Recent content by Aero

Time-independence of a physical system, only requires the square modulus of the wavefunction to be time-independent, not the wave function itself. This means that the wave function itself can vary with time, although only in a way that does not change its sqaure modulus, which means that it can...

This is only true for partial differentiation. However, here we are dealing with normal differentiation and integration. By your logic, d/dy (x) = 0 because you would treat x like a constant. But this is plain wrong: d/dy (x) = dx/dy.

But when you differentiate with respect to y, you get d/dy (xy) = x + y * dx/dy and x is not treated as a constant, so why should it be treated as a constant in integration?

But isn't this temperature irrelevant, because light of any "temperature" will heat something up, no matter what the temperature differential?

No, because x is not a constant. Consider d(xy). Because x is not a constant this is not just xdy.

You are wrong. Remember Newton's third law. There are two forces here: the man pulling down on the rope, and the rope pulling up on the man. The former is the force in his muscles, and the latter is the tension in the string. If the man exerts a 10N force downwards on the string, the string...

How can radiation have a temperature? Radiation is just electromagnetic waves, but temperature only refers to the level of thermal vibrations in matter.

Almost: you have a rounding error in the final answer.

Did you mean \left( {x + y - 4} \right)dy - \left( {2x - y + 1} \right)dx = 0 ? If so then you have neglected some products. On the left, \int {xdy} \ne xy and similarly on the right.

This all depends on what you consider obvious. Newton considered it obvious that F_total = F1 + F2 + ... And therefore for him it definitely was a law, to say that F = dp/dt. But the modern view is that it is silly to think something like the fact that forces are additive obvious before...

\frac{{d^2 y}}{{dx^2 }} + \left( {Ax + B} \right)y = 0 I have tried lots of substitions, but a solution won't pop out. Can anyone help solve this? Thanks.

If a string is lying in the x-axis with a tension of T, is the stress tensor \sigma = \left( {\begin{array}{*{20}c} T & 0 & 0 \\ 0 & 0 & 0 \\ 0 & 0 & 0 \\ \end{array}} \right) If you feed in a normal vector to this, it should give you the tension on the associated...

A temperature differential is only required for heat conduction. WIth a solar cell, you are getting heat energy by radiation.

When you try to "solve" a problem, you are trying to find the wavefunction after a certain time t, given the initial wavefunction, right? Why does finding the energy eigenstates help? In other words, why do we only look at "steady state" problems? Suppose I wanted to model a particle moving...