Quantum Theory of Earth Satellite Analogy to Bohr Model

AI Thread Summary
The discussion focuses on developing a quantum theory of Earth satellites analogous to the Bohr model of the hydrogen atom, specifically deriving expressions for orbit radius and energy in terms of quantum numbers. A 1000 kg satellite in a 7000 km orbit raises questions about the appropriate quantum number and the use of the Rydberg constant, which is deemed unsuitable due to its electron-specific nature. Participants suggest utilizing the Sommerfeld-Wilson quantization condition for angular momentum, noting that the small Planck constant leads to large quantum numbers, making distinct orbits nearly indistinguishable. The challenge lies in adapting the equations to account for gravitational potential rather than electromagnetic forces. The conversation emphasizes the need for careful consideration of constants and parameters relevant to satellite dynamics.
Rapier
Messages
83
Reaction score
0
Problem:
In analogy to the Bohr Theory of the hydrogen atom, develop a quantum theory of Earth satellites, obtaining expressions for the orbit radius (r) and the energy (E) in terms of the quantum number (n) and the other relevant parameters. A satellite of mass 1000 kg is in a circular orbit of radius 7000 km, to what value of n does this correspond?

Equations and Constants:
Bohr Model: E = -R*h/n^2
E = 1/2 * m * r^2 * ω*2
ω = v/r
v^2 = G*M/r
R = 1.0973 x 10^7 m^-1
h = 6.626x10^34 kg*m^2/s
M = 5.972x10^24 kg
G = 6.674x10^-11 m^3/(kg*s^2)

Attempt:
E = -R*h/n^2
1/2 * m * r^2 * ω*2 = -Rh/n^2
r^2 = -2*R*h/(n^2 * ω^2 * m)
r^2 = -2*R*h*r^3/(n^2 * G* M * m)
1/r = -2*R*h/(n^2 * G* M * m)
r = (n^2 * G* M * m) / (-2*R*h)

Just by parsing the units I know I've taken a wrong turn. I've tried multiple times and I appear to be missing a velocity term somewhere with the (-2*R*h). I think I'm missing something simple, I just don't see it.

Thanks.
 
Physics news on Phys.org
Rapier said:
E = -R*h/n^2
If R is the Rydberg constant: the potential of Earth is not the same as the one of an electron in an atom.

Edit: I moved the thread to the homework section.
 
Last edited:
It's probably simpler in this case to use the Sommerfeld-Wilson quantization condition on the angular momentum of the satellite. You will find that since ##h## is so small compared to the other scales of the problem that the quantum number is huge and different quantized orbits are so close together as to be beyond distinguishing within the precision of the measurements that we could make.
 
mfb said:
If R is the Rydberg constant: the potential of Earth is not the same as the one of an electron in an atom.

Edit: I moved the thread to the homework section.

I'm not sure what to use for R then because my definition of R includes the mass of an electron and the charge. I can see replacing the mass of an electron with the mass of my satellite, but then what do I do with the charge? I tried to analyse the units to come up with a value but I got nothing that made any sense.

Oh, and thanks for moving it! :)
 
fzero said:
It's probably simpler in this case to use the Sommerfeld-Wilson quantization condition on the angular momentum of the satellite. You will find that since ##h## is so small compared to the other scales of the problem that the quantum number is huge and different quantized orbits are so close together as to be beyond distinguishing within the precision of the measurements that we could make.

Oh, that does look more promising. Let me give it a stab.
 
Rapier said:
I'm not sure what to use for R then because my definition of R includes the mass of an electron and the charge. I can see replacing the mass of an electron with the mass of my satellite, but then what do I do with the charge? I tried to analyse the units to come up with a value but I got nothing that made any sense.

Oh, and thanks for moving it! :)
You cannot use the Rydberg constant - it is specific to the electromagnetism problem in an atom. You can see how it is derived based on the potential energy, however, and use this with the gravitational potential instead.
 
Thread 'Collision of a bullet on a rod-string system: query'
In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
Back
Top