What is Wall: Definition and 756 Discussions

A wall is a structure and a surface that defines an area; carries a load; provides security, shelter, or soundproofing; or, is decorative. There are many kinds of walls, including:

Walls in buildings that form a fundamental part of the superstructure or separate interior rooms, sometimes for fire safety
Glass walls (a wall in which the primary structure is made of glass; does not include openings within walls that have glass coverings: these are windows)
Border barriers between countries
Brick walls
Defensive walls in fortifications
Permanent, solid fences
Retaining walls, which hold back dirt, stone, water, or noise sound
Stone walls
Walls that protect from oceans (seawalls) or rivers (levees)

View More On Wikipedia.org
Recent contents Top users
  1. R

    Does a particle have negative kinetic energy in delta function wall

    E is finite and V is infinite, So T should be negative infinite
  2. K

    Finding Normal Reaction and Friction Force on a Ladder Leaning Against a Wall

    Hi all, this is a problem with which I led myself in circles with for hours, because I kept forgetting to factor in a different thing each time. Long story short, I thought I'd cracked it, but my answer and the given answer are out by a square. Please see my efforts below! Homework Statement...
  3. M

    Velocity Calculation - ball bouncing off a wall at an angle

    Velocity Calculation -- ball bouncing off a wall at an angle Question: "A ball is locked at 45 degrees towards a wall at 4 m/s. It bounces away from the wall at an angle of 45 degrees at 3 m/s. Find the change in velocity of the ball at the bounce." My attempt: So I know that change in...
  4. J

    How to solve a problem with a bar laying against a wall

    Ok, so I have completely *solved* this problem. What I mean is that I have attached the problem in a photo, and my work in a separate photo. My first answer was 62.2° and I did not round at all, I left all of the answers in my calculator. I rounded some on the second time through and got my...
  5. rogerk8

    Why isn't it possible to walk thru a wall?

    Hi! If the atom is mostly empty space, why isn't it possible to walk thru a wall? The science documentary I saw the other day told me that if you where in a church, the nucleus itself would be represented by a fly on the floor while the electrons would be encircling the church cealing...
  6. N

    Co-efficient of friction of a uniform ladder leaned on rough wall

    Homework Statement A uniform ladder of weight (W) is leaned across a rough wall and on a rough floor. The reaction at the wall is (S) with frictional force (G)(upward direction) while the reaction at the floor is (R) with frictional force (F)(away from the wall direction). Frictional forces...
  7. C

    When does perseverance fail in learning mathematics?

    When do you hit "the wall"? Hey all, I am currently in my first year of undergraduate degree on a software development BSc and am studying a quite introductory mathematics course which effectively only goes up to higher algebra and trig/geometry. Most of the course is self taught from...
  8. V

    Does Sound Undergo a Phase Shift When Reflected From a Wall?

    Hello When a mechanical wave gets reflected from a rigid surface,say a fixed end of a rope ,it undergoes a phase shift of ∏ ,but when a sound wave gets reflected from a hard surface ,say from a wall,it doesn't undergo any phase shift . There is confusion regarding phase shift of sound wave...
  9. Q

    Why are only certain wavelengths reflected when light strikes a wall?

    This is my first forum post so I apologize in advance if I do not provide enough detail, speak clearly enough, or violate some forum etiquette. I have a few questions here all relating to the same thing so hopefully this isn't worded poorly or too much. When light strikes a surface, the...
  10. A

    What is the correct expression for the entropy of a gas with a potential wall?

    Homework Statement See the attached picture Homework Equations The equations given should be the relevant ones. The Attempt at a Solution I feel I got a bad intuition and understanding of this problem. I could eliminate T in favor of S and then express x and T by U and S. Is this...
  11. A

    Solving Ball's Wall Impact Time w/Force & Mass

    Homework Statement A ball is being pulled by a force given by ##F=kv^2##. Where "k" already includes the mass of the ball. After 10m it will run into a wall. The initial speed is 1m/s and there are no other forces involved. How much time does it take for the ball to hit the wall? Homework...
  12. G

