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. Dong Aleta

    Friction Factor for Wetted Wall Columns

    Hi! I encountered this problem that asked for the friction factor of a very dilute SO2-air gas mixture in a wetted wall column. All the necessary information were given to compute for the Reynold's number. What I want to know is does having a wetted wall make it a different case (ergo use...
  2. ZapperZ

    Insights You Will Not Tunnel Through a Wall - Comments

    ZapperZ submitted a new PF Insights post You Will Not Tunnel Through a Wall Continue reading the Original PF Insights Post.
  3. V

    Why a small wall falls apart on being hit by a bullet?

    When a bullet from a rifle hits a small wall, the wall falls apart. According to Newton's third law of motion, the wall should also exert an equal and opposite force as exerted by the bullet. The wall should be able to withstand the force exerted by the bullet on it. Why doesn't this happen?
  4. andyrk

    Understanding the Relationship Between a Compressed Spring and Attached Wall

    When we compress a spring attached to a wall, the wall also exerts the same force as we do, otherwise the spring would accelerate (which it doesn't). So does that mean the wall compresses the spring? If not, why? If yes, then why do we have compression of x (done by us) only?
  5. P

    Slab on a Brick wall (Only 3 columns)

    I have a 3 story building. Will it be possible to put a slab (to make it a roof top) on a brick wall at 2nd floor? It was designed to construct a roof. Dimensions of brick wall: 8' X 14' Or please suggest me the best way to make a roof top on it.
  6. R

    How long does the box take to reach the wall?

    Homework Statement A stationary 10 g box is pushed with a force 20 Newtons across a level floor. How long will it take the box to reach a wall 10 meters away? Homework Equations Applied force - Friction Force? The Attempt at a Solution I am unsure how to attempt this. Do I need to know the...
  7. A

    Calculate the force of ball on an incline leaning on a wall

    Hi all, I'm working on a problem from the Feynman exercise book, and have been racking my brains for an answer, so would really appreciate some help here. The problem seems simple enough: A ball with a 3cm radius, weighing 1kg rests on an inclined plane (angle alpha) and also touches a...
  8. L

    Distance to the nearest node along the back wall

    Homework Statement Two 512Hz tuning forks are placed 3.0 m apart on the bench at the front of a classroom. Each is 2.0 m from a side wall and the room is 7.0 m. The speed of sound is 343 m/s. b) If the back wall room is 10.0 m away what is the distance from the back corner of the room to the...
  9. E

    Calculating the speed of hammer to drive a nail in the wall

    1. We know that we need 5000N to drive a nail 2.5 cm into a wall. How fast does a hammer of 500g mass have to be in order to drive the nail in the wall in one stroke?(look at the picture if it is unclear. The 2 cm in the picture should be 2.5cm) 2. F=m*a W=F*x x=distance 3. I thought it...
  10. Lieberkuhn

    Heat transfer through a multi-layered wall

    Homework Statement A furnace wall is made up of 3 layers: 1. 4mm layer of material with thermal conductivity of 52 W/m.K 2. 2mm layer of material with thermal conductivity of 20 W/m.K 3. 1mm layer of material with thermal conductivity of 3 W/m.K There is an air gap between layers 1&2 with a...
  11. ChipY

    AM Radio signal IS sounding from my wall heater

    I am a video and sound engineer. There is clearly AM radio coming from my wall heater. An earlier thread on this topic discussed the possibilities but ultimately left the subject with an assumed crazy old lady's false perception. I assure you this is happening. There is a 50,000W AM station...
  12. R

    Forces in Equilibrium acting on wall climber

    < Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > Hello and thank you in advance for any help. I am currently studying physics and having difficulty working out a forces at equilibrium problem. With limited given variables, I am unable to see...
  13. R

    Pipe wall thickness, barlow equation problem

    Hi guys I am working on some project that involves pipe wall thickness calculation, and I have one problem. here is the explanation of the example: http://pokit.org/get/?24c6e34b749030e74662402372ce5fc7.jpg Please, can some one tell me what means tf/m2 (ton force/square meter ?) and how to do...
  14. M

