What is Flat: Definition and 495 Discussions

I haven't seen any theory that describe the universe how it becoming flat, from what I saw from here is, universe is isotropic at the beginning, then become flat. What is the explanation here?

A uniform disk is lying on a flat, frictionless surface, and a force is applied as shown: http://www.freeimagehosting.net/uploads/ae622047b5.jpg What will be the motion of the disk.. more importantly, the motion of center of mass of the disk. will it move in a straight line, or will it move...

Homework Statement In mos capacitor, energy band will bend because of different work function between M&S. But Why apply a "flat band voltage" to flat the bent band? what's the purpose? Homework Equations The Attempt at a Solution I have been looking for the answer from...

Homework Statement A flat, uniform, disk, of radius 1.5 m and mass 10 kg, is rolling on its edge with a translational velocity of 12 m/s. What is the kinetic energy of the disk? Homework Equations not sure which one but I'm guessing it's one of these two: K = .5(I)(w)^2 K =...

Why did people think the Earth was flat?

This is driving me nuts. (I originally posted this to the coursework section, but in thinking about this, I felt that it might not be the right place (this is for a term paper, not really any ongoing coursework, so there). Hope I'm not imposing ... I feel quite embarrassed on this one, since it...

I would like some help in calculating the basic Friedman equations starting from the flat FRW universe line element, Once I have calculated the Christoffel symbols for this metric how do i get to the Friedman equation, any link to a good book will be really helpful, thanks, seetesh.

In another thread I was reminded that there is a `clear` distinction between `curved space` and `curved spacetime`. However, to be honest, I wasn’t sure that I really understood this difference and was pretty sure I couldn’t visualise it. So, by way of a learning process, I wanted to see if...

Homework Statement A narrow flat coil wound on a square frame has 160 turns and sides of 34.0 cm. It carries a current of 5.30 A and is positioned in a 0.260- T magnetic field. What is the maximum torque that can be exerted by the field on the coil? Homework Equations Torque = (Number...

In the usual "windowless room" thought experiment it is stated that there is no experiment which can be performed which will determine if the room is undergoing "uniform accleration" far from any massive body or is in a "uniform gravitational field". The two situations are therefore said to be...

Many of the formulas of physics assume a background of flat spacetime. But it's natural to think that this is just a special case of a more general formulation in curved spacetimes. So I'd like to develop a general procedure to transform flat space formulas and integrals, etc, into their curved...

Is there a general procedure to convert or transform a function that is defined on a flat space into an equivalent function in curves spaces?

space is flat what the hell does this mean. It must be at least six foot thick as that's how tall I am? how thick is space it must be pretty freakin thick. Is it flat like a turkish bread (ie sort of flat but thick as well) or flat like a balloon where the skin of the balloon is some...

Two photons are traveling parallel to one another. Can the photons orbit one another perpendicular to the direction of travel? That is can the photons follow a stable long spiral path in flat space-time. The photons have no rest mass but they are not at rest. If they are traveling (...

1. Problem I need to find the principal moments of inertia about the center of mass of a flat rigid 45 degree right triangle with uniform mass density. 2. Useful Formulae I_{xx}=\int_{V} \rho (r^{2}-x^{2}) dV I_{jk}=\int_{V} \rho (r^{2} \delta_{jk} - x_{j} x_{k}) dV 3. Attempt at a...

If we have as a manifold euclidian R^2 but expressed in polar coordinates... Do any circle centered at the origin constitute a geodesic? Because I think it parallel transport its own tangent vector.

hi guys.. i don't know much about physics. and if my questions sound stupid .. please excuse me. According to what I've known, the water surface is flat, and we use it for some sort of measurement like a water level, but if we go to outer space, we would see the water surface not flat , it's...

I am designing a spinal disc with 2 metal endplates. These endplates are rectangular in shape and are fixed to form a flat contact surface with the vertebrae bone surface. My question is based on the bending stress of these metal endplates. I need to work out the possible thickness of these...

