), I is moment of inertia and t is the length of the section in question. My question is, is there a general formula for Q? In my Solid Mechanics notes I've written that Q = ∫y.dA but...

hello! I don't understand, what is the equation that we use in beams is it that forces 1,2,3 equal with the reactions at the two supporting points? or the torques are 1,2,3 equal with the reactions at the two supporting points? and how do we find the reactions at the supporting points? thanks!

Homework Statement Light consisting of a mixture of red and blue light enters a 40°, 70°, 70° prism along a line parallel to the side opposite the 40° vertex. The index of refraction of the prism material for blue light is 1.530, and for red light it is 1.525. What is the angle between the two...

Ok I'm struggling with something here. I am rusty so have probably just misunderstood something simple mathematically. There are equations to create the Bending moment diagram for each different type of beam subject to a UDL; cantilever, simply supported, fully fixed ends etc. However I just...

Help needed In my course paperwork I can't seem to find the relevant equations needed to complete the following in if someone could help point me in the right direction of equations needed I would be very grateful 1. Homework Statement A rectangular hollow beam length of 3m is simply...

HELP! how to calc the force needed to bend this fixed beam channel by 4mm at 'F'http://www.engineersedge.com/engineering-forum/attachment.php?attachmentid=1254&stc=1

Homework Statement http://postimg.org/image/9va37id55/ The question is to find the shear stress at the points A, B and C. The solution uses the sectioning planes aa, bb and cc to do so. For example, at C, how should I know whether to use a horizontal or vertical sectioning plane. Also, how...

Homework Statement Two identical, uniform beams weighing 260 N each are connected at one end by a friction-less hinge. A light horizontal crossbar attached at the midpoints of the beams maintains an angle of 53 degrees between the beams. The beams are suspended from the ceiling by vertical...

How come relative velocity of the beams can be expressed by v_{12} = \left| \vec{v}_1 - \vec{v}_2 \right| = \left|\frac{\vec{p}_1}{E_1} - \frac{\vec{p}_2}{E_2}\right| where \vec{p}_{1,2} and E_{1,2} is the momenta and energies of incoming particles, respectively? Similar equation is in Peskin &...

I'm working on a problem involving steel structural members on the exterior of a building. I need to figure out how much insulation (for summer conditions) and possible heat tracing (for winter conditions) would be required to maintain minimum and maximum temperatures. I know I need to use the...

I came across this article was incredibly interested. I've read the paper and the material was completely over my head. What should I, with a high school level education and no background in optics, do to have a complete understanding of the topic discussed in the paper? What sciences would I...

When in a stern-gerlach electrons are not detected the two beams can merge behind. We just have to add the amplitudes. this is easy because up> and down> are orthogonal. Suppose that we have a POVM setup with 3 output channels: F1 F2 and F3 as operators. They sum to Id but have not to be...

Scientists have developed a new type of laser, called a polariton laser, which can be generated using 250x less power: http://www.eurekalert.org/pub_releases/2014-06/uom-anw060514.php Polariton beams are said to have properties of both matter and light, since polaritons are a combination...

any formulas to work out the section of the beam from the stress on it. thanks Gclark

Hi I am a HNC student an am having trouble with this question below... A universal I section beam is simply supported at each end and must withstand concentrated shear force of 240kN vertically downwards. if the maximum allowable shear stress in the beam is to be 65MkN/m^2 determine the...

Homework Statement Two laser beams, one of wavelength 633 nm and intensity I1 = 4.00x106 W/m2 with a circular beam profile D1 = 1.33 mm in diameter, and one of wavelength 442 nm and intensity I2 = 4.00x106 W/m2 with the same circular beam profile are fired, crossing at an angle of θ = 45°...

Homework Statement I need to find the total strain energy in the beam with a moment applied: The Attempt at a Solution For my attempt I decided to split the integral into two parts since the moment is different depending on whether or not you are on the left side of the moment or on...

Homework Statement If one light beam is heading toward you from the right, and another is heading toward you from the left, how quickly from the perspective of the right-moving beam is the left-moving beam approaching it? 1) 0 2) c 3) 1.5c 4) 2c Homework Equations (v+w) / (1 + cw/c2) The...

I'm trying to focus a 3mm diameter laser beam (527nm) to a 0.3mm spot size. According to this online calculator I need a +500mm focal length lens and a -50mm FL lens separated by 450mm. However, in practice this did not produce a focused spot. I'm assuming this calculator has made some...

depending on your frame of reference, correct? If I am standing still, and at the same time (my time) shine 2 flashlights in opposite directions, after one second on my watch, the leading edge of the light beams will be 372,000 miles away from each other. (186k miles to my left, and 186k miles...

Why is there a large Shapiro delay when a light beam passes a black hole? Coordinate velocity of the beam is slowed down in a gravity field, except for the straight down component of the coordinate velocity? Some part of the trip takes a long time anyway.

Do we presume the light beams to be parallel even though they meet at one place? like the image here http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/sinslit.html

Homework Statement So I have a beam here, I'll post a Photoshop diagram of the problem at the bottom of this section, but its an overhanging beam simply supported at one end, and mid way down another, points A and B. I've changed up the values so I can do my work myself, I don't want someone...

Hi, I don't know if anyone can help. I would like to be able to calculate the bending moment and deflection of a beam that is: Built in on both ends (no rotation) It has 2 different distributed loads not equ ispaced along the beam and has 2 point loads which are also not eqi spaced. I can...

Besides proton therapy: What are charged particle beams currently used for and what new uses could they have?.