Classical Physics

How is Stefan–Boltzmann law posibble? How can be compatibile with energy conservation law?

I came across some interesting information about the element Bismuth: "No other metal is verified to be more naturally diamagetic than Bismuth. It is the most diamagnetic of naturally occuring elements." "Because bismuth is the most diamagnetic naturally occurring element, it is used for diamagnetic levitation." Can someone supply an understandable explaination, or a reference to an understandable explaination, as to why bismuth is the most diamagnetic of naturally occuring elements? And to make the question of more interest than the answer that one might be able to supply from a textbook: would molten (liquid) bismuth exhibit the same diamagnetic properties as is…

Hi all, It is said that liquids are mostly non compressible & gases are compressible. Could some one pls explain, do both require same energy to have same pressure? For example how much energy it requires to compress air of 1 m3 to 10 kg/cm2 & water of 1 m3 to same10 kg/cm2 Thanks.

We know that the 1st dimension is length (a line), the 2nd dimension is length + width (a polygon), the 3rd dimension is length + width + hieght (a cube), and the fourth dimension is length + width + hienght + time (a moving cube). Does anyone know what is the 5th dimension? Is it heat, colour, chemical properties or something like that? This is a serious matter to discuss.

Does anyone know the experimentally measured minimum distance where the inverse square law holds?

Lately i have seen people theorize that gravity is not a force and it is a natural motion because gravity pulls something instantly. Like if you were to drop something it does not have any delay before it starts to fall. And they have attributed this to proving it as a natural motion. But i would like to disagree and show my arguement. First, The object begins to fall instantly because the gravity is already acting on the object. So it does not delay because gravity is already pulling on it. But your hand is stopping it in the example of holding something in your hand. So when you let go the object instantly falls to the ground. Second, The effects of LOSS of gravity as o…

Hi, I m currently studying the Drude model. They are saying that the conductivity increase with the increase of the frequency. It s page 122 here. thanks

I though I might share this. It is Jimmy Sabori's rebuild of the Papp engine. It looks completely rediculous, and everything Sabori says is nonsense. http://stream.osen.org/aag/Noble-Gas-340.wmv There is an incredibly funny article by Richard Feyman on the original Papp engine demonstration, during which an unfortunate bystander is killed by the prototypes climactic destruction. You can read it here. More informatin can be found at this address: http://www.americanantigravity.com/articles/486/1/Sabori%26%2339%3Bs-Papp-Engine-Video

Hello scienceforums community. I'd like to introduce myself to start because I am somewhat of a new member. I am a physics undergrad but I'm very fresh into the realm of physics. I would like to ask some questions I've had about magnetism in order to give some better insight into what it is exactly. 1) Of course when talking about magnetism you have to talk about electricity. The equation B = {(mu)(I)}/ {2(pi)r} is an equation used to compute the magnetic field induced by a current carrying wire. I was curious to know what exactly mu (the permeability constant) represents in the equation and what makes it so important. 2) When calculating the strength of a magnet…

Hello friends, I have been thinking that when chemical reaction take place sometimes colour change may happen as new substance are formed.So what in atomic level decide the color of substance.Does the color of substance are decided by electron,proton or any other atomic particles.If these particles really does decide color,then how???

1) What is holding us against the Earth? 2) Why is it able to do so? 3) What interaction is there between matter and space? 4) How is it relevant to what is keeping us from being flung from the Earth? 5) What exactly is gravity? 6) Why is G found is both Einstein and Newtons equations? (curvature of space-time) = (mass-energy density) * 8 pi G / c4 Fg=Gm1m2/d^2 These are just a few questions to get the discussion going. I think this topic will clarify a lot of what was said in a different topic called "do objects fall at the same speed? no" or something close to that. The arguments mainly revolved around gravity so here is a chance to explain your …

I created this thread in order to demonstrate the usefulness of a sub forum on the philosophy of physics.<br /><br />The philosophy of physics obviously falls under general philosophy. The subject of falsifiability falls under the philosophy of physics. However it someone wishes to create a thread which falls under the philosophy of physics, then, as of now, it should e oosted in the general philosophy forum. Most physicists I know would never poke their nose into a forum labeled <i>General Philosophy</i>. And that includes the famous ones I know. However they just might poke their nose into a forum labeled <i>Philosophy of Physics</i>,…

