What is Barrier: Definition and 260 Discussions

Traffic barriers (sometimes called Armco barriers, also known in North America as guardrails or guard rails and in Britain as crash barriers) keep vehicles within their roadway and prevent them from colliding with dangerous obstacles such as boulders, sign supports, trees, bridge abutments, buildings, walls, and large storm drains, or from traversing steep (non-recoverable) slopes or entering deep water. They are also installed within medians of divided highways to prevent errant vehicles from entering the opposing carriageway of traffic and help to reduce head-on collisions. Some of these barriers, designed to be struck from either side, are called median barriers. Traffic barriers can also be used to protect vulnerable areas like school yards, pedestrian zones, and fuel tanks from errant vehicles.
While barriers are normally designed to minimize injury to vehicle occupants, injuries do occur in collisions with traffic barriers. They should only be installed where a collision with the barrier is likely to be less severe than a collision with the hazard behind it. Where possible, it is preferable to remove, relocate or modify a hazard, rather than shield it with a barrier.To make sure they are safe and effective, traffic barriers undergo extensive simulated and full scale crash testing before they are approved for general use. While crash testing cannot replicate every potential manner of impact, testing programs are designed to determine the performance limits of traffic barriers and provide an adequate level of protection to road users.

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  1. FOIWATER

    2nd order approx. of barrier function

    Homework Statement write the 2nd order taylor series for the log barrier function $$-\sum_{i=1}^{m}(b_{i}-a_{i}^{T}x)$$ Homework Equations See Above The Attempt at a Solution Here is my attempt at a solution $$\nabla...
  2. nilesh_pat

    Causes for producing Sound while crossing sound barrier

    What causes to produce sound (like boom) when crossing a sound barrier. With regards Nilesh.
  3. ryanuser

    What is a Schottky barrier or contact?

    I looked at many websites including wikipedia and videos on youtube but I found them all very complicated and many contained diagrams that did not make sense to me. What is a Schottky barrier or contact in simplest form so that a 17 year old high school physics student can understand? Thanks
  4. D

    Particle waves through a potential barrier

    Hi all, I came across this figure in a textbook. Simple stuff, but can get tricky: I don't understand why the sign convention flips upon entering the barrier (region II), but I guess the book is correct and that I should just take it as a fact. If anybody has a reasonable thought to add...
  5. L

    Understanding the Peierls-Nabarro Barrier: Explanation and References

    I can not find what is exactly Peierls-Nabarro barrier? Could you gave me some explanation or reference. Everything I found are just different papers which I can not understand.
  6. R

    What happens if the new ARX bullet breaks the sound barrier?

    The venturi effect of the new ARX bullet almost doubles side exit velocity. What happens if the exit velocity exceeds the sound barrier in a fluid like a gelatin block?
  7. T

    Measuring Voltage Across the Blood-Brain Barrier: Is the Dermis a Barrier?

    Is there a way to measure the amount of voltage used when transmitting from the blood brain barrier to a particular muscle outside of the skin or is the dermis too thick?
  8. mcpaddler

    Velocity to knock over a barrier

    I have a problem of a vehicle that impacts a barrier and knocks it over. At what minimum velocity does the barrier tip? (assuming it did not slide and there is no damage absorbing energy in the collision), sort like Barrier 2 ft wide, 2 ft tall, 6 ft long, 3600 lbs. Vehicle 2000 lbs, bumper...
  9. D

    Surface Barrier in Type 2 Superconductors

    If a field line is moved into a superconductor it meets resistance. This resistance is modeled by adding an image flux thread outside the superconductor which then attracts the flux thread being moved into the superconductor. Why is this attractive force an accurate model of the resistance a...
  10. C

    Determining semiconductor type of Schottky barrier using IV

    I was wondering if it would be possible to determine if a Schottky diode was n-type of p-type (in the bulk) by only using I-V measurements?
  11. R

    Square Hill Barrier, weird question wording

    Homework Statement Consider a square hill barrier produced by a 10V potential. Incident upon this barrier is a steady stream of 5eV electrons. (a) If half the electrons are transmitted, how thick is the barrier? (Please derive the transmission probability rather than merely quoting it.)...
  12. Joy Prakash Das