    Wall strength and tension on rope-pulley system

    Hello, My friend needs to transfer construction objects across a pond, came up with this idea of tying a rope between the pond and a big tree then transfer objects through a pulley, I'd like to know how to calculate the tension and will the thin concrete wall withstand the load? Here a diagram...
  15. R

    Tangential Acceleration of Object moving in cylindrical wall

    Homework Statement An object slides along the ground at speed v at the base of a circular wall of radius r. The object is in contact with both the wall and the ground, and friction acts at both contacts. The wall is vertical and provides no force in the vertical direction. (i) Show that the...
  16. anandzoom

    Thermo flask - wall - air pressure

    In a thermo flask the air between the outer and under wall is sucked out and a vacuum is created. So the air pressure should push the outer wall towards the inner wall and vice versa. But it doesn't happen. Why?
  17. gracy

    Final velocity in SUVAT equations -- ball thrown from a wall

    Homework Statement :[/B]There is a wall of height 30 meters.From the top edge of the wall a ball is thrown up with a velocity of 5m/s.Find the time taken by the ball to come to the base of the wall. Take g=10 m/s^2 Homework Equations :I used V=u+at[/B]The Attempt at a Solution v=0 as ball will...
  18. Y

    Ladder on rough ground against rough wall

    1. Homework Statement A ladder on the rough floor is leaning against a vertical rough wall. The ladder has length l and mass m. The coefficients of friction are μ for both contact surfaces. What is the smallest angle between the ladder and the floor? Homework Equations ∑F=ma ∑τ = F⊥ r fs ≤ μsN...
  19. D

    Tension on bolts in anchor plate on concrete wall

    Hi. I need help calculated the tension on bolts in an anchor plate. The plate is bolted to a concrete wall with four bolts (see the included image). A bending moment acts on the plate, offset a bit up/down. The bending moment acts from up to down so that the upper two bolts are in tension and...
  20. gracy

    Two blocks pushed against wall

    Homework Statement ;Given in the figure are two blocks A and B of weight 20 N and 100 N, respectively. These are being pressed against a wall by a force F as shown. If the coefficient of friction between the blocks is 0.1 and between block B and the wall is 0.15, the frictional force applied by...
  21. E

    How can I prevent deformation of an ultrathin-walled tube during insertion?

    Designing mechanical system where two concentric tubes will pass through high density membrane. Outer tube will have tapered end .Outer tube will have ultra thin walls (about 0.3-0.5 mm) .Inner tube is more rigid and will fill all space inside outer tube,decreasing chance for deformation of...
  22. B

    Calculating temperature and heat flow in a wall

    Homework Statement Consider the following multi-layer wall consisting of an interior insulation layer and an external light-weight concrete layer. Calculate the heat flow thorugh the structure and the temperature at the interface between the two materials. Layer 1: Thermal insulation...
  23. M

    Overcoming the First-Year Physics Wall: Advice for Struggling Students

    I'm a first year physics major, and I feel like I'm hitting a wall in physics. I have been doing well in physics so far, even though I have been studying more and more and I just feel like I am hitting a wall and not learning anything. Even though I still like physics a lot, I'm losing the...
  24. M

    Find the weight of a sphere connected to a pulley and to wall

    Homework Statement The system of 2 spheres is in equilibrium. Figure: . If the weight of the second sphere P2=20N, ABC=60 degrees and BAC=30 degrees, find the weight of the first P1 and the force that is applied on the drum of the pulley. Homework Equations P1=m*a The Attempt at a Solution...
  25. nate crosby

    Free Body Diagram -- forces on a structure over a balcony wall

    Hi, I am trying to work out the forces involved at the contact points in a design of a structure over a balcony wall. I have drawn up the cross section of the situation equilibrium, with a tolerance. I want to find out what forces will be acting on the structure and the balcony wall when a...
  26. Felipe c.

