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. R

    The angle @ which the particle hits the wall

    dear all, i am working on a problem, but not having found the solution yet. i have a wall section (in a 2D x-y plane) on which spherical balls hit and get reflected. i know the x-velocity and y-velocity of the particle when it hits the wall. i need to calculate the impact (incident)...
  2. S

    Average force exerted on ball by wall at angle

    Homework Statement a 8kg steel ball strikes a wall with a speed of 11.7 m/s at an angle of 35.3 degrees with the normal to the wall. it bounces off with the same speed and angle as shown in the picture. http://img405.imageshack.us/img405/7733/asdfkf7.jpg If the ball is in contact with...
  3. D

    Ladder vs Wall Homework - Force Calculation

    Homework Statement A 10m ladder whose weight is 180N is placed against a smooth vertical wall. A person whose weight is 652N stands on the ladder a distance of 3.2m up the ladder. The foot of the ladder rests on the floor 5.7m from the wall. What is the force exerted by the wall? What is the...
  4. ~christina~

    Ball hits wall and bounces off

    1. Homework Statement A machine designed for quality testing in a handball factory propels the 0.15kg balls toward a wall with a velocity of 9.5m/s at an angle of 60 deg frome the normal to the wall. A typical ball rebounds at 70 deg from the normal at a speed of 9.0m/s. The impact point of...
  5. G

    Static equilibrium with a suspended sphere on a wall

    Homework Statement Homework Equations \SigmaFi = 0 \Sigma\tau = 0 Nw = force of the wall Ff = Frictional force \mu = frictional coefficient T = Tension The Attempt at a Solution \SigmaFx = Nw - Tsin(30) = 0 \SigmaFy = -mg + Tcos(30) + Ff = 0 \Sigma\tau = (R/2)mg -...
  6. K

    Force that the wall exerts on the wedge

    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. Find the magnitude, F_ww, of the force that the wall exerts on the...
  7. S

    How Do You Calculate Angular Acceleration of a Cylinder?

    Homework Statement M, a solid cylinder (M=1.67 kg, R=0.137 m) pivots on a thin, fixed, frictionless bearing. A string wrapped around the cylinder pulls downward with a force F which equals the weight of a 0.670 kg mass, i.e., F = 6.573 N. Calculate the angular acceleration of the cylinder...
  8. J

    Block on an incline adjacent to a wall

    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. http://session.masteringphysics.com/problemAsset/1010942/31/MFS_cf_11.jpg...
  9. V

    How High Does the Rocket Clear the Wall?

    Homework Statement A rocket is fired at a speed of 75.0 m/s from ground level at an angle of 60.0º above the horizontal. The rocket is fired toward an 11.0m high wall, which is located 27.0m away. By how much does the rocket clear the wall? Homework Equations y=vot-1/2gt^2 possibly...
  10. T

    Ball being thrown against a wall

    Homework Statement a 120kg ball moving at 18m/s strikes a wall perpendicularly and rebounds straight back at 12m/s. after the initial contact, the centre of the ball moves 0.27cm closer to the wall. Assuming uniform deceleration, show that the time of the contact is 0.00075s. How large an...
  11. K

    Question: Impulse and Force on a Vertical Window Struck by a Stream of Water

    Homework Statement Question: A stream of water from a hose is hitting a window. The window is vertical, the stream is horizontal, and the water stops when it hits. About 20cm(cubed), that is 20g, of water with speed 1.5 m/s strikes the window each second. Find a) the impulse on the window in...
  12. H

    Tension and Angles of Frame on Wall

    Homework Statement A frame hung against a wall is suspended by two wires attached to its upper corners. If the two wires make the same angle with the vertical, what must this angle be if the tension in each wire is equal to 0.75 of the weight of the frame? (Neglect any friction between the...
  13. N

    Equilibrium of Frictioned Blocks on Wall: A Puzzling Problem

    Homework Statement Consider a smooth vertical wall against which a block is placed.Another block is also placed in contact with the earlier inner block.An external force F is acting horizontally on the outer block towards the wall.There is friction between the two blocks,but no friction...
  14. C

    Can Rebar and Tiebacks Stabilize a Shifting Retaining Wall?

    I saw a similar thread on this issue - so I'm cross posting this forum with a builders forum as well - as I'm very worried about this, and am seeking input ASAP... I apologize if this is off-topic - but I really need some advice ASAP... Last week I cleared an area out next to a fence that...
  15. P

    What are the two principles that prevent walking through a wall?

    I can think of two principles which explains why I can't lesuirely walk through a concrete wall. The HUP and Pauli's exclusion principle. Which one contributes more?
  16. R

    Off the wall soleniod architecture question

    As I understand it: In a regular cylindercal soleniod the winding starts at one point(top) and winds down to the other side(bottom) of a cylindercal core. Once the wind reaches the bottom, the wire returns back to the top and so forth, until the desired winding is achieved, let's say 10 layers...
  17. R

    Will the block move with a parallel force?

