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)

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  1. K

    How do charges in a wall cancel out incoming electromagnetic waves?

    I think that a wall does not actually stop light, I think the electromagnetic waves exist on the other side of the wall, but the charges in the wall provide their own electromagnetic field, such that charges on the other side of the wall feel both forces at the same time and 'cancel out'. Is...
  2. J

    Moments, calculating force exerted on ladder by wall

    Homework Statement Homework Equations Moment = force * perpendicular distance The Attempt at a Solution My book says the answer is 59N, I don't get why my method failed, I use the exact same thing for problems such as calculating the contact force produced by the ground at the end of a...
  3. Shindo

    Boy Holds 100N Sign Against Wall: How Much Push Force?

    Homework Statement If the coefficient of static friction between the sighn and his hands is 0.6, and the coefficient of static friction between the sign and the wall is also 0.6, with what force must the boy push to keep the sign in place? Homework Equations 0.6(Fn)=100 N Fn=166.7 N The...
  4. A

    Ladder leaning on wall, person on ladder.

    http://ronney.usc.edu/AME101/AME101-F14-PS3.pdf number 1 in the link tyty
  5. gfd43tg

    Heat flow rate with non-constant k through plane wall

    Homework Statement Consider a large plane wall with thickness L whose thermal conductivity varies in a specified temperature range as k(T) = k_{0}(1 + \beta T) where ##k_{0}## and ##\beta## are two specified constants. The wall surface at ##x=0## is maintained at a constant temperature of...
  6. gfd43tg

    Heat conduction through plane wall

    When you have energy going through a plane wall, I know that the heat flow rate should be constant, meaning what comes in should go out. But is this true even if it is transient, and a non-steady state process? I think the energy content of the plane will not change for steady state, but for...
  7. M

    Block held at rest against a vertical wall by a horizontal force

    Homework Statement A 5.00-kg block is held at rest against a vertical wall by a horizontal force of 100 N. (a) What is the frictional force exerted by the wall on the block? (b) What is the minimum horizontal force needed to prevent the block from falling if the static coefficient of friction...
  8. Ascendant78

    Suggestions on securing the bottom of a whiteboard to the wall?

    I just bought a whiteboard for my wall, but I have a minor issue. While the top of it had brackets to secure it to the wall, the bottom of it has nothing to attach to the wall. Anyone have any suggestions on a good way to secure the bottom so it doesn't pop up when I'm writing on it?
  9. P

    Pressing a Block against a Wall

    Homework Statement I have this homework question and was able to set up the free body diagrams for the two blocks but got stuck forming the equations in part a. Please help if you can and give explanations - I want to understand the concept for my test coming up. A block with mass M is pushed...
  10. A

    Steel Box Section strength for climbing wall

    Hi, I'm planning to build a climbing wall outside my house, attached to a concrete wall. The climbing wall would be 3 sheets of 18mm plywood (each about 30kgs) - each 2.5m x 1.22m (8ft x 4ft). With the boards set out 2.5m wide and stacked 3 high to give a max height of 3.66m (12ft). I want the...
  11. Fantini

    MHB Kinematics, time taken to a wall disappear

    I'm posting this because I disagree with the answer. Here's the question. You are in a train that is traveling at $3.0$ m/s along a straight horizontal railroad. Very close and parallel to the railroad there exists a wall with upwards inclination of $12^{\circ}$ with the horizontal. Looking...
  12. T

    Collision with a sword placed in the wall at high speeds

    Suppose that I am wearing some super boots that can allow me to travel anywhere from 0 to about 99% of c.Now I use these boots to travel alongside a wall and this wall at some point has a very sharp sword jutting out of it. It is safe to presume that anyone with the sword in his hand can easily...
  13. B

    Pulling a rope on a wall, finding gamma

    Homework Statement Determine coordinate direction angle γ of the resultant force acting at B. Homework Equations Cos\gamma = F\underline{}z/F The Attempt at a Solution The first part was to find magnitude of F\underline{}b. The next part was finding the other coordinate...
  14. E

    How Does Friction Affect the Reaction Force Between Two Blocks?

