Wall Definition and 735 Threads

My son occasionally pulls plugs from powerpoints. We tried to get a powerpoint cover but the strong tape here in Japan is weak and it fell off easily. I was just wondering how much electric shock he might get from pulling out the cord when the device (a fan) is operating. Its a two prong...

Homework Statement in the formula of shear stress τ = (V)(Q) / It , Q=Ay = first moment of inertia of area, the area can be located above(or bottom) at the point of interest) when the chosen point is at the wall(boundary) , why shear stress = 0? Homework EquationsThe Attempt at a Solution When...

Homework Statement in the area-moment diagram , why the moment restricted at the wall is 0.594)(1200)(8/3 )? Homework EquationsThe Attempt at a Solution I think \the 8/3 should be 1+3(2/3) , am i right ? Since we know that , the centorid of triangle is 2/3 from the right end , and the...

What is the right method to calculate force the that is applied (by human) on the stationy wall?

Hi all, I need some help regarding domain wall geometries, essentially a bubble of some spacetime (say deSiiter or flat) inside another kind, say anti-deSitter. For simplicity it is spherical symmetric situation and we are intent on using Schwarzschild like static coordinates. So now I am used...

Homework Statement Consider an inertial frame S with coordinates ##x^μ = (t, x, y ,z)##, and a frame S' with coordinates ##x^{μ'}## related to S by a boost with velocity parameter v along the y-axis. Imagine we have a wall at rest in S', lying along the line x' = -y'. From the point of view of...

Hello! I am designing a vacuum chamber made of a vertical glass cylinder free of contact from any other structure, except by the top and bottom where aluminum disks seal the device. Temperature is the same inside and outside. I found on several books the following formula for the hoop stress...

Hey, I would like to showcase my experiment I'm doing. I'm 16, in high school, and the only science I know is chemistry. But that was a default class. I'm learning about Quantum Physics on my free time. and would very much like to become a scientist in that field. To start off this is kind of a...

Homework Statement Homework Equations The Attempt at a Solution [/B]

Consider a ladder slanted like \ of length ##l## slipping against a smooth wall and on a smooth floor. I come to the contradiction that there must be a deceleration in the x direction but there is no force opposing the velocity of the ladder. Its free-body diagram contains a rightward normal...

Hello, all. I've just been working on Kleppner to touch up on my knowledge of mechanics and general problem solving skills and I'm running into a bit of trouble on this leaning pole one in chapter 2. 1. Homework Statement A pole of negligible mass leans against a wall, at angle θ with the...

Homework Statement A horizontal force F is applied to hold a block, mass m = 1.7 kg against a vertical wall. The coefficients of kinetic and static friction between the block and wall are 0.81 and 0.87 respectively. F is gradually reduced until the block falls. Just before it falls, what is the...

My name is Joe. I am 49 and have retired in the last year. I was not planning on this, and have had a hard time getting traction around the house. There are projects that I have had in mind and have dreamed about for years and now, I am finally able to get to them. The hobbies I once did that...

I have derived a few equations to determine temp distribution through pipe wall in subsea conditions. However I am finding it difficult to determine what the wall temperature will be. I need to know and use this temperature to further my analysis. As of now I know the following parameters...

How can I calculate the pressure exerted by a fluid on the walls of the vessel that is being agitated. The vessel is not pressurised. I have to calculate the resultant pressure on the walls to calculate the thickness of the vessel walls.

I read somewhere that antibiotics can have no effect on Mycoplasma as they do not possesses a cell wall.But How ? Antibiotics should be able to get into the bacteria very easily when there is no cell wall,right ?

Hello All, I am a semi trailer manufacturer who just started building specialty trailers for various industries. Recently I have been asked to develop a trailer to carry peanuts from the farms and deliver them to ware house. To design the trailer light enough, i have decided to go with...

Homework Statement H3-1 Determine the maximum height on the wall to which the firefighter can project water from the hose if the speed of the water at the nozzle is 20 m/s. The firefighter stands 18 m away from the wall and holds the nozzle 1.2 m above the ground. Homework Equations The...

Hi - Can anyone help me out with a question. The answer seems obvious, but maybe so obvious that I'm jumping to wrong conclusions! Just been reading Guy Martin's book "When your dead, your dead" (good read by the way) and one of his stories is about breaking the world speed record for a wall of...

Homework Statement A man tiles a wall with 50 square tiles. Each tile has sides of 20 cm. The wall is ten tiles high and 5 tiles long. 2. Homework Equations No real equations to use here... The Attempt at a Solution What length is the wall? 20 cm x 5 = 100 cm= 1 m What height is the wall...

Hello, Me and my buddys doing aproject on Heat transfer. we choose wall heating as our subject and we have some issue on modeling the system. our system is : two walls, one exposed to the atmosphere the other is the house wall. between them there's a pipe with hot water and some aire. we...

I am trying to understand in non-mathematical terms the meaning and physical reality posed by Einstein’s law which tells us that the speed of light is the same relative to all observers. I start with a basic hypothetical: Observer A observes B riding a motorcycle that is traveling at 50 mph...

Is it similar to the Newton's cradle principle? This is fluid mechanics/control volumes. There is fluid flowing through a duct and it's being analysed using a control volume surrounding the duct For example in this question the atmospheric pressure is having an affect on the fluid within the...

What is the "plane of symmetry", "zero velocity wall" and "free surface" terms which I have seen in Polyflow? It says in Vnormal=Fs=0 for plane of symmetry and Vnormal= Vs= 0 for zero velocity Wall. Now I get when Vs=Vn=0 it means that the wall isn't moving and it's in a static state but didnt...