    Homework Statement A block of mass 2 kg is pushed against a rough vertical wall with a force of 40N , co-efficient of static friction being 0.5.Another horizontal force of 15N is applied on the block in the direction parallel to the wall. Homework Equations Will the block move? If yes...
  18. E

    Formula for allowable wall thickness

    I need to determine the minimum wall thickness for 1018 CRS for a knife blade. I know the moment, max deflection, greatest safe load, yield strength, MOE, length, density, current wall thickness, etc. However, I can not find a general formula connecting yield strength to wall thickness...
  19. V

    Projectile Motion Question - Clearing a Wall

    Homework Statement Among many other things, determine if a projectile will clear a wall. I am attempting to make a program to respond with a 'yes' or 'no'. So this is not a specific question, it is more of a general "how is this solved?" question. The known values are initial height...
  20. N

    A rubber ball thrown to a wall

    Can anybody explain how the momentum is conserved in the case of a rubber ball (bounced back),when it was throwned to a wall?
  21. A

    Ladder against wall - what is friction needed to prevent ladder from slipping

    Homework Statement A uniform 15 kg ladder whose length is 5.0 m stands on the floor and leans against a vertical wall, making an angle of 25 degrees with the vertical. Assuming that the friction between the ladder and the wall is negligible, what is the minimum amount of friction between the...
  22. P

    Poster Hanging on Brick Wall: Best Techniques

    so I have a brick wall in my room I want to put a poster on. it's the regular small house brick, a chimney to be exact. I've used sticky tack and tape. both hold for a bit and let go after a couple weeks. what would you use?
  23. K

    Calculating Outward Force of a Tornado on a Wall

    Homework Statement Air within the funnel of a large tornado may have a pressure of only 0.2 atm. Atmospheric pressure is 101300 Pa. What is the approximate outward force F on a 11m X 16 m wall if a tornado suddenly envelopes the house? Answer in units of N. Homework Equations P = F/A...
  24. K

    Electric Flux through a wall

    [b]1. The problem is: A vertical wall (5.9m x2.5m) in a house faces due east. A uniform electric field has a magnitude of 150 N/C. This field is parallel to the ground and points 35degrees north of east. What is the electric flux through the wall? [b]2. Homework Equations : Electric...
  25. H

    Mirror on the Wall: Light Reflection Mystery

    If two planes of mirrors (infinite in all directions) were facing each other with nothing in between what would they reflect? How does light come into play in this? If they were not directly stuck to each other (in which case there would be absolute black, no light I assume) but at a distance...
  26. H

    Mirror on the Wall: Light & Reflections

    If two planes of mirrors (infinite in all directions) were facing each other with nothing in between what would they reflect? How does light come into play in this?
  27. C

    Television Wall Mounting - Torque Considerations

    Hello! I'm considering the purchase of a 100 pound LCD television. I anticipate mounting it with an articulating mounting system. The mounting system will allow the television to extend ~27 inches from the mounting wall (thereby creating a considerable torque load on the wall studs used)...
  28. S

    DC-AC inverters and wall outlets

    I was wondering if anyone could provide me with more information regarding DC-to-AC inverters. Specifically, I'm wondering what stops me from hooking up a power source (i.e. lead acid battery, small solar panel, etc) to an inverter and discharging it into the wall. I know that grid-tie systems...
  29. E

    Calculate Wall Flip Height: Person & Speed

    How would you calculate the height needed to do a flip off the wall as described in http://www.wikihow.com/Run-up-a-Wall-and-Flip given the height of the person and the speed.
  30. D

    Calculating the Speed of a 4m Ladder Sliding Down a Wall

    a ladder 4m long rests against a vertical wall. If the bottom of the ladder slides away from the wall at a speed of 30cm/s. How quickly is the top of the ladder sliding down the wall when the bottom of the ladder is 2m from the wall.
  31. P

    Tossing a projectile over a wall beside a platform

    Given: a platform which is 4m high. On the edge of it is a brick wall with height Y. The launch site is some way behind the wall. The landing site is past the wall and beyond the platform. The launch angle is 40 degrees. Find the range. x=vot cos @ (where @=angle) y=vot sin @ range=(vo^2...
  32. wolram

    Electrostatic Wall: David Swenson's 3M Anomaly

    I came across this by accident. http://amasci.com/weird/unusual/e-wall.html. David Swenson of 3M Corporation describes an anomaly where workers encountered a strange "invisible wall" in the area under a fast-moving sheet of electrically charged polypropelene film in a factory. This...
  33. V

    News Wall Street Crash: Was Milton Friedman Right?