    Change in momentum after hitting a wall

    Homework Statement 32) The change in momentum, in kg m/s, that occurs when a 1.0 kg ball traveling at 4.0 m/s strikes a wall and bounces back at 2.0 m/s is A) 2. B) 4. C) 6. D) 8. Answer: C Homework Equations Momentum==Mass*Velocity The Attempt at a Solution I get...
  13. S

    Help a chair leaning 60 degrees against a wall

    Homework Statement Hi guys, I have a problem here. A man is sitting on a chair leaning at 60 degrees against a friction-less wall. The height of the chair is 1.20 meters and the distance between the man's center of mass and the wall is 0.5 meters. The distance between the guy's...
  14. F

    Forces and water pressure on a wall

    Homework Statement I have a wall, which is basically a gate of a shipping lock. I have different water levels on both side of the wall. I made a graph to illustrate my problem and dimensions: https://dl.dropboxusercontent.com/u/47965009/problem1.png Homework Equations 1. Find the...
  15. I

    Shear Flow Against a Wall (Fluid Mechanics)

    Homework Statement Assume a shear flow against a wall, given by U= Uo (2y/ax - y^2/((ax)^2) where a is a constant. Derive the velocity component V (x; y) assuming incompressibility. Homework Equations Haven't been able to find any in my course notes. The Attempt at a Solution...
  16. K

    To find out if the ball goes over the wall, you need to

    Homework Statement You are kicking a ball in the air that is sitting on the ground. You are told the initial velocity and the distance to a wall of a known height. To find out if the ball goes over the wall, you need to A) determine if the ball is going up or down when it reaches the...
  17. P

    A book is pushed against a vertical wall at an angle

    Homework Statement Albert is pushing a 1.8 kg book against a vertical wall at an angle of 30.0 degrees. If the coefficient of static friction is 0.47 and kinetic friction is 0.35, how hard does Albert need to push the book to allow it to slide down the wall at a constant speed? Homework...
  18. Saitama

    Sound waves - Detector and a moving wall

    Homework Statement A sound source, detector and a movable wall are arranged as shown in the figure. In this arrangement detector is detecting the maximum intensity. If the speed of sound is 330 m/s in air and frequency of source is 600 Hz, then find the distance by which the wall should be...
  19. S

    Relation of cylinder wall pressure and flow inside

    What is the relation between the pressure that is exerted on the internal walls of a cylinder and the characteristics of a flow of water running inside it? Let's assume that the flow velocity is constant and that we have an inviscid flow of pipe flow type. Furthermore let's assume that the...
  20. N

    What was the average force exerted by the wall on the ball during the collision?

    Homework Statement Above you had a ball traveling horizontally at 25.0 m/s bouncing off a brick wall and rebounding at 20.0 m/s. The ball was in contact with the wall for 3.50 ms, and you found the magnitude of the average acceleration during the time the ball was in contact with the wall...
  21. M

    Biology - why do plants and algal have cell wall?

    Homework Statement Suggest a hypothesis to explain why algal and plant cells have cell walls. Suppose that mutant individuals from each group lacked a cell wall. How could you use these individuals to test your hypothesis? Homework Equations There aren't really... The Attempt at...
  22. X

    Shadow on Wall: Light Blur from Wave or Quantum?

    Hello, As we know, if one turn a light blub(and no other light is present) on and put his hand in front of a wall to make a shadow, the shadow is blurry, depending on the distance between the hand and the wall. I want to ask you if this blur is caused by quantum uncertenty (like this...
  23. S

    MHB Finding Inclination of Rod on Cylinder to Wall

    A smooth circular cylinder of radius b is fixed parallel to a smooth vertical wall with its axis horizontal at distance c from the wall. A smooth uniform heavy rod of length 2a rests on the cylinder with one end on the wall in a vertical plane perpendicular to the wall. Show that its inclination...
  24. R

    Static equilibrium against a wall

    Homework Statement A uniform strut of length, L and weight 780 N is free to pivot about point P where it is attached to the wall (see diagram) A weight W = 815 N hangs straight down from the end of the strut. A rope is attached to the same end as the load and the wall completes the support as...
  25. J

