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. L

    Calculating Resistances of a Cavity Wall

    Hi, I am trying to work out the resistances for the following cavity wall. I am having to work backwards. I have the U value, which is 0.48. The brickwork is 103mm, the insulation in cavity is 50mm, lightweight concrete block is 100mm and plaster board is 13mm. I know total thickness...
  2. D

    Nonconductive wall with charge density and finding electric field

    Homework Statement A nonconducting wall carries a uniform charge density of 13.62 μC/cm2. What is the electric field 5.7 cm in front of the wall? Answer in units of N/C. Homework Equations Gauss's law...? The Attempt at a Solution Honestly, this bugger's got me scratching my...
  3. GRB 080319B

    Domain Wall Catastrophe: Is There Any Evidence?

    http://www.starstreamresearch.com/vacuum_reaction.htm" I know this sounds like a lot of crackpottery, especially near the end of the article, but is there any scientific evidence in support of something like this happening?
  4. P

    Why - momentum must be in the wall?

    I was watching MIT Classical Mechanics Lecture16. On completely elastic collision, (at around 24min), professor Walter Lewin shown that when a tennis ball with mass m and speed v hitting the wall, it bouced back with speed v. (Cut from the lecture) << ...Kinetic energy is conserved. All the...
  5. W

    Torque of a woman leaning against a wall

    A woman who weighs 496 N is leaning against a smooth vertical wall. Find Fx= 0= -F Wall = Gx Fy= 0= Gy- Fgwoman (a) the force FN (directed perpendicular to the wall) exerted on her shoulder by the wall T= 0= -Fgw*sin30* ((1.1+.4)/2)- Fgw sin 30 (1.1) + F wall cos 30 (1.5)...
  6. S

    Pressure on a wall due to n N2 molecules (close to ans)

    Homework Statement 4.60×1023 nitrogen molecules collide with a 20.0cm^2 wall each second. Assume that the molecules all travel with a speed of 450m/s and strike the wall head on. What is the pressure on the wall in pascals (Pa)? Homework Equations p=(1/3)*(N/V)*(m*v_rms^2) where...
  7. X

    Catwalk attached to a wall by a hinged held up by a cord

    Homework Statement A folding catwalk of uniform density and length 3r is attached to a wall by a hinge. At the other end it is supported by a cable which makes an angle of θ above the horizontal. If a person of mass m stands a distance r from the wall what is the tension, T, in the support...
  8. H

    Block pushed up against a wall

    Homework Statement A horizontal force of 12 N pushes a 0.5-kg block against a vertical wall. The block is initially at rest. If us = 0.6 and uk = 0.8, which of the following is true? (a) The frictional force is 4.9N (b) The frictional force is 7.2N (c) The normal force is 4.9 (d) The block...
  9. J

    Wind exerting pressure on wall

    The wind in a severe storm is blowing 30 ms perpendicularly to the wall of a large barn of area 80 m2. Calculate the pressure exerted on it, assuming that the air density is 1.3 kg m3. I am quite new to this unit so i really have no idea what to do. Any help apreciated!
  10. R

    What is the impulse given the wall?

    Homework Statement A tennis ball of with a mass of .045 kg and speed of 25 m/sec strikes a wall at an angle of 45 degrees and rebounds with the same spped at 45 degrees. What is the impulse given the wall? Homework Equations I= pf-pi/t The Attempt at a Solution I= mv-mv/t...
  11. C

    Related rates - ladder sliding down a wall physics question

    Hopefully I posted this in the right place. The setup is standard - A ladder 10 ft long rests against a vertical wall. The bottom of the ladder slides away from the wall at a rate of 1 ft/sec. If we let y be the vertical distance and x the horizontal distance, we use the Pythagorean theorem...
  12. C

    What is the average force exerted by the ball on the wall

    A 425 g ball with a speed v of 6.5 m/s strikes a wall at an angle of 30° and then rebounds with the same speed and angle. It is in contact with the wall for 9.0ms. (a) What is the impulse on the ball (take positive as down in the figure)? b. What is the average force exerted by the ball on...
  13. R

    Rate of Change of theta in ladder to wall.