I am designing a spinal disc with 2 metal endplates. These endplates are rectangular in shape and are fixed to form a flat contact surface with the vertebrae bone surface. My question is based on the bending stress of these metal endplates. I need to work out the possible thickness of these...

[SOLVED] Newton's Law Flat Curve Homework Statement You are riding in a school bus. As the bus rounds a flat curve at constant speed, a lunch box with a mass of 0.470 kg suspended from the ceiling of the bus by a string of length 1.88 m is found to hang at rest relative to the bus when the...

Is it even possible? Or am I just flat out wrong once again? Whenever I really need to procrastinate, I turn to writing a calculus book. In this case.. For about three days I pursued the problem of whether or not you can teach topology before "rigorous Calculus". Is it even possible, to...

Homework Statement A space-time is said to be conformally flat if there is a frame in which the metric is g_{ab} = \Omega^2 \eta _{ab} \text{ with } \eta_{ab} the metric in Minkowski. Is the general Friedmann-Robertson-Walkers space-time with line element ds^2 = -dt^2 +a^2(t)(dx_1^2 +...

Past and future light cones in flat infinite space have straight sides at 45 degrees and their boundary surface is flat i.e. if you cut the side of the cone (one straight cut) you could spread it on a flat suface. We can tilt the cone by injecting spatial speed. I have no issue with this :cool...

Homework Statement http://mathworld.wolfram.com/images/eps-gif/UniversalCoverDoubleTorus_1000.gif Why do you need both the orange and the purple cuts to lay the double-torus flat? Why can you not connect the orange cut going right and the purple cut going left under the torus. It seems like...

I am trying to repair my 1920s pier and beam house and have a situation where I need to slide under two butted beams on top of a post the thinnest steel I can that will support the two beams. What would help me determine this would be a general idea of how to compare the strength of a flat...

I would appreciate help in objectively disproving the following "alternative physics" proposition: "The large-scale geometry of the universe is compelled to be eternally flat because gravity causes the universe to expand at exactly the escape velocity of its mass/energy contents." This...

[bpump add air into the flat tire in the gas station. The compressed air is at 180 psia and 60F(+460). the tire is initially at vaccum, therefore p0=0 psia. Air is added into the tire until it reaches Pf =32.9 psig which is (23.9+14.7=47.6 psia), then stopped . this process is adiobatic which...

A uniform flat disk of mass M and radius R rotates about a horizontal axis through its center with angular speed ωi. a) What is its angular momentum b) A chip of mass m breaks off the edge of the disk at an instant such that the chip rises vertically above the point at which it broke off. How...

shear stress, what is a flat tie bar...? Homework Statement two lengths of flat tie bar are connected together by a lap riveted joint with three rivets each 10mm in diameter. Calculate the maximum pull that can be applied to the tie-bars if the shear stress in the rivets is not to exceed...

pump add air into the flat tire in the gas station. The compressed air is at 180 psia and 60F(+460). the tire is initially at vaccum, therefore p0=0 psia. Air is added into the tire until it reaches Pf =32.9 psig which is (23.9+14.7=47.6 psia), then stopped . this process is adiobatic which...

I'm working on a computer simulation, but I'm not sure how to approach this problem. I want to find the change in angular velocity on an object rotating on top of a flat plane. So far this is what I have: (* == multiplication not dot product) Ff x r = I * alpha Ff x r = I * dv/dt I...

Ohh is this a joke? http://en.wikipedia.org/wiki/Flat_Earth_Society http://theflatEarth'society.org/forum// They even use physics theories to "prove" that Earth is flat. Comments? -link

I just want to make sure my understanding is correct. In a "flat" universe, the total density of the universe matches the "critical density". As a result, the universe will expand forever, and never "fall back" into itself. The shape of a flat universe, as the name suggests, is flat like a...