    Homework Statement There are two blocks against a wall on a frictionless table. I can't really manage a diagram, so please imagine this. There are two blocks, one of 5 kg and another of 10 kg, against each other. The 10 kg one is touching the wall. The frictional coefficient between the...
  15. M

    Calculating Probabilities of Particle in a L-box After Wall Movement

    Homework Statement A particle is in the ground state of a L-box. At t = 0 the wall at x = L is suddenly moved to 2L. (a) If an energy measurement is made after the wall is moved, what is the probability of measuring the energy to be that of the ground state of the new box? (given solution...
  16. H

    Force exerted by one molecule on container wall

    I came across this problem in University Physics: (a) Oxygen 1O22 has a molar mass of 32.0 g>mol. What is the average translational kinetic energy of an oxygen molecule at a temperature of 300 K? (b) What is the average value of the square of its speed? (c) What is the root-mean-square speed...
  17. F

    Projectile Motion (Ball thrown towards a wall)

    Homework Statement In the figure, you throw a ball toward a wall at speed 34.0 m/s and at angle θ0 = 38.0˚ above the horizontal. The wall is distance d = 20.0 m from the release point of the ball. (a) How far above the release point does the ball hit the wall? What are the (b) horizontal and...
  18. tom.stoer

    Shifting of the wall problem II

    I though there's a simple ansatz for a particle in an infinite square well with a moving wall, i.e. in the interval [0,L(t)]. The eigenfunctions and eigenvalues for \left[-\frac{1}{2m}\frac{\partial^2}{\partial x^2} - E_n\right]\,u_n(x) = 0 are u_n(x) = \sin\left(\frac{2\pi n}{L}x\right)...
  19. kini.Amith

    What is the solution to the shifting of the wall problem in quantum mechanics?

    One of the problems in QM i frequently encounter in all textbooks is the shifting of the wall problem which goes like this. Assume a particle is in the ground state (or any stationary state) of an infinite potential well between 0<x<a. If the wall at a is suddenly shifted to 2a, then what is...
  20. P

    Finding Force Needed to Climb Wall: Friction Coefficient u & Angle @α

    Homework Statement A man standing in the corner of the wall tries to climb up by pushing against both the walls, if the friction coefficient between the wall and his elbow is 'u' , then find the minimum force from which the man must push against in order to climb up the wall, given that he...
  21. davidbenari

    Elastic collision against a wall

    In an elastic collision against a wall, where the angle of incidence is equal to the angle of deflection, why is it assumed that friction effected no impulse, and only the normal force did? I can understand if this was stated in the problem by saying "frictionless surface, or whatever" but this...
  22. S

    Variation in tube wall temperature as steam condenses to form liquid

    I'm having a bit of difficulty conceptually understanding a problem. Hoping someone here can clear it up for me. In a simple circular condenser tube (which is cooled by water or air) what happens the tube wall temperature as the steam inside is condensed? Intuitively I would have thought that...
  23. J

    Wall Cavity Insulation Question?

    Homework Statement Hi guys, I have read this question over and over and have no idea where to start, would anyone be able to help. The Question Up to 20% of all heat lost in domestic dwellings occurs through walls. Many modern Australian homes are built by constructing walls...
  24. D

    Conductor wall with internal/external insulation

    Homework Statement Doing my homework I came across the question: why it would be better to have styrofoam on the inside of the house And why it could be better to have it on the outsideThe answer is The steady state will be the same for both but inside: warm and cold quickly Outside...
  25. U

    Heat transfer through an insulated steel wall due to hydrocarbon fire

    Afternoon all, I am interested to hear any and all suggestions as to how one would go about modelling the rise in temperature on the "safe" side of a wall, after a given time period over which the other side was exposed to a hydrocarbon pool fire. The configuration I have been looking at...
  26. P

    Throwing a ball against a wall for projectile motion

    Homework Statement A woman throws a ball at a vertical wall d = 3.4 m away. The ball is h = 1.7 m above ground when it leaves the woman's hand with an initial velocity of 11 m/s at 45°. When the ball hits the wall, the horizontal component of its velocity is reversed; the vertical component...
  27. K

    Uniform rod resting against rough vertical wall supported by a string.