    Homework Statement A ladder 10 ft long rests against a vertical wall. If the bottom of the ladder slides away from the wall at a rate of 1.3 ft/s, how fast is the angle between the ladder and the ground changing when the bottom of the ladder is 6 ft from the wall? Evaluate your answer...
  14. JJBladester

    Dynamic Equilibrium Question (block sliding on wall)

    Homework Statement http://i450.photobucket.com/albums/qq230/JJBladester/06_p51.jpg?t=1223753179 The 2.0kg wood box in the figure slides down a vertical wood wall while you push on it at a 45 degree angle. What magnitude of force should you apply to cause the box to slide down at a constant...
  15. P

    Finding Tension in a String Holding a Meter Stick Against a Wall

    Homework Statement A 0.13 kg meter stick is held perpendicular to a wall by a 2.7 m string going from the wall to the far end of the stick. (a) Find the tension in the string. (b) If a shorter string is used, will its tension be greater than, less than, or the same as that found in part (a)...
  16. F

    Entropy and multiplicity of a gas when adding/removing wall in container

    Consider an isolated system of two ideal, identical gases in thermal equilibrium. Gas A is occupying a volume A, separated by a wall from volume B, where gas B resides. They are in thermal contact. The volumes are the same, so are the pressures and temperatures, and it follows that the number of...
  17. A

    Block held against wall, force problem

    Homework Statement A 12 N horizontal force F pushes a block weighing 5.0 N against a vertical wall. The coefficient of static friction between the wall and the block is 0.60, and the coefficient of kinetic friction is 0.40. Assume that the block is not moving initially. (a) will the block...
  18. D

    Calculating the Force of a Wall on a Wedge

    Homework Statement A wedge with an inclination of angle theta rests next to a wall. A block of mass m is sliding down the plane, as shown. There is no friction between the wedge and the block or between the wedge and the horizontal surface. (Intro 1 figure) what is the magnitude of the force...
  19. L

    Minimum length of the mirror required for a man to see the wall behind him?

    A man of height 2h stands in the middle of a room of length 6h. The height of a wall is 4h. What is the minimum length of a mirror to be placed on the wall in front of the man so that he can see the entire wall behind him?
  20. A

    Kinematics. cannonball was dropped- how far from the wall does it hit ground?

    Homework Statement King Arthur's knights fire a cannon from the top of the castle wall. The cannonball is fired at a speed of 45m/s and an angle of 32degrees . A cannonball that was accidentally dropped hits the moat below in 1.4s . a) How far from the castle wall does the cannonball hit...
  21. P

    Push a Block against a Wall- Static Friction

    Homework Statement A 9 N horizontal force F pushes a block weighing 13.0 N against a vertical wall (Fig. 6-21). The coefficient of static friction between the wall and the block is 0.62, and the coefficient of kinetic friction is 0.42. Assume that the block is not moving initially...
  22. E

    Nuclear Power Liabilities Dwarf Bush's Wall Street Bailout

    "September 23, 2008 Price-Anderson's Blank Check Nuclear Power Liabilities Dwarf Bush's Wall Street Bailout By HARVEY WASSERMAN http://www.counterpunch.com/wasserman09232008.html Is the author correct that US taxpayers are shoulding the cost of insuring the nuclear power utilities...
  23. Cincinnatus

    Schools Graduate school admissions and wall street layoffs

    I'm glad that I'm already in graduate school. Thousands of wall street employees are going to be laid off this year as all these companies go under. I bet most of them will be fairly recent college graduates from prestigious undergraduate institutions. Probably, many of them are going to be...
  24. G

    Motion Problem: Struggling with Angle w.r.t Wall

    Motion Problem! Homework Statement The Attempt at a Solution Okay, so I got number one (6.36904) but I'm having real trouble getting the angle w.r.t the wall. At first I thought of taking the t (from )[/URL] then multiplying it by the acceleration to get the y component of the...
  25. H

    Analysis of Wall Crane: Force & Moment at Pins A & D

    Homework Statement The wall crane in Fig. 3 supports a load of 800 N. Determine the horizontal and vertical components of reaction at the pins A and D. Also, what is the force in the cable at the winch W? http://img182.imageshack.us/img182/992/tutorialse0.jpg...
  26. R

