# Search results

1. ### I General solution of the hydrogen atom Schrödinger equation

Thank you! But why is it that ‚the velocity you are trying to define has nothing to do with any velocity that could has been ascribed to the particle prior the first position measurement‘? Is that only a problem arising due to measurement ‚inperfection‘? This would be unsatisfying.
2. ### I General solution of the hydrogen atom Schrödinger equation

Thank you, this is helping me a lot! But I don’t understand another thing: If I measure the energy of an electron, how do I know in wich state (e.g. a superposition of eigenstates) it was before? For example: Could it be that a single electron in hydrogen is in a superposition of 1s and 2s...
3. ### I General solution of the hydrogen atom Schrödinger equation

Hello everyone! I have two questions wich had bothered me for quite some time. I am sorry if they are rather trivial. The first is about the general solution of the hydrogen atom schrödinger-equation: We learned in our quantum mechanics class that the general solution of every quantum system is...
4. ### B Gravitational force between two masses

Thank you all, I think I do understand!
5. ### B Gravitational force between two masses

Thanks for the awnser. But why not? Isn’t the force on m1 the same as on m2 because of Newton’s third law? Thank you!
6. ### B Gravitational force between two masses

Thank you! But would this mean, that the following is true: So let’s say, that we have two masses m1, m2. Mass m1 is accelerated toward m2 with a magnitude of $$a1=G\frac{m2}{r^2}$$ And then also m2 would be accelerated by $$a2=G\frac{m1}{r^2}$$ So the acceleration of the approaching of both...
7. ### B Gravitational force between two masses

Hello everyone. Probably this question is trivial, but nevertheless I am confused about newtons law of motion: $$F=G\frac{m_1m_2}{r^2}$$ Now, some sources say, that F is the force between the two masses m1 and m2. Other sources say, that F is the force that m1 exhibits on m2. But isn’t this a...

Thank you!

Yes, that’s absolutely right. I have a mistake in my calculation above. So here is what I think: Let’s talk about only one sort particle: H=U+pV=ST-pV+N##\mu##+pV=ST+N##\mu## So if H is really ST+N##\mu## than d(H-ST-N##\mu##)=0 This is true because of Gibbs dulem...

I have also ignored it in the definition of H=U-pV. U has the chemical potential in it. If I make the calculation with the chemical potential from the beginning on I get: d(H-TS)=Vdp-SdT-N##\mu## wich is zero.

But Vdp-SdT=0 because of the Gibbs Dulem relation (I am ignoring the chemical Potential)

Thanks! In my thermodynamics lecture notes, I can not find a indication that this only applies if T and P are constant. It is derived in a similar way like here: https://ps.uci.edu/~cyu/p115B/LectureNotes/Lecture6.pdf Edit: Could following be true: If H actually is TS than it follows...

Thanks for your awnser! I know that the integration is in general not that trivial, but in this case it is. This is due to eulers homogeneous function theorem. See the Wikipedia article (https://en.wikipedia.org/wiki/Internal_energy) in section ‘internal energy of multi component systems‘.

Hello everyone! I have a course in thermodynamics this year, and there is a question about enthalpy that I cannot answer: given the definition of enthalpy H=U+PV and the integral form of the internal energy U=TS-PV we conclude that H=TS. We normally say that enthalpy equals the heat exchanged in...
15. ### Problem in solving differential equation

Thank you very much, this is helping me a lot! Unfortunately I am very inexperienced in this topic. At one hand, the step size 10^6 would be optimal from a theoretical standpoint (the Lorenz section would (if plotted in the right way) represent a u-sequence). On the other hand result of stepsize...
16. ### Problem in solving differential equation

Hello everyone! I was studying chaotic systems and therefore made some computer simulations in python. I simulated the driven damped anhatmonic oscillator. The problem I am facing is with solving the differential equation for t=0s-200s. I used numpy.linspace(0,200,timesteps) for generate a time...
17. ### I Rosetta orbits and phase space

I really thank you for your helping hand! I had a bit of trouble but I think I worked it out: My posted equation is a first order differential equation. But if I use for example lagrange, I get a second order equation for r. I reduced it by considering energy conservation to the first order...
18. ### I Rosetta orbits and phase space

Thank you for the help! In the summer I read a book about nonlinear dynamics and there the term phase space was used in this context. So sorry if i was on the wrong page! But nevertheless I think, I have found the problem in my calculation: There is a square root in my r equation, so no point...
19. ### I Rosetta orbits and phase space

And exactly this is my problem. If I try my derivation with another potential (which is not time dependent) I get a solution of the same kind wich is not time dependent either. I don’t understand how this is fitting together.
20. ### I Rosetta orbits and phase space

Thank you for the answer! I have calculated following system of differential equations for the kepler problem (I am not sure if all prefactors are right, I don’t have my notes with me): If I put in the same coordinates r and theta I always get the same velocity. What am I misunderstanding?
21. ### I Rosetta orbits and phase space

When it is on the same spatial location (and has same mass, momentum and energy) it has to follow the same trajectories. This is because the velocity vector at this location points in the same direction. So if a trajectorie in a two body problem crosses itself at a later time and goes in a...
22. ### I Rosetta orbits and phase space

Thanks for your answer! But nevertheless: I could plot it like a vector field in a plane. And there should be no intersection, because that would violate uniqueness. Or to say it another way: If the trajectories don’t cross in 4D, then I cannot ‘reduce‘ it to a 2D vector fiel with constant...
23. ### I Rosetta orbits and phase space

I think that’s a definition ( at least I read it differently from different sources). Some would define a 2D phase space with a vector on every point, some would define a 4D phase space with 4 axes and no vectors. The result should be the same?
24. ### I Rosetta orbits and phase space

You can take x and y or r and phi, but it should be planar coordinates. On every point in this field there is a vector giving the velocity.
25. ### I Rosetta orbits and phase space

I was recently working on the two body problem and what I can say about solutions without solving the differential equation. There I came across a problem: Lets consider the Kepler problem (the two body problem with potential ~1/r^2). If I use lagrangian mechanics, I get two differential...
26. ### I The Trapping Region of the Lorenz equations

Thanks for the answer! So I thought that there is only one Liapunov function for a system. Like if i have a conservative system I can use a energy function to do the same things (and the Energy function is unique?). A liapunov function is a generalised energy function (at least so I was told)...
27. ### I The Trapping Region of the Lorenz equations

But why? With both methods I can get a minimal region, which is a trapping region. Because it is minimal, it has to be the same?
28. ### I The Trapping Region of the Lorenz equations

Yes that’s right, but on the edge of the trapping region all arrows should point inward (or at least be tangential to the boundary), so dr/dt should be less or equal to zero?
29. ### I The Trapping Region of the Lorenz equations

I was dealing with nonlinear systems of differential equations like the Lorenz equations (https://en.wikipedia.org/wiki/Lorenz_system). Now there is a trapping region of this system defined by the ellipsoid ρx^2+σy^2+σ(z-2ρ)^2<R. I wondered how this region is found and I found out that a...
30. ### I Confusion about position state kets

Thank you very much! I think I understand it. So the x is a Index and not the position itself. I could also use an index n if it’s continuous?