    Homework Statement Uniform rod AB with end B resting against rough vertical wall. Coefficient of friction between wall and rod is μ. Rod is 2m long and has mass 3kg. Rod is kept in limiting equilibrium by a light inextensible string, one end of which is attached to the end A of the rod and...
  28. C

    Basic kinematics - fox jumping over a wall problem

    basic kinematics -- fox jumping over a wall problem Homework Statement A fox is 3.2 m from a 0.5 m tall wall. If it leaps from the ground towards the wall with an initial velocity of 12.0 m/s at angle of 18.9° above the horizontal, how high off the ground will the fox be when it reaches the...
  29. L

    Baseball thrown against a wall

    How do I determine the force per square inch that a baseball would hit a wall? Assume the baseball was thrown at 50 mph? What would be the force? and does that translate into a weight or pressure? Obviously the ball would stop immediately. If we assumed it stopped like a baseball bat of...
  30. gfd43tg

    Navier Stokes thin film on infinite wall

    Homework Statement Consider steady, incompressible, parallel, laminar flow of a film of oil falling down an infinite vertical wall (Figure P-1). The oil film thickness is “h” and gravity acts in the negative Z-direction (downward on the figure). There is no applied pressure driving the flow –...
  31. S

    Forces - A block slides upward on a rough, vertical wall

    forces -- A block slides upward on a rough, vertical wall Homework Statement A block slides upward on a rough, vertical wall at constant velocity when a force F of 60 N acts on it at an angle Ɵ = 60ᵒ to the horizontal. The mass of the block is 3.0 kg. See picture below. a) Using...
  32. O

    Simple 2D random diffusion question (collisions with wall)

    I am looking at an object that diffuses randomly inside a circular plane. What is the easiest way to find the expectation value for how long would it take on average to reach the wall if it was initially placed at a random position? If it is easier: what if the initial position were the...
  33. C

    How much does a bullet penetrate a wall?

    Homework Statement A bullet weighing m = 50g with a initial speed of v = 300m/s hits a wall. The wall is build in a way that the value of the force it causes on the bullet is given by: . The time starts after the bullet hits the wall and F0 = 70N. How much does the bullet penetrate the wall...
  34. S

    Laser in front of a wall - mathemathical physics

    Homework Statement In front of a long, straight, white wall a laser is hanged. Laser is parallel to the wall when we decide to rotate it with constant angular velocity for ##\pi ## so that the laser spot travels over the entire wall. The duration of the turn lasts just as long as it takes for...
  35. M

    Ball attached to string attached to wall, find force against wall

    Homework Statement A solid uniform 50kg ball of diameter 30cm is supported against a vertical frictionless wall using a thin 35cm wire of negligible mass (the wire is attached to the wall, the ball is attached to the wire and rests against the wall). Make a free body diagram for the ball and...
  36. U

    Delta wall and infinite square well potentials ,and 2 other questions

    Consider the following potential function: V=αδ(x) for x=0 and V=∞ for x>a and x<-a , solve the shroedinger equation for the odd and even solutions. solving the shroedinger equation I get ψ(x)=Asin(kx) +Bcos(kx) for -a<x<0 and ψ(x)=Asin(kx) +Bcos(kx) for 0<x<a is it...
  37. Saitama

    Friction and Energy Conservation in Ball Colliding with Wall

    Homework Statement Homework Equations The Attempt at a Solution I have dealt with the case when the wall is frictionless and the rolling ball collide with it but I am not sure how to proceed here. When the ball comes in contact with the wall, the friction due to wall acts in the vertically...
  38. B

