Flat Definition and 469 Threads

1. A 10 kg box on a level surface is attached by a weightless, unstretchable rope to a 7.0 kg box which rest on a 30 degree incline. Find the rate of acceleration and the tension in the rope if... a) there is no friction ... b) coefficient of friction is 0.10 for both boxes 2. F_net...

A curved space and be flattened out locally, giving a flat "subspace" while increasing the curvature around that "subspace", right? If so, wouldn't it be possible to make any curved space flat everywhere and concentrate all the curvature at a single point and move that point infinately far away...

If geometry of spacetime is flat in intergalactic medium (empty space), why then there is no point of asking where is the center of Universe?

Why does Saturn's dust form a flat ring and not a sphere around it?

1. The present universe is observed to be flat. Was it always flat, before it started its accelerated expansion? 2. Is the Riemann tensor zero for this flat universe? Is its geometry that of special relativity? I'd appreciate if Marcus or Ich or any other science advisor weighed in on...

Homework Statement We have a tank of air at 7 atm, 30 L, and 293 Kelvin(20 Celsius), and a flat tire with 1atm, 10 L (Constant), also at 293 K (20 C). The valve is opened quickly and closed quickly when the pressure in the tank reaches 6 atm. Using the Ideal gas assumption and taking the...

If there is topic "Is Our Universe Flat" poin me. I bet:) no

I'm trying to make a computer simulation of ship. Currently I'm working on a force of wind on the ship sail. This is the page which describes the basics: http://www.animations.physics.unsw.edu.au/jw/sailing.html Basicaly, wind (W - vector) has some staring direction and then that...

Rencently, I found myself confused by some fundamental concepts in GR. I hope someone can help me with that. We all know the vacuum Einstein equation (VEE) without the cosmological constant \Lambda is Rab=0. Since I learn GR the words " matters bend the spacetime " been told again and...

http://theflatEarth'society.org/forum/index.php?PHPSESSID=61505d6b5883a9d597b57940b118119b&topic=13876.0

The size of bouncing lumps of charged particles, DM and photons in the primordial universe is supposed to be around 220,000 lyr (= sound horizon since the acoustic speed is approx 0.6c). If we then calculate the angle A subtended at Earth by a lump of this size W, some 13.8 Glyr away D (back at...

There is a scientific word/explanation for the phenomenon that a out and back course in a cycling time trial race can actually be faster than a flat course. For example, in Cherokee Park in Louisville, there is a 10 kilometer course that starts on the flats, then has a pretty good downgrade...

1.A hurricane wind blows across a 7.8 m x 12 m flat roof at a speed of 180 km/hr. What is the pressure difference? How much force is exerted on the roof? 2. Homework Equations P= p_atmos + pgd P=F/AThe Attempt at a Solution p = 101300Pa - (1.3)(9.8m/s^2)(93.6m^2) p = 100107.5Pa 100107.5Pa =...

So, I now understand based on things that I have read, and things that people on this forum have told me, that the universe if flat, must be infinite. My question is, when we look into the farthest reaches of space, we see a small, finite baby universe. How is this possible? The universe can...

Homework Statement A car of mass M = 1200 kg traveling at 40.0 km/hour enters a banked turn covered with ice. The road is banked at an angle theta, and there is no friction between the road and the car's tires. What is the radius r of the turn if \theta = 20.0 degrees (assuming the car...

I know this is a commonly adressed topic, but it is one in which things are hazy to me. If the universe is finite (which we don't know), and flat (which we are becoming ever more increasingly certain about), then how could a light beam fired from a point in the universe not ever reach its...

For understand general relativity, they tell me, there have flat space, add a sun, the flat space changed to curved space, so the Earth move around. There has a question, if we admit mass, space , time is created, how could exist flat space? there have space-time and there have nothing?

[b]1. The problem statement: a 100kg homogeneous cylinder of radius .3m. Starts at rest. Is pulled by a string wrapped around the cylinder coming off the top with a force of 500N. Find the angular velocity after the cylinder has rolled one revolution? The attempt at a solution: I=...

If someone were to remove all of the gravitational influences on a portion of space would that essentially make that portion of spacetime flat? (Just curious):-p

Homework Statement Two optically flat plates of glass are separated at one end by a wire of diameter 0.250 mm; at the other end they touch. Thus, the air gap between the plates has a thickness ranging from 0 to 0.250 mm. The plates are 15.0 cm long and are illuminated from above with light...

How do you take the moments of inertia of a flat body? I know howto take it if it's a 3d body. And the 2d case should be really simpe,but I'm too stupid to figure it out. Can you help me? For example.. Say we have a body that's a rectangle of mass m on |x| < a, |y| < b..? Thanks so much.

Homework Statement A car, mass m=2500kg, rounds a curve on a flat road at a speed v= 15 m/s. The radius of curvature of the curve is r= 60m. There is obviously (static) friction between the road and the car tires, or the car would not stay on the curve. Homework Equations a.)...

Hi gang, I've been reading for a while and now need some help of my own. Thanks in advance. I'm currently planning a project where I'm going to demonstrate a launch of an RC car off the flat roof of a building. The height of the roof is 25'. I figure the RC car will go 25mph, and the ramp...

Is it possible to define gravitons corresponding to flat spacetime? If so, how? Flat spacetme has zero curvature. How does one mathematically describe gravitons for flat spacetime?

hi to everyone! i want to ask that, why it is easier to swing a linear flat stick rather than any other heavy stick or a baseball stick ? what is the reasion of this question in physics point of view?

http://www.news.cornell.edu/stories/March06/CMB_Timeline300.jpg If space-time is flat (on large scale), why then does this [above] picture show curves? Would I be right to say that space time at anyone moment is flat but over time it is curved?

Hi there, I am a physics idiot, but I still want to know where my object will end up ;) Here is what I am trying to do: I have a block that is sliding on a flat surface. I know the friction coefficient, the mass of the block, its initial position, gravity and initial velocity. How...

Hello everyone; here is the problem that I’m currently working on: =============================================== a- Find the principal moments of inertia of a flat rectangular plate (mass = 30g, a = 80 mm, b = 60 mm) that rotates about a diagonal with velocity ω = 15 rad/s. b- What are...

1.a) Concider the 2-space consisting of a spherical shell at constan radius, r. In polar coordinates the line element on the surface can be written (a, b,∈ 1,2) Homework Equations ds2=gabdxadxb=r2dθ2+sin2θdφ2 calculate gab, Γabc, R1212, R2121, R11, R22, R The Attempt at a Solution...

I have been reading John Baez's introduction to General Relativity (http://math.ucr.edu/home/baez/einstein/einstein.pdf). This part got me thinking: My question is, in order to completely model our universe's (3+1)-dimensional spacetime as a manifold in a higher-dimension, flat spacetime, how...

Homework Statement Imagine the Earth is indeed not a sphere of radius r, but an infinite plate of thickness H. What value of H is needed to allow the same gravitational acceleration to be experiences as on the surface of the actual Earth? (Assume the Earth's density is uniform and equal in...

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...

[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...