    Finding Force P for Mass on Wall: Exam Problem Help

    Hello, i was practicing for an exam and i found this problem on my book: A block of mass 3.00 kg is pushed up against a wall by a force P that makes a 50.0° angle with the horizontal as shown in the figure. The coefficient of static friction between the block and the wall is 0.244. a) Determine...
  27. A

    Box sliding down wall at constant speed

    Homework Statement The 2.0 kg wood box in the figure slides down a vertical wood wall while you push on it at a 45 ∘angle. https://session.masteringphysics.com/problemAsset/1070374/4/06.P51.jpg Homework Equations ΣFY = FPY - mg The Attempt at a Solution I know that since there is a constant...
  28. P

    Heat flux through wall question

    Homework Statement I was given this question. The wall of a building is constructed of face brick (10cm thick) and concrete block (50 cm thick) with an air filled cavity (5cm thick). The interior and exterior convection coefficients are 8.3 W.m^-2.K^_1 and 35W.m^-2.K^_1 respectively. The...
  29. A

    Calculation of the force exerted by a liquid

    Question: The height of the given vessel is h,and the width of the given vessel is b (as given in the diagram). The density of the liquid is r.Find the force exerted by the liquid on the slant wall. Relevant formulae : P = F/A F = Vdg An attempt at the solution...
  30. D

    Kinematics Question -- A soccer ball bounces off a wall

    Homework Statement "A person kicks a soccer ball at an angle 30° above the horizontal on the ground. The ball then hits a wall at an angle 15° below the horizontal 4.9 seconds later. Determine the height at which the ball hit the wall." (Assume acceleration due to gravity is 9.80m/s2 [Down].)...
  31. S

    How can I calculate wall thickness for vacuum distillation?

    Hi everybody, I want to design two industrial vacuum distillation systems. The dimension of my distillation tanks are as follow: (1) A Horizontal Cylinder Tank with 200 cm length and 200cm diameter (total volume = 6300 liter) (2) A Horizontal Cylinder Tank with 400 cm length and 290cm diameter...
  32. Nugatory

    Odd multimeter readings with AC->DC wall adapter

    Is there any reason why my basic Radio Shack multimeter might consistently read high when I use it to test the output voltage of an AC->DC wall adapter? I try it on a 4.5V adapter rated for a few hundred mA and it reads close to 10V... I try it on a 6V one and it reads around 12V... but then...
  33. C

    A woman throws a ball at a vertical wall d = 5.0 m away.

    A woman throws a ball at a vertical wall d = 3.2 m away. The ball is h = 1.6 m above ground when it leaves the woman's hand with an initial velocity of 14 m/s at 45°. When the ball hits the wall, the horizontal component of its velocity is reversed; the vertical component remains unchanged...
  34. Z

    What is the average force on the wall?

    Homework Statement A ball hits the wall in a normal direction with v=10m/s. After the hit which lasted 0.2 Seconds, it turned in the same direction with v=10m/S. Knowing that its mass is 0.5 kg, find the average force that hit the wall. Homework Equations F=m*a, a= (v-v0)/t The Attempt at a...
  35. minimario

    How Do Friction Forces Act on a Ladder Leaning Against a Wall?

    Homework Statement When a ladder is learning against a wall with friction both on the wall and against the ground, how do you determine the direction of the 2 friction forces? Homework EquationsThe Attempt at a Solution [/B] I found a pic online, why is this true?
  36. K

    Static friction between a cylinder and a wall

    Homework Statement The cylinder in the drawing weighs 100[N]. there is a horizontal rope at the top that prevents it from rolling. what is the coefficient of friction if it's on the verge of movement Homework Equations Friction force: f=μN The Attempt at a Solution The whole weight of the...
  37. J

    Black/white radiator vs white/black wall: radiation

    Hi, Situation A: Black radiator in a room with white walls. Situation B: White radiator in a room with black walls. Which one is the most efficient situation? I know that convection is dominant if you look at a radiator, but i would like to know the answer in terms of radiation. Thank you :)...
  38. S

    How to describe motion of the wall of a liquid container?