    Devastating Loss: Wall Arch Collapses at Arches National Park

    http://extras.mnginteractive.com/live/media/site297/2008/0808/20080808_051413_wall_arch_before-after-1_300.jpg http://www.sltrib.com/news/ci_10142089?source=rss "Wall Arch, one of the most accessible major arches in the Devils Garden area of Arches National Park, collapsed sometime Monday...
  27. M

    Horizontal Distance from Wall to Mirror Reflection: x

    [b]1. a person whose eyes are H=1.82m above the floor stands L=2..11m in front of a vertical plane mirror whose bottom edge is h= 49.5 cm above the floor, as seen in the figure below. what is the horizontal destance x to the base of the wall supporting the mirror of the nearest point on the...
  28. S

    What is the Average Force Exerted by a Wall on a Bouncing Ball?

    Homework Statement A 3.00 Kg steel ball strikes a wall with a speed 10 m/s at an angle of 60 degrees with the surface. It bounces off with the same speed and angle. If the ball is in contact with the wall for 0.20 s, what is the average force exerted by the wall on the ball? Homework...
  29. I

    Solving Wave Equations with a Wall - Reflection and Amplitude

    Homework Statement We have waves propagating in the air. First part asks for a traveling wave solution in the x direction , given a wave length 2pi and amplitude 3m. I have obtained u(x,t) = 3 cos ( x - 345t). The question then asks what happens if a wall is placed at x=0, what is the form of...
  30. A

    Elastic collision against a moving wall

    Hello, A very basic question, with a bit of confusion. a ball hitting a wall which is not moving with velocity v in an elastic collision has its momentum conserved, opposite velocity; -v. if the ball is to collide with a wall which has a velocity -v, equal speed towards the ball, what is...
  31. A

    Pool Ball Collision: Solving for Angular Momentum and Friction

    Hello, I have a question. I have a pool ball mass M and radius R, that hits the pool table wall, at speed V0, angular speed W0 at an angle alfa0, and then goes away with an angle alfa1, speed V1 and angular speed W1. If the ball wasn't spinning then I think it would be easy to solve with...
  32. J

    Electromagnet that plug into wall outlet?

    electromagnet that plug into wall outlet? I am working on a project for science and and trying to make an electromagnet that will plug in a normal wall outlet (120v ac). I have been searching the internet for a way to do this and have found out very little. I am on a lower budget and want to...
  33. A

    What Causes the Discrepancy in Calculating Wall Shear Stress in Pipe Flow?

    fully developed flow liquid of dynamic viscosity 2.9x10^-3 Pa.s and relative density 0.9 in horizontal pipe of diameter 12mm, length of pipe=200mm and mean velocity is 0.5m/s To find the wall shear stress, i used τ=μ.du/dy = (2.9x10^-3)(0.5/0.012) = 0.121Pa The answer is 0.968Pa, where am...
  34. E

    Rubber balloon is rubbed against a wall and then sticks to the wall

    Homework Statement A rubber balloon is rubbed against a wall and then sticks to the wall. This is because 2. multiple choice a. the balloon and the wall exchange charges through contact b. electrons hop back and forth between the balloon and the wall c. the balloon induces an...
  35. J

    Ladder and wall Statics problem

    cant find an equation for this one.. there is no theta soo i don't know what to do A uniform ladder whose length is 5.8 m and whose weight is 380 N leans against a frictionless vertical wall. The coefficient of static friction between the level ground and the foot of the ladder is 0.54. What...
  36. B

    Circular Motion - Wall of death Problem

    Homework Statement Total mass = 260 kg Coefficient of Friction = 1.00 r = 4 m gmax = 4 g a) Find the minimum speed to keep the rider on the wall of death. b) Find the maximum speed inside the wall of death of the motorcycle based on gmax Homework Equations \mu x...
  37. J

    What must be true to prevent a ladder from slipping against a wall?