Homework Statement While coasting along a street at .5m/s, Mieko, a 15kg girl in a 5kg trolly, sees a vicious dog in front of her. She has with her only a 3kg bag of sugar which she is bringing home from the store, and throws it with forward velocity of 4m/s relative to her original motion...

Sorry for posting this in the wrong spot. Thanks for moving it. If there is a consensus throughout mainstream science that the Universe is flat, I have a few questions that I have not found the answers for.What types of explosions are flat? What forces are required to keep the universe flat...

Homework Statement A block of mass m is pulled along a rough horizontal surface by a constant applied force of magnitude F that acts at an angle theta to the horizontal. The acceleration is a. Express all algebraic answers in terms of m, F, theta, and a. A. Derive an equation for the normal...

Hi everyone, I'm puzzled by this phenomenon - when there's a thin sheet of water flowing in the street, it forms little wavefronts which appear periodic. Obviously the water gets thin enough to interact with the rough asphalt surface, but how does the random texture manifest an organized...

It seems to me that current thinking leans toward an expanding and accelerating universe that is neither positively nor negatively curved, but rather, essentially, 'Flat'. How does this thinking not contradict with the fact that gravity, which surely exists, is the curvature of spacetime in...

Homework Statement find the transformation that turns this metric: ds^2=-X^2dT^2+dX^2 into the minkowski metric: diag(-1,1). The Attempt at a Solution attempt 1: I transformed the above metric into the coordinates that use the lines that define the light cone as the axes. Namely, u=T+ln(X)...

A map suggests that Atlanta is 730 miles in a direction of 5.00 degrees north of east from Dallas. The same map shows that Chicago is 560 miles in a direction of 21.0 degrees west of north from Atlanta. Modeling the Earth as flat, use this information to find the displacement from Dallas to...

I know that the water vapour condenses once it hits the colder air above. What I don't understand is why the warm-colder boundary is always parallel to the ground even while the masses of air are pushing through it. Why wouldn't the rising mass of moist air also determine warm-cold boundary...

Homework Statement On flat, leaned, surfaces, there are channels (rillenkarren), which are made by dissolution by rainwater (http://mafija.fmf.uni-lj.si/seminar/files/2005_2006/rillenkarren.pdf - not very important). They are 2-3 cm wide and around 0.5 m long. The formation is not yet known...

Does anyone know where I can find a flat tiny speaker, let's say for arguments sake roughly the size of a quarter, that can produce a reasonably loud audible tone? Thanks! Ted

One thing I think is a little bit funny (among a lot of other things). All the time I have learned and heard that the world is round, and when I travel with aircraft I can actually se it is at last courved. But when planning long distance travels I understand that it is quite round as it is...

I am really confused. Would you please tell me what the turbulent boundary layer thickness is on a flat plate? There is a well-known Schlichting formula in the previous editions of his book “boundary layer theory”, which is: \delta = 0.37 X Re^{-0.2} But actually I could not find this...

Can anyone help with how to find the analytical solution to problem involving finding the stress concentration around a circular hole in a flat plate. The plate is has tensile load on both sides.

Homework Statement A population of sources in a flat matter-dominated universe has a number-density n_0 at the present epoch and a monochromatic luminosity P(\nu) \propto \nu^{-\alpha} at frequency \nu. Show that the flux density S(\nu_0) observed at the present epoch from a source at redshift...

I want to be able to generate pages from a database but the data only changes occasionally. It'd be more efficient to have the pages served up from flat HTML most of the time and only have to "publish" to HTML when I make a change to the database. Is there a really convenient way of doing...

Interpretation: The Cosmic Background Radiation is evidence of a flat universe. Problem: How does a teacher show that all the knowledge necessary for this interpretation does not require the assumption of a flat universe?

What does it mean for the universe to be globally flat, What does it mean for the universe to be globally flat, spherical or hyperbolic? How does it relate to whether the universe will recollapse, or never stop expanding, or expand at an accelerating rate? How does it relate to local...