    Milton Friedman said that the depression that started in 1929 resulted from banks losing their nerve and failing to shore up the US economy.Was he right?
  34. G

    Calculating Average Force on a Bouncing Steel Ball

    A 9 kg steel ball strikes a wall with a speed of 10 m/s at an angle of 49.8 degrees with the normal to the wall. It bounces off with the same speed and angle. If the ball is in contact with the wall for .0911 sec, what is the magnitude of the average force exerted on the ball by the wall...
  35. J

    Resonant frequency calculation for lengths of thick wall steel pipe

    Homework Statement resonant freq. in air for arbitrary length steel pipe with radius in the 3-8 cm range and wall thickness in the o.5 to 1 cm range Homework Equations unable to find a relevant equation The Attempt at a Solution
  36. J

    Total Force on 8.00m Wide Aquarium Wall Increase

    A large aquarium of height 5.00m is filled with fresh water to a depth of 2.00m. One wall of the aquarium consists of thick plastic of 8.00m wide. By how much does the total force on that wall increase if the aquarium is next filled to a depth of 4.00m.
  37. daniel_i_l

    Solving the Sliding Rod Equilibrium Problem on a Wall

    Here's a question (not homework) that someone asked me a few days ago: you have a rod with length L and mass M that's leaning against a frictionless wall and makes a 30deg angle with the floor. what does the static friction have to be inorder for the stick to stay inequilibrium? What i did...
  38. G

    How Does a Bullet's Mass Change After Penetrating a Wall?

    A bullet with an initial velocity of v0, temperature t0(melting temperature), goes through a wall, and its velocity reduces to v. You know Lb(latent specific heat). You are asked to derive the ratio between the final mass of the bulet and the initial one.Oh, and you know that the energy lost by...
  39. S

    Friction and torque of ladder resting on wall

    Homework Statement A uniform ladder with mass m2 and length L rests against a smooth wall. A do-it-yourself enthusiast of mass m1 stands on the ladder a distance d from the bottom (measured along the ladder). The ladder makes an angle x with the ground. There is no friction between the wall...
  40. J

    How Does Convection Affect Wall Temperature in a Breezy Environment?

    A light breeze of 10mi/hr blows across a metal building. The buildings wall is 3.7m tall and 6.1m wide. A net energy flux of 347w/m^2 from the sun is absorbed by the wall and then dissipated to the air through convection. Assuming the air is 27c and 1 atm and blows across the wall as a flat...
  41. K

    Print ViewA Ball Hits a Wall Elastically

    A ball of mass m moving with velocity v_i_vec strikes a vertical wall. View Figure The angle between the ball's initial velocity vector and the wall is theta_i as shown on the diagram, which depicts the situation as seen from above. The duration of the collision between the ball and the wall...
  42. L

    Beam hinged to wall with a cable (torque, etc)

    Hi. I've tried to answer this questions four times and so far none of my answers have been correct. Any help is greatly appreciated! A uniform 48 kg (m) beam at an angle of 24 degrees (theta) with respect to the horizontal has length of 38 m (L). It is supported by a pin and horizontal cable...
  43. T

    How fast must you throw a snowball against a wall in order to make it melt?

    Hi, I'm new to this forum and I have a question. In my physics class we are discussing energy and work. We are given this problem: "It is exactly 0*C. How fast must you throw a snowball against a wall in order to make it completely melt? (Assume all the energy is transferred to the...
  44. S

    Average Force on Wall from Ice Cubes' Impact

    Small ice cubes, each of mass 5.30 g, slide down a frictionless ski-jump track in a steady stream, as shown in Figure P6.71. Starting from rest, each cube moves down through a net vertical distance of y = 1.40 m and leaves the bottom end of the track at an angle of 40.0° above the horizontal. At...
  45. M

    Tennis ball hitting a wall and rebounding - contact force

    A 57.0 g tennis ball with an initial speed of 25.2 m/s hits a wall and rebounds with the same speed. The figure below shows the force of the wall on the ball during the collision. What is the value of Fmax, the maximum value of the contact force during the collision, if the force is applied for...
  46. R

    Projectile motion of ball at wall problem

    Okay I know this should be easy but for some reason I just can't get it. "You throw a ball toward a wall with a speed of 25.0 m/s and at an angle of 40.0 degrees above the horizontal. The wall is 22.0 m from the release point of the ball. (a) How far above the release point does the ball...
  47. tandoorichicken

    Average wall stress in an aneurysm

    Hints, please? "An arterial aneurysm is a life threatening condition associated with a balloon like expansion of a local segment of an artery. Using a free body diagram determine the average wall stresses in a closed spherical aneurysm with wall thickness h and inner radius r_i. Ignore blood...
  48. K

    Calculating Average Acceleration During Ball-Wall Collision

    A tennis ball with a speed of 25.1 m/s is moving perpendicualr to a wall. After striking the wall, the ball rebounds in the opposite direction with a speed of 12.8 m/s. Take "twords the wall" to be a positive direction. If the ball is in contact with the wall for 0.0105 s, what is the average...
  49. T

    Replacing a Rod with a Tube: Understanding Wall Thickness and Inner Diameter

    The rod shall be replaced by a tube (wall thickness s = da=12).if da is the outer diameter,then the inner diameter is it di=da-da/12 ??
  50. N

    Why Can't We Get Inside a Wall?

    Get into the wall ! I want to say that we can't go into the wall b'cus we know that we are made up of atoms (mainly electrons, protons and neutrons) and all these are fermions, and so as wall. Since fermions follow Pauli's Exclusion Principle. Suppose, we get inside the wall so the fermions...
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