    1. A ladder leans up against a wall. If the ladder is not to slip, which one of the following must be true? a.friction between the ladder and wall must not be zero b.friction between the ladder and floor must not be zero c. both a and b d. either a orb e. neither a or b 2. net force...
  38. A

    What is the impulse on the ball from the wall?

    Homework Statement a 250 g ball with a speed v of 6.6 m/s strikes a wall at an angle θ (the angle between the wall and the path of motion) of 30° and then rebounds with the same speed and angle. It is in contact with the wall for 6 ms. What is the impulse on the ball from the wall...
  39. L

    Need calculations for wall climbing RC car

    I am trying to imitate the Airhog zero gravity climber one of these http://www.gmhummer.com/forums/showthread.php?t=111 can someone please help me regarding derieving equations for the suction pressure required and regarding selection of motors for driving suction fans. the toy...
  40. N

    Center of mass of concrete wall

    Homework Statement A cylin drical con crete sil o is 4m in diameter and 30m high. it consists of a 6000kg concreet base and a 38000kg concrete cylindrical concreete walls. locate the center of mass of the silo (A) when it's empty and (B) when it is two thrids full of silage whose density is...
  41. J

    Why a balloon sticks to the wall

    I cannot find this in my book and i cannot wrap my brain around it...i am more of an analytical person... The question is-A negatively charged balloon is sticking to the wall. Does this mean that the wall is positively charged?Explain.Eventually, the balloon falls down. Explain why. The...
  42. J

    How Much Force is Needed to Move a Block on a Wall?

    The weight of the block in the drawing (SEE ATTACHMENT) is 64.4 N. The coefficient of static friction between the block and the vertical wall is 0.580. (a) What minimum force is required to prevent the block from sliding down the wall? (Hint: The static frictional force exerted on the block...
  43. B

    Wall of Death in amusement park - Find number of revolutions

    Here is the question: The Wall of Death in an amusement park is comprised of a vertical cylinder that can spin around the vertical axis. The radius of the cylinder is 3.5 m and the coefficient of static friction between the rider and the wall is 0.32. Find the minimum number of revolutions per...
  44. N

    Constructing a Wall Imaging Device

    I was wondering if it was possible to construct a certain device. There would be a speaker on one side of a wall generating a certain frequency, and on the other side a receiver that would give an image of what was in the wall, such as cabling, studs, etc. I'm sure the technology exists, but I...
  45. M

    Calculating Force Needed to Move 4.8 kg Block Against Wall

    a block of mass 4.8 kg is pushed up against a wall by a force F that makes 37 angle with the horizontal. the coefficients of static and kinetic friction are 0.2 and 0.1 respectively. the magnitude of the force F in N that makes the block just about to slip down: wut i did is: F sin...
  46. B

    Equilibrium Ball attached to wall problem

    Homework Statement A uniform sphere of mass m and radius r is held in place by a massless rope attached to a frictionless wall a distance L above the center of the sphere. Find (a) the tension in the rope and (b) the force on the sphere from the wall. Homework Equations net torque = 0...
  47. D

    How Do I Identify the Nuclei Wall and Two Major Types of Fungi?

    please help me... I can't find the "NUCLEI WALL" it says I must decribe the structure from the fungi and Include the nuclei wall but I can not find it anywhere as well not on the INternet or on books... Maybe someone could helpp me... And the other question is I must Include the...
  48. D

    Simple Ladder leading against a vertical wall become complicated.

    Homework Statement A uniform ladder of length L and weight w is leaning against a vertical wall. The coefficient of static friction between the ladder and the floor is the same as that between the ladder and the wall. If this coefficient of static friction is μs = 0.500, determine the smallest...
  49. R

    Ladder leaning against a vertical wall.

    I have encountered some problems with this exercise: A ladder is leaning against a wall, it will slide due to its weight down the wall and along the floor. I am supposed to determine the time at which the ladder looses contact with the wall, but how? :S
  50. O

    Equillibrium ladder on a wall problem

    Homework Statement http://img90.imageshack.us/img90/4989/scanuy8.png http://img125.imageshack.us/img125/8163/fbdzh7.png The Attempt at a Solution Been working on this one for at least an hour now =/ n_{1} is the normal force of the wall on the ladder n_{2} is the normal force of...
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