I'm Having a part machined with a cylinder shape approximately 14 inches in length with a cylinder hole in the center with a diameter of .930 . I have no idea how thick the cylinder wall needs to be. I have looked up and used hoop stress calculators online but I do not understand if they take...

So I have learned that an interaction term in a Lagrangian like: L= kρσ can result in "domain wall" problems between the fields ρ and σ. I imagine this means that it can result in particles spontaneously changing mass, spin, or some other property, violating conservation laws. Is that why this...

Hello everyone, I am currently studying traveling waves and reflection but I didn't understand a part of my last lesson. If we consider a string with a loose end and the other end attached to a wall we expect the string to have zero displacement at the wall and to have a reflected wave...

Homework Statement a tennis ball of mass m = 0.075kg is thrown at a wall with a speed of v = 15m/s. It strikes the wall at a 45˚ angle and rebounds with the same speed at 45˚. What is the impulse given by the wall? Homework Equations impulse = Change in mass x Change in velocity The...

1. State the problem A plane wall consisting of three different materials, each of constant thermal conductivity k. Assume steady-state temperature distribution. a) Comment on relative magnitudes of q(dot)''2 and q(dot)''3 and of q(dot)''3 and q(dot)''4. b) Comment on the relative...

Homework Statement I am trying to understand how to obtain the required wind coefficients of 0.60, -0.30 and -0.60 for the problem, by using the given figure Homework EquationsThe Attempt at a Solution for the windward side, does it correspond to theta = 0 since the question says "normal...

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

Hey guys! Supposedly I will need to design a floor with slab, beams and columns. Brickwall should rest on top of beam as possible. How about low wall, does it needs to rest on top of beams as well? Thanks! Harry.

Homework Statement Homework Equations Young's Modulus, E=σ/ξ Stress,σ =F/A Strain, ξ=x/L The Attempt at a Solution As diameter and tension are constant, so stress must be constant I assume.. So for the same Young's modulus, if stress is halved, then strain must be halved too I guess. But I...

Homework Statement A rod extends from a vertical wall at an angle of 27º from the horizontal. A 2.5-kg lamp is mounted at the end of the rod. After John throws his 300-g winter coat over the lamp, what is the magnitude of the tension in the rod? The answers choices are: A) 30N B) 70N C) 27N D)...

The attached image shows the top of a residential air handling unit, and how a flexible silencer (right) and a spiral duct (left) is attached. The duct is steel, and the silencer aluminium. The owner proposes that fan noise will transfer to the room through the centimeter wide piece of exposed...

So, I've already answered parts (b) and (c), but I'm struggling with (d). Thanks in advance for any help! 1. Homework Statement "A woman throws a ball at a vertical wall d = 6.0 m away. The ball is h = 3 m above ground when it leaves the woman's hand with an initial velocity of 16 m/s at 45°...

Homework Statement A uniform ladder which is 10 m long and weights 300 N leans with its upper end against a smooth vertical wall and its lower end on rough horizontal ground. The bottom of the ladder is 6 m from the base of the wall. A man weighting 700 N stands on the ladder at a point 6 m...

If I were to drop a sphere down a tube of fluid. What are the effects of the wall of the tube on the sphere? Assuming the sphere has an extremely low Reynolds number of less than 1. Is it right to say that the ratio of the radius of the tube and the radius of the sphere has an effect on the...

In bacteria there's a capsule but I'm not sure what it is/does.

In the figure we see two blocks connected by a string and tied to a wall, with θ = 33°. The mass of the lower block is m = 0.9 kg; the mass of the upper block is 4.0 kg. Find the tension in the string that is tied to the wall. -I have the forces of Block A as Tension, Normal Force, and Gravity...

Are there any good design resources on masonary wall design? Specifically, I was considering an above-ground, open-to-sky, rectangular tank storing approx. 25 m3 of water in it. Is it possible / economical to build such a tank out of masonary alone or does an RCC construction become economical...

Homework Statement A uniform ladder rests against a vertical wall where there is negligible friction. The bottom of the ladder rests on rough ground where there is friction. The top of the ladder is at a height h above the ground and the foot of the ladder is at a distance 2a from the wall...

I am making a game where a ball rolls along the ground collecting coins. The ball is inside four walls. I want to know what the equation for the ball hitting the wall and coming back is. I want the speed and to find the angle aswell. The ball stays at a solid speed of 10 and has a mass of 1 kg...

hi, i was wondering if a thin walled cylinder was storing water, where the pressure is dependent on the depth of water, how would you calculate the stress in the wall at some depth, eg are you allowed to use the thin walled pressure vessel stress formula: stress = pd/2t and use the water...

Please see the attached image. I understand the area represents the resultant force per unit width. But I'm unsure what equation to come up with for the purple area. I'd appreciate a little patience here, it's been ages since I did this. Thanks

Homework Statement A ball of mass m rotates without sliding at velocity v1 and hits a wall. it rotates backwards at velocity v2. what is the energy loss. Homework Equations Kinetic energy of a rigid body: ##E=\frac{1}{2}I\omega^2## Moment of inertia of a ball round it's center...

Homework Statement A rope is attached to a wall on one end and to a car on the other end. Someone pushes up on the rope and the car starts to move when the rope makes an angle of 5o with the floor. Mcar=2500kg Homework Equations ΣFx=ma ΣFy=maThe Attempt at a Solution Look at the car and the...

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...

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

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?