    Circular Motion and Static Friction Problem The Wall of Death ride

    Circular Motion and Static Friction Problem.. "The Wall of Death" ride Homework Statement A fairground ride called "The Wall of Death" consists of a cylindrical container of internal diameter 6.50m, mounted on a cylindrical axis. The passengers feel as if they are being pushed against the...
  26. F

    Frictional force on a block held against a vertical wall

    [b]1. A 5kg block is held at rest against a vertical wall by a horizontal force of 100 Newtons. 1-What is the frictional force exerted by the wall on the block 2-What is the minimum horizontal force needed to prevent the block from falling if the static coefficient of friction between the wall...
  27. J

    Statics, beam attached to a wall, reaction forces

    Homework Statement I´ll show it with a picture: Homework Equations Static equilibrium, Sum Forces=0 ; Sum Moments= 0 The Attempt at a Solution With the Fx, and Fy equations I can calculate the reactions Rx and Ry but I don´t understand the moments equation: Sum M around...
  28. F

    Fix Paint Damage After Removing Foam: Tips & Advice

    A lot of you seem like the "handy" type so maybe you can give me some advice. A friend of my had some acoustic foam on his wall (with spray-on adhere stuff), removed the foam, and now some foam is stuck and in other spots some of the paint was removed. 1. How should I remove the remaining...
  29. M

    Thin wall Pressure Vessel(cylinder)

    cylindrical pressure vessel with inner pressure P. Take a infinitesimal cube on the inner-wall of the vessel. When calculating the normal stress along the radial direction it is assumed that that it is equal to P on the both the negative \widehat{r} and positive \widehat{r} directions...
  30. N

    Amazing Galactic Wall Graphics

    Came across some rather [to me] incredible views of some large scale structures our universe...Check out the large graphic here: http://en.wikipedia.org/wiki/Galaxy_filament and if interested, also click on the additional illustrations just below...
  31. N

    Medical Anyone know where you can order free medical posters for the wall?

    Longtime lurker here. I want to put some science posters on the wall, but am not sure which firms send these out for free. I'm talking about the posters with some sort of diagram or schematic, in color. I've only found one organisation that sends them out. And I'll only name it if...
  32. M

    Max. Applied force on outside wall of spinning drum

    I have a 36" OD aluminum drum within another 48" OD aluminum drum creating 6” channel between the two diameters. The total height of the drum assembly is 16” This design project that I am working on requires me to fill this channel up with 12” of water which equates to about 342.5 lbs of water...
  33. A

    Melting a snowball by throwing it at a wall

    Homework Statement You throw a snowball at 0.0 Celsius at a brick wall. If you want it to melt completely, how fast will you have to throw it? Homework Equations Q = mL E_k = \frac{1}{2} mv^2 The Attempt at a Solution I initially reasoned that you would use Q = mL to find the energy...
  34. J

    Projectile Motion word problem from Calc III course (finding height of a wall).

    The problem is from the MIT Open CourseWare Calculus eBook by Strang. Chapter 12.2, #3: A ball is thrown at 60 degrees with initial velocity of 20m/sec to clear a wall 2m high. How far away is the wall? Finding flight time T, range R, and max height Y(max) is the easy part. How do I find...
  35. J

    Do sound waves get bigger when they bounce off a wall?

    Homework Statement The questions states, "If you speak while standing in a corner with your face toward the wall, you will sometimes notice that your voice sounds unusually loud. Explain."The Attempt at a Solution Is this because the sound waves are bunched up when they bounce off the corner...
  36. P

    Using Projectile motion to find the distance above a wall

    1. Homework Statement During a tennis match, a player serves the ball at a speed s, with the center of the ball leaving the racquet at angle θ below the horizontal at a height y0. The net is a distance d away and has a height h. When the ball is directly over the net, what is the distance...
  37. PhizKid

    Moving wall and ball collision

    Homework Statement I'm only interested in the second part where V << v Homework Equations Energy The Attempt at a Solution First I boosted to the frame of the moving wall to find the change in velocity of the ball after a collision with it. In the frame of the moving wall...
  38. D

    How many hydraulic rams do I need to prevent wall collapsing ?