    Wave function for a potential barrier

    Suppose I have a region from 0 to L. I have a barrier potential V from x1 to x2, such that 0<x1<x2<L. The potential is 0 everywhere. I have obtained the wave-function by considering the propagation from left to right. Now if I consider the propagation from right to left should I get a different...
  13. B

    Transmission Coefficient for Quantum Barrier

    Homework Statement Picture of Problem: Homework Equations $$\psi(x) = A_n e^{ikx} + B_n e^{-ikx}$$ for n=1,2,3 The Attempt at a Solution I know i need to relate the wave functions $$A_n e^{ikx} + B_n e^{-ikx}$$ for n=1,2,3 (the three areas of the barrier - before barrier, inside barrier...
  14. M

    Starlite and thermal barrier fun

    Hello everyone, First up, I know nothing about physics or chemistry. That out of the way, let's begin. I recently read about a very interesting material called Starlite which is supposedly a remarkable thermal barrier but is presumed lost to the world because the inventor kept the formula...
  15. P

    Understanding Diode Barrier Potential and Its Role in PN Junction Diodes

    Hi, For a PN junction diode, am I correct in thinking that the barrier potential (due to depletion region and hole-electron recombination etc.) is the same as the 'forward voltage' quoted on datasheets? Also, when a forward bias condition is created and the applied voltage is greater than the...
  16. X

    What is potential barrier against the photon penetration

    It is known that the penetration depth of photon into a material depends on the energy of the photon, density and atomic number of the material; because the photon energy is normally smaller than the potential against the penetration of photon, which is the potential barrier, so the incident...
  17. M

    Formation of Excimer Structures: Explained for Engineers

    Reposting from another section... Can anyone explain to me how an excimer is formed? Like structure wise? Considering Xenon. I've gathered that an excited state Xe*, ground state Xe, and a 3rd body M react resulting in an Xe* excimer + M(carrying away excess energy). I'm struggling to find...
  18. G

    Rectangular Potential Barrier Boundary Conditions with E=V

    Homework Statement I am trying to calculate the transmission and reflection coefficients for rectangular finite potential barrier between (-a, a) for a particle of mass m with energy equal to the height of the barrier (E = V0 > 0). Homework Equations...
  19. M

    Discrepency in using Schottky barrier

    As we know that in a metal-semiconductor junction schottky barrier arise. My question is that this is generally represented as sudden discontinuous jump in energies of conduction band on either side. But this will mean that the electric field at that point is infinite since electric field is...
  20. S

    Exploring Barrier Tunneling in Quantum Mechanics

    Barrier tunneling happens when, let say, an electron tunnels through a region when it has lower energy compared to the energy of the region (potential barrier). What differs Quantum from classical mechanics is that CM states the electron will never be able to penetrate the potential barrier...
  21. K

    Quantum physics potential barrier R and T

    Homework Statement Prove (6-44) which expresses the reflection and transmission coefficients in terms of the ratio E/V0.Homework Equations [/B] The Attempt at a Solution express k1 and k2 in terms of V/E? [/B]
  22. C

    Engineering Dynamics - Car Striking a Barrier

    Homework Statement A car, assumed to be rigid and having a mass of 800 kg, strikes a barrel-barrier installation without the driver applying the brakes. From experiments the magnitude of the force of resistance F_r, created by deforming the barrels successive, is shown as a function of the...
  23. N

    At how many rpms will a blade tip break the sound barrier

    Homework Statement The windmill is 400 feet tall and each of it's three blades are 130 feet long. At how many rpms will a blade tip break the sound barrier? Speed of sound: 1125ft/sec Homework Equations Linear speed: v = rω Angular speed: ω = Θ/Time The Attempt at a Solution...
  24. F

    Understanding Schottky Barrier Height: Why the Energy Bands?