    Hi, I wonder I cannot solve the following simple problem. I really don't know what kind of equations are relevant. Imagine a rectangular tank, with vertical walls containing some water. The surface area is big. The wall of the tank is movable without friction, and its mass is negligible. All...
  39. B

    What Type of Math is Used by Wall St. Financial Wizards?

    What type of math is used by those who work on Wall St. and make the so-called "big bucks?"
  40. J

    Stability: Leaning Horse against a Wall

    Homework Statement Data: ##m = 500\ kg## Distances given in the image. Homework Equations ##\tau = rF\sin(\theta)## ##F_{net} = ma## The Attempt at a Solution It seems this problem is intended to be one where torque applies, but I don't see it in that way. And of course my answer...
  41. A

    Finding the Angle between Thread and Wall for Sphere A

    1. The problem statement, all variables and given/known Sphere A has a mass=4.2X10^-2 kg and iA tethered to a wall by a thin thread. Excess of electrons for A=1.2X10^12 Excess of electrons for B=3.5X10^12 Distance between A and B=0.23m find the angle between the thread and the wall Homework...
  42. P

    Shear stress in thin wall beams

    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...
  43. M

    What is the Equation for Water Pressure on a Dam Wall?

    Homework Statement Consider a simple model of a free-standing dam, depicted in the diagram. Water of density ρ fills a reservoir behind the dam to a height h. Assume the width of the dam (the dimension pointing into the page) is w. (a) Determine an equation for the pressure of the water as...
  44. G

    Ladder leaning on a wall problem -- Please help me

    Homework Statement A ladder 8m long weighing 200N is resting against a rough vertical wall. A man of 720N climbs the ladder at point M. Take the coefficient of friction for both surfaces to be 0.25. The top of the ladder is point A and the bottom is B. The ladder makes an angle of 30 degress...
  45. K

    How to calculate thickness of the wall in a wire chamber

    Homework Statement This is a question on multiple coulomb scattering in a wire chamber momentum p = 500MeV/c wire resolution = 120 microns distance from wall to wire = 0.01m radiation length of wall material X_0 = 2E-3 m mass of charged particle m_{\pi} = 139.6 MeV/c^2 charge z = 1 How thick...
  46. N

    Gravitational potential energy of a retaining wall

    Homework Statement Forty 2.0kg blocks 20.0cm thick are used to make a retaining wall in the backyard. Each row of the wall will contain 10 blocks. You may assume that the first block is placed at the reference level. How much gravitational potential energy is stored in the wall when the blocks...
  47. powerof

    Analyzing Forces and Torque of a Slipping Rod

    Homework Statement [/B] As a diagram any of the countless images on the internet serve well: Suppose the static friction was not sufficient to maintain the rod in a static equilibrium and it starts slipping/sliding. It has an initial angle theta with respect to the ground. Assume there is no...
  48. 2

    Force parallel to a smooth wall?

    Hello! My question is quite a quick one- I was wondering whether it is ever possible to have a smooth wall exerting a force parallel to it (and not just perpendicular to it). For example, if you were to place a see-saw by a smooth wall so that the wall is holding one of the see-saw ends below...
  49. P

    Min Friction Factor to Maintain Angle of Beam on Wall: 60°

    Homework Statement Homogenous beam rests on smooth wall such that it forms an angle of 60 degrees with the ground (picture is rotated). A body of mass m = 60 kg rests 7 m from the end of beam which lies on ground. Mass of beam equals 15kg and length equals 10 m. What is the minimal friction...
  50. 9

    Static Friction -- A ladder leaning against a wall starts to slip

    Homework Statement A ladder,10 m long and having a mass of 25 kg, rests on a rough horizontal floor and is supported by a rough vertical wall. The ladder is inclined at 60 degrees as shown and starts to slip when a person having a mass of 75 kg has climbed halfway up it. The coefficient of...
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