    Homework Statement rectangle wall with 3m height, 20 length, 6.0m width. Rectangle filled with water. The Attempt at a Solution I've calculated the force acting on the wall to be: 1766 KN I have a hydraulic ram exerting 5 tonnes of pressure. How many do I need ...
  39. E

    Reaction Force On Ladder and Wall Case

    Homework Statement https://dl.dropbox.com/u/63664351/Physics/MECH1.PNG Homework Equations Sum of Forces and Torque = 0 The Attempt at a Solution I found similar problem here: http://farside.ph.utexas.edu/teaching/301/lectures/node133.html Why is there no vertical reaction on a...
  40. P

    A Cylinder Rolling Down a Vertical Wall

    Hello, this is not really a homework question, but a question on a specific problem so I thought it belonged here rather than the General Physics subforum. This is a problem that was asked in our final exam, and I have doubts about it's "correct" solution. Here's a paint art to explain the...
  41. H

    The force of wind blowing on a wall at an angle

    Homework Statement Say there is a wall with width w meters and height h meters. There is a wind with velocity v m/s blowing on the wall at a 45 degree angle. The collisions of the air molecules with the wall are perfectly elastic. What is the magnitude of the force on the wall? (The density...
  42. S

    Avoiding a Wall with Circular Motion: A Physics Exercise

    Should the driver apply brakes or turn the car in a circle of radius 'r' to avoid hitting the wall? This question is in the excercise of circular motion chapter. In this question I don't uderstand from where to start. Some help would be greatly appreciated.
  43. T

    Newton's Cradles vs Ball Bouncing off Wall

    Hello everyone! I was just reading about the working of Newton's Cradles and ended up having some confusion. When a ball is taken to a certain height and dropped, it comes down and hits the next ball. Now the explanation as to why the first ball stops and doesn't bounce back is attributed...
  44. G

    Two Masses Connected by Spring Against Wall

    Homework Statement A system consists of two blocks each of mass M, connected by a spring of force constant k. The system is initially shoved against a wall so that the spring is compressed a distance D from its original uncompressed length. Floor is frictionless. The system is now released...
  45. G

    Using a wall wart to replace batteries

    I have this dc heli called protocol. It charges from the remote which uses 6 aa batteries. So I got a 9 V wall wart. There's a couple problems with the wallwart when I used my analog multimeter to read the voltage it was reading 60 V. When I measured the batteries in the remote ball the remote...
  46. Darth Frodo

    Calculating Heat Transfer in a Cavity Block Wall with Windows

    Homework Statement A cavity block wall of area 10m2 constructed of 100 mm concrete, 50 mm air gap, 50 mm of polystyrene and a second 100 mm wall of concrete. The wall contains three windows with dimensions of 0.5 m x 0.7 m with glass 4 mm thick. The outside temperature is 5 °c and the inside...
  47. D

    Confused by "mv^2/L" - Average Force on Wall in Box

    Hey guys! I find it confusing to prove "mv^2/L", the average force acted by the air molecules on a wall in a box. My textbook tells me an assumption "the time during each molecules colliding with the wall of the container is negligible compared with the time elapsed between successive collision"...
  48. B

    Massless beam held against a wall

    Homework Statement Just took my finals and there was one problem that bugged me, I have done these types of problems multiple times and understand it well but this particular problem seems like there isn't enough information. There is a massless beam being held against a wall by a massless...
  49. O

    Conductive heat transfer through basement wall

    Homework Statement In an electrically heated home, the temperature of the ground in contact with a concrete basement wall is 13.8oC. The temperature at the inside surface of the wall is 20.8oC. The wall is 0.118m thick and has an area of 9.43m2. Assume one kilowatt*hour of electrical energy...
  50. P

    Friction Velocity from Law of the Wall

    Hi all, Am currently studying a set of data from a Hot Wire Anemeotry lab that was done a few days ago. The experiment was investigating a turbulent flow of air in a wind tunnel near a flat wall. As part of the write up, we're ment to find the friction velocity from the laminar near wall...
Back
Top