    I have been chewing up some time ago the Schottky-Mott theory of Schottky Barrier height (which ignores the surface states). All the deduction seems to ground on fundamental thermodynamical principles (as the equality of Fermi levels- i.e. equality of chemical potential in equilibrium) but there...
  25. ranju

    Barrier Potential: Explaining the Contradiction

    The equation for the barrier potential is as follows: Vb = Vt loge(Na*Nd/square(n)) mV where Vt=KT/e This equation shows that the barrier potential is directly proportional to the temperature. So as temperature increases the barrier potential should increase. But in contradiction to...
  26. kq6up

    Delta Function Potential Barrier

    Homework Statement Background: The problem is to find the uncertainty relationship for the wave equation for a delta function potential barrier where ##V(x)=\alpha\delta(x)##. Check the uncertainty principle for the wave function in Equation 2.129 Hint: Calculating ##\left< p^2 \right> ##...
  27. A

    Double slit barrier questions

    I have some questions about double slit experiment. 1) Sometimes photons or electrons should bounce off the initial barrier and nothing should be detected in the plate. ¿Is this correct? i find a video saying that NOTHING is detected in the barrier, only in the plate. 2) If we put 1...
  28. J

    Potential Barrier for different types of junctions

    Hi all, How I can calculate the Potential Barrier when we have a metal- semiconductor, metal- metal, or p-n junction ? Can I calculate the Potential Barrier by using a workfuncion?
  29. C

    Infinite square well with barrier in the middle

    Homework Statement Show that the energy levels of a double square well V_{S}(x)= \begin{cases} \infty, & \left|x\right|>b\\ 0, & a<\left|x\right|<b\\ \infty, & \left|x\right|<a \end{cases} are doubly degenerate. (Done) Now suppose that the barrier between -a and a is very high, but finite...
  30. L

    Potential barrier. Schroedinger equation.

    Homework Statement Schroedinger equation for potential barrier. What if ##V_0=E## First region. Particles are free. ##\psi_1(x)=Ae^{ikx}+Be^{-ikx}## In third region ##\psi_3(x)=Ce^{ikx}##Homework Equations ##\frac{d^2\psi}{dx^2}+\frac{2m}{\hbar^2}(V_0-E)\psi=0## where ##V_0## is height of...
  31. S

    Energy for moving mass up a centrifugal gravity barrier

    Hi, I have been pondering on this - what is the energy required to move a point mass m0 from a radial position R to the center of a rotating frame, if the linear velocity v of the point mass at position R is relativistic (close to c). For an observer in the rotating frame, it should seem as...
  32. B

    Approximate transmission coefficient of a square barrier

    Homework Statement Two conductors are separated by an insulator. Model the insulator as a square barrier of height 0.01 keV and a width of 5nm. Determine the transmission coefficients for electrons of 7,000 meV. The only thing is I have to use the approximation formula for finding the...
  33. R

    Help with Potential Barrier question

    I have always understood (As well as I can) potential barrier questions, but this one has stumped me, and I was hoping someone could point out where my thinking has gone wrong. The wave function of an electron of mass m incident to the step from x = -∞ with energy E < V is = eikx + ρe-ikx for...
  34. S

    Tunneling from Rectangular barrier - Exponential Decay ?

    Tunneling from Rectangular barrier - Exponential Decay ?? Consider the Rectangular Potential Barrier. If one solves bound state Problem in this case, wavefunctions of Exponentially Decaying and rising kind are found for the Region in the Barrier. ψ = A eαx + B e-αx Yet Most Books and...
  35. P

    How to find barrier potential of pn junction diode

    I want to know that when a pn junction diode is formed and barrier potential is setup then how can we determine the same theoretically. Also I wan to know that is there any relation between barrier potential and energy band gapSmall band gap small barrier? ?
  36. M

    Electron tunneling barrier in DFT

    Hello all, I'm getting confusing about what to consider as a barrier for electron tunneling in DFT. What I'm doing is looking at the xy plane averaged effective potential, i.e. the potential that electrons feel. This potential in PAW formalism is composed of three terms: VHartree+Vxc+Vbar...
  37. M

    Solving Schrod. Eqn. for Potential Barrier with E > V

    I have a question that's driving me insane and I'm sure there's a simple answer that I'm missing for some reason, but I'm not getting my a-ha moment. Consider 2 cases from intro QM: Infinite square well Potential barrier with E > V0 For the infinite square well, the Schrodinger eqn...
  38. G

    Probability that the electron will pass through the barrier?