    Heat transfer: Plane wall criterium

    Hello fellow scientists, I'm working on describing the heat that's being stored in a sanitation pipe when hot water starts flowing through the pipe. I'm starting off with a simplified approach by assuming that the water in the pipe suddenly changes from 20°C to 60°C. I found a good start by...
  39. A

    Entropy Change of Ideal Gas Upon Inserting Wall

    To preface my question, I know it is related to the Gibbs paradox, but I've read the wikipedia page on it and am still confused about how to resolve the question in the particular form I state below. Suppose a completely isolated ideal gas consisting of identical particles is confined to a...
  40. B

    Find angle with pith ball and vertical wall

    1. The Question: A 10.0 g pith ball, carrying a charge of 1.52 μC hangs from a thread attached to a charged vertical wall carrying a surface charge density σ = 3.57 μC/m2. Find the angle that the thread makes with the vertical. Homework Equations [b]3. My attempt: Tcosθ=mg...
  41. Jilang

    Strange occurrence on office wall.

    Quite late this afternoon I noticed a series of perfectly formed circles of light on the wall above my computer. Where are they coming from I wondered? Putting my hand in front and tracing one back the window, then climbing onto a chair it was clear they originated from the little holes at the...
  42. I

    Solving Equilibrium: 80N Ladder on Wall & Ground

    Homework Statement A)A ladder of weight 80N rests against a smooth wall at an angle of 29 degrees to the vertical with its end on a rough horizontal floor.If the ladder is in equillibrium calculate the reaction (magnitude and direction) of the ground and the wall. Bi)a man of weight 80N...
  43. T

    What Fraction of Initial Height Causes a Plank to Lose Wall Contact?

    Homework Statement A plank of length 2L leans against a wall.It starts to slip downward without friction.At what fraction of the initial height does the top of the plank lose contact with the wall . Homework Equations The Attempt at a Solution Let the normal force from the...
  44. M

    Impulse and Average Force. Ball by the Wall.

    Homework Statement A ball of mass m= .25kg is moving with an initial velocity of \vec{v}=(8.0\hat{x}+8.0\hat{y})(m/s). It rebounds from a wall and has a final velocity (after impact) of \vec{v}= (-5.0\hat{x}+6.0\hat{y})(m/s) a.) Determine the impulse exerted on the ball by the wall...
  45. B

    Pressure vessels, wall thickness

    20 m3 of gas at a pressure of 25 bar is to be stored in a cylindrical pressure vessel 2 m long. Given the following information : The yield strength of the vessel material is 14,000 psi If a factor of safety of 5 is to be used, determine: (a) Whether the vessel should be treated as a...
  46. C

    Is the Stick Lying Against the Wall at Rest?

    Homework Statement A stick is lying at rest against the wall. Which of the following statements is true? A) Friction must be present on both the wall and the floor surfaces. B) The wall surface must be rough, but the floor may be smooth. C) The floor surface must be rough, but the wall may be...
  47. Sir Physics

    Wall Adapter Question: How is 1A Output Possible?

    Hey guys and gals - I was constructing a circuit yesterday and a question developed in my mind. Power out of an outlet is about 120 VAC at like 20 amps as most all of you probably know. So if current MUST increase when voltage decreases how are there wall adapters that only put out 1 amp when it...
  48. P

    Ball hitting a wall at an angle - x and y motion

    Hello! Hopefully this will be a fairly straightforward conceptual problem. A heads up - while this problem clearly deals with momentum and elastic collisions, we haven't actually covered these concepts in class yet. I'm getting the idea, but am still a bit hazy here and there. Homework...
  49. L

    Heat Transfer (Vetical Plane wall)

    Hi Guys, can I get some advice on how do I get started on the question? I'm guessing that natural convection is the key to solving the question. but i have no idea on how to solve it.
  50. S

    Solving Wood Block Force Problem vs Wall: Net Force Calculation

    A 1.0 kg wood block is pressed against a vertical wood wall by a 12 N force (into the wall, at a 30 degrees angle up from the horizontal). if the block is initially at rest, will it move upward, move downward, or stay at rest? I'm working on the problem above, and through Google found this...
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