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- Thread starter Shmi
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if you add some more conditions like speed of light etc ... well mass will eventually become significant

if you make them wave particles and use de broglies momentum of a wave ... maybe, but i dont think u'll find an answer other than infinity in classical physics

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Also, we would need to assume that the "stationary" particle is much more massive than the orbiting one. It might help to think in terms of a planet orbiting the sun, or of Bohr's hydrogen atom model.

EDIT added:

By the way, this statement makes little sense. A mass can be negligible only relative to another mass, not relative to a different physical concept like force, distance, time, etc....the mass is negligible relative to the electric forces at play...

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To keep this system at a constant radius (which I give to be ~Bohr radius of hydrogen atom), I want to find out how fast a classical particle would have to move to maintain this radius.

Am I crazy to equate the centripetal force and the coulomb's force? Here the units clearly match.

[tex]\frac{m_e v^2}{r} = \frac{kq_e^2}{r^2}[/tex]

Solving for

[tex]v = \sqrt{\frac{k q_e^2}{m_e r}}[/tex]

Which for given values produces a number around 2.1*10^6 m/s. Reasonable? More importantly, is this a reasonable problem to solve for other physics students fresh out of mechanics and just learning early electrostatics?

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Not crazy at all. That is exactly how centripetal force works; you equate it with the net force acting perpendicular to the particle's velocity.Am I crazy to equate the centripetal force and the coulomb's force?

By the way, you are basically solving the Bohr model of the hydrogen atom, except for the part where only discrete (quantized) orbits are allowed. I remember that the velocity of the ground state electron in Bohr's model is about 2 orders of magnitude slower than

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BruceW

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jtbell

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Am I crazy to equate the centripetal force and the coulomb's force?

No, because the centripetal force

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