    Homework Statement An electron of energy E = 2.2 eV is incident on a barrier of width L = 0.7 nm and height Vo = 3.2 eV as shown in the figure below. (The figure is not drawn to scale.) What is the probability that the electron will pass through the barrier? The transmission probability...
  39. H

    Number of standing waves in a potential barrier

    Homework Statement Consider a resonant tunneling diode structure (attached image). This shows 2 AIAs barriers of height 1.2 eV and width t = 2.4 nm, enclosing a well of width L = 4.4 nm. If the effective mass of the electron is taken as 0.9 times the free electron mass how many separate...
  40. H

    Possible Rectangular Potential Barrier Transmission Problem

    1. The Problem Statement An electron of effective mass m* = 0.2me and energy E = 0.1 eV hits a barrier of height 0.4 eV and width t = 5 nm. What is the probability of transmission through the barrier? Use the simplest estimate which is an exponential function. Homework Equations I think...
  41. K

    Radiant barrier - surface geometry

    Hello, first post, don't know if I got the section right tough.. Basically I was wondering, if the efficiency of radiant barrier (for home insulation or industrial, high T) could be improved with different surface geometry eg wavy, triangular, pyramids? Why I'm wondering - the reflective...
  42. W

    Direct collision with a barrier at an angle

    Homework Statement A ball of mass m moves horizontally with speed 20 m/s towards a smooth barrier xy which makes an angle tan-inverse(4/3) with the horizontal.The coefficient of restitution is (3/4) find (i) The speed of the ball after the impact (ii) The magnitude of the impulse due to...
  43. G

    Schottky Barrier: Effects of Semiconductor Width on Contact Potential

    Hello Everyone, We know how a schottky barrier forms with a depletion region of width 'W' and contact potential 'qV' as shown in below figure, http://homepage.ntlworld.com/beehive77/images/ntypeschottky.jpg The depletion width 'W' depends mainly on doping concentration of the...
  44. Z

    Eigenfunction & Potential Barrier

    Homework Statement A particle of total energy E is incident on a potential barrier V0 (E<V0) between x=0 and x=a. Write down the allowed eigenfunctions in the regions x<0, 0<x<a and x>a in terms of five unknown constants A, B, C, D and F where A and F are the amplitudes of the incident and...
  45. B

    Scattering from finite square barrier

    Homework Statement Use the boundary conditions to show that \frac{A+B}{A-B}=\frac{k_1}{k_2}\frac{C+D}{C-D}=\frac{k^2_1}{k^2_2} Homework Equations A+B=C+D and k_{1}A- k_{1}B = k_{2}C- k_{2}D C e^{i k_{2}L}+D e^{- ik_{2}L} = F e^{i k_{1}L} and k_{2}C e^{ ik_{2}L}- k_{2}D e^{-i...
  46. T

    Resonant Frequency of Open Ended Pipes with a Barrier Imposed

    I was just wondering if anyone here had any experience with an open pipe system with a barrier imposed. Basically, say for a pipe open at both ends, at one end we place a barrier a distance away from the pipe. How would this affect the resonant frequency of the pipe? From experimentation...
  47. N

    How does the material of an obstacle affect a plane's ability to overcome it?

    It isn't classic homework with classic task or only theory. It is a interesting example of my friend. So, I think it is good to gave it there... I do not understand this very much, I prefer to astronomy, but I am interested it. Can a plane before a barrier (as shown) and stay put when the...
  48. A

    Alpha decay potential barrier.

    Homework Statement A nuclei of a atomic number Z decays into a alpha particle (a He nucleus with Z =2) and a daughter nucleus with (Z_{d}). The decay may be described as the tunneling of an alpha-particle through a barrier caused by the Coulomb potential between the daughter and the...
  49. C

    Does matter break the light speed barrier after the event horizon?

    This is a question someone asked me today and it's bugging me allot. If the acceleration caused by gravity is greater than the speed of light at a black hole event horizon then does this mean that the matter is falling at faster than light speed?
  50. dexterdev

    Conceptual difference between potential barrier & potential difference

    Hi PF, What is the conceptual difference between potential barrier and potential difference? both have an electric field associated with it. so is potential barrier a sort of potential difference itself and will it cause current flow in a closed circuit like diode shorted. Also why cannot we...
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