Hi guys, I had a discussion with a friend about the Harrier jet and how far up it could go compared to the propulsion of the jet, and if we could calculate this mathematically. Before I go on, the Harrier jet is a pretty cool attack plane that can lift off vertically. See example here: Theoretically speaking, if instead of gas propulsion we had water jets going downwards (powerful ones) and we know the weight of the jet, we should be able to calculate at what distance above the ground the forces of the thrust from the propulsion equals the force of gravity from the plane's weight. So we could tell how far up it would go based on the initial pressure o…

Hi, My question should be simple enough: If (G*m1*m2)/distance^2 gives you the total amount of gravitational force, then how can I calculate the acceleration for each individual mass? I'm trying to write a simple simulation program, but I can't read some of the math that I've looked up. Any help is appreciated

Coulombs law is F=kq1q2/r^2, where F is the force of repulsion between two charged objects, r is the distance between them, q1 and q2 are the objects' respective charges, and k is a constant whose value is dependent upon the medium between the 2 objects. The larger k is, the greater the force, and the smaller k is the smaller the force. k is at its greatest in a vacuum. In contrast, in water it is an eightyth as large. In the body it is about eighth as large. In rubber it is about half to a third. Etc etc. My question is why? I suspect it might have something to do with induction.

A sailboat keel has a roundish leading edge and a somewhat sharp trailing edge. If both edges are made as sharp as a razor blade, setting aside the fragility of such edges; will the sharper keel have less drag ?

Hello everybody! I'm looking for publications (dissertations, articles in journals,... whatever is scientifically based) concerning the temperature between sliding surfaces. I need this information for my own bachelor's thesis and I need to calculate the temperature expected on the contact surface between two bodies. These two bodies will be rubbing against each other at high speed. Body 1 will be some defined steel, Body 2 will consist of the same steel coated with a thin film of some friction-reducing material. So what I am looking for is in the ideal case some formula, where I can put in my materials' parameters and get the contact temperature. But any public…

I'm curious whether or not it is possible to make a vacuum by taking a rigid, hollow sphere and forming a vacuum inside of it. Presumably this is possible if you just assume the material it is made out of is infinitely strong and rigid (it just needs to weigh less than the equivalent volume of air). However, I'm curious if this is possible with any materials we know about.

Hi,I just wonder if i can make a little device which can turn laser into energy？and of course i know MIT just using magnetic filed to transport the energy,but it was too complex to me,and can sb. give me some data,all i want to do is just let my POV system work by using laser as power solution. POV is short for Persistence of vision , and the whole system including a low voltage MCU（3V）,60 LEDs and some other components. Any information is welcome.

I'm a little bit confused about this...i know that when a current-carrying conductor is placed in a magnetic field, it experiences a force called Lorentz force, this is the formula: F = Bil but the thing i can't understand is whether this FORCE is perpendicular to the magnetic field or the magnetic field is perpendicular to the CURRENT? by the right hand rule, i can see easily that the magnetic field is perpendicular to the force, but in some books and examples it says that the current must be perpendicular to the magnetic field for applie…

Hi. A plain magnet, fully isolated from the seawater it is immersed in; as inside a plastic hermetic box. The magnetic field is present in the seawater. Now one of these things happen: Either the magnet is made to spin or move, or the seawater is put to flow around it. Does the electrically conductive seawater experiences an electric current in the vicinity of the magnet ? If there is no motion at all relative to each other, will there be no electric current ?

Those clever experiments developed by scientists along the years, as light spectrum on a prism, resonances, beam interruption wheels, mercury barometer column, magnetic induction, Millikan's, and many other share great lucidity in their conceptions. How would you design a clever experiment to measure the propagation speed of gravity ?

Hi. I learned somewhere that sun radiation (heat + light) passes trough glass as in a window, but the heat does not escape again towards the outside trough the glass, bouncing back and getting trapped indoors as in a greenhouse. I have trouble understanding the effect; does it mean an item enclosed in a glass jar indoors will not get warm as the heat will not pass trough glass again ? (except the amount of heat transferred by convection from room air to jar)

Hi. The temperature of the air along the path of a lightning bolt rises to many hundreds of degrees in about a tenth of a second; is that correct ?

Here's a problem I thought of that I found a solution for: Problem: How long does it take for a person on the surface of the Earth to communicate with someone else on a different point on the Earth, assuming a fibre optic link and using circles with circumscribed polygons? Or: How long does it take light to travel 1/2 way around the Earth? Solution: Find: t in s Given: c=3E8 m/s, mean rE=6.37E6 m s=vt, t=s/v CE=2(pi)rE, 1/2 CE=1/2(2)pi(rE) t=s/v=(1/2)CE/c=pi(rE)/c=3.14(6.37E6 m)/3.00E8 m/s=0.07 s = 7/100 s