# All Questions

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### Non-linear dynamics of classical hydrogen atom

I'd like to know if there have been attempts in solving the full problem of the dynamics of a classical hydrogen atom. Taking into account Newton equations for the electron and the proton and Maxwell ...
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### What does the wind speed have to be to blow away a person?

With the approaching hurricane, I am curious about what would happen if I go outside, in particular whether the wind gusts might be fast enough to blow me away. How fast would the wind have to be to ...
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### Kinetic Energy of Stone

If a stone is launched upward, of which is subject to gravity and air resistance, which of the following will have a greater kinetic energy? The stone at a point on its way up, or the stone at the ...
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### If nothing in the universe can travel faster than light, how come light can't escape a black hole? [duplicate]

Possible Duplicate: How does gravity escape a black hole? If nothing in the universe can travel faster than light, how come light can't escape a black hole? I mean, Einstein's relativity ...
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### Why does a tire need to be filled with air?

The Mini 4WD's tires aren't full of air, and it can run. Also, the tank doesn't have tires with air. So, the question is: why do real cars on the road need to be filled with air? What is the idea ...
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### James Webb Space Telescope's halo orbit at Lagrange point L2

The James Webb Space Telescope (JWST) is expected to be launched in 2018 and operate in the L2 vicinity, about 1.5 million km from Earth. It will be placed in a halo orbit around the unstable L2 ...
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### Maximum Kinetic energy of a spring

The block in the figure below lies on a horizontal frictionless surface and is attached to the free end of the spring, with a spring constant of 35 N/m. Initially, the spring is at its relaxed ...
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### Solving a system of PDE equation in mathematica using a steady-state and time-evolution method [closed]

I'm working to solve the steady-state short circuit current of a solar cells, using the coupled continuity equations with a drift-diffusion expression and Poisson's equation: ...
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### Bandgap Spacing in Photonic Crystals

I am doing some self-study on photonics and have encountered the following question: We know that amorphous electronic crystals such as amorphous silicon have a bandgap. Can amorphous photonic ...
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### materials that repel positrons?

In this article is discussed at some length positron formation in metallic surfaces. Positrons have work functions that describe how much energy they have to receive in order to be extracted from the ...
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### When and How far out will the Voyager twins come to a full-stop?

So space is mostly, but not entirely, empty. Every few (dunno the order) cubic metres of space there is some cosmic dust. Assuming that Cosmic dust exerts some friction on passing bodies, The ...
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### Faster than light due to reference position [duplicate]

Possible Duplicate: Travelling faster than the speed of light Please try to follow and clarify me I've been curious about this for a long time as it seems a bit paradox due to the rule that ...
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### When and how do you represent a two body state as a tensor product?

I have read that in quantum mechanics, compound systems are constructed as tensor products. But on page 177 of Griffith, for example, a two body wavefunction is introduced as Psi ...
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### Quantum phyics project for a high schooler [duplicate]

Possible Duplicate: Study Quantum Physics I am a high schooler who is interested in physics and mathematics, and I have a kind of 'high-school thesis' coming up in a year and a half or so. ...
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### Why do we use Root Mean Square (RMS) values when talking about AC voltage

What makes it a good idea to use RMS rather than peak values of current and voltage when we talk about or compute with AC signals.