# All Questions

2k views

### Magnetic field insulators

I was wondering if there is any way to stop the magnetic field, without having the insulator turned into magnet. Let me present this as a simple case, there is a magnet to the left and a piece of iron ...
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### Magnetic Field at center of solenoid - Is this correct?

I've seen some different ways to compute tha magnetic field at the center of a solenoid, and sometimes people say that the result $B=\mu_0 n i$ is just an approximation. Well, I've thought on this way ...
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### Relationship between current, voltage, magnetic field in a torus

I'm trying to find the relation between current density $\boldsymbol{j}$, voltage $v$, and magnetic field $\boldsymbol{B}$ for the time-harmonic approximation in a cylindrically-symmetric coil (a ...
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### How would you swim in inviscid water?

The viscosity of water creates drag on swimmer's body so its effect is to slow down the swimmer. However the viscosity seems to be essential for pushing the water backwards by the swimmer's arms and ...
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### Water pressure on slanted wall

Water pressure is simply $pgh/2$ for a vertical wall parallel to the depth of the water at exactly the half the water's depth. Suppose the wall is tapered (angled) slightly at around 2 degrees from ...
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### How to estimate the physical size of a molecule?

I'm reading some chemistry-related papers that employ concepts of droplet evaporation. Since I am no chemist, I am wondering: How can I estimate the actual size of a molecule, say succinic acid? An ...
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### reflection at speed of light when both mirror and viewer is travelling at the speed of light [duplicate]

consider me sitting on the top of a train which is travelling close to the speed of light, will I be able to see my image on a mirror which I'm holding in my hand??
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### Vaporizing ethanol from liquid

What is going on here http://youtu.be/LQFmKPA-iAg Is ethanol leaving the liquid? If so, why? Does the pressure add energy to the ethanol molecules causing them to gasify and move rapidly near border ...
205 views

### The Hamiltonian for clocks?

I am rather a theoretician and looking for a formalism to represent biological clocks by Hermitian operators. The simplest thought model I am looking for is a formal representation of a clock (for ...
143 views

### virtual air-surface temperature difference above a water body

I'm trying to work through the equations for the following paper: http://onlinelibrary.wiley.com/doi/10.1029/2009JD012839/abstract and am trying to understand the concept of virtual air temperature, ...
293 views

### How to cut a stone on a White Dwarf?

I've heard that white dwarf stars are extremely dense and hard. So, if I had a piece of white dwarf matter, would it be possible to cut it (or otherwise) into a custom shape? How could one do that?
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### Calculating rotor torque out of mass center

Suppose I have an engine with propeller. I know there is aerodynamic force pushing the propeller opposite direction the engine is turning it. One component of this force is creating lift, but second ...
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### How does irradiance behave over time?

I am trying to clarify data on weather from the Royal Netherlands Meteorological Institute (KNMI); I have incorporated the Solar Position Algorithm (SPA), such that I can calculate sunset and sunrise ...
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### If the measurement of the proton size is correct and it is lower that it was expected than what are the theoretical implications?

In the press release of the recent measurement of the proton structure, they barely mention various theoretical explanations for the effect. What is the most likely (not assuming now that the ...
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### Is a proton collision (collisions like in the LHC) visible to the human eye?

I was curious if a proton collision is visible to the human eye. (This might sound like a really basic question and forgive me if it is. I am very inexperienced in Physics and just wanted an answer ...