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Apr
7
comment Calculating the most probable radius for an electron of a hydrogen atom in the ground state
We use area because we want the probability that r is exactly 0.1 nm (technically probability density), not the probability that r is less than 0.1 nm.
Apr
7
comment Thomson's jumping ring experiment
Yes the ring will move toward (be attracted to) the field when the flux drops, but the ring will tend to repel more than attract overall (the explanation is complex, however). See youtube.com/watch?v=dw73DcwIX-A for a similar example: you get more repulsion on average.
Apr
7
revised Calculating the most probable radius for an electron of a hydrogen atom in the ground state
added 75 characters in body
Apr
7
comment Thomson's jumping ring experiment
At 60Hz it will levitate in a relatively fixed place. The current is constantly changing. Each "pulse" causes a repulsion of the ring.
Apr
7
answered Thomson's jumping ring experiment
Apr
7
answered Calculating the most probable radius for an electron of a hydrogen atom in the ground state
Apr
7
revised Dyson air blade principle as a propulsion system for an autonomous underwater vehicle?
added 173 characters in body
Apr
7
answered Dyson air blade principle as a propulsion system for an autonomous underwater vehicle?
Apr
5
comment How can super massive black holes have a lower density than water?
The water pool would pack more mass into a similar size of space the our BH, so the whole thing collapses into one giant BH immediately.
Mar
27
answered Do I need to take both particles' momentum into account in photoelectric emission?
Mar
21
comment Small object in air
Your drag equation assumes "inertial" drag, but "viscous drag" is more important at this tiny length scale. See en.wikipedia.org/wiki/Stokes'_law.
Mar
16
comment Primordial black hole: how dense does matter need to be to feed it?
The problem with a simple event-horizon-drain argument is that the accretion heat generated and/or the Hawking radiation would push matter away, counteracting the gravity. What rate of accretion before the heat generated produces a "bubble" that prevents other matter from entering? I don't know.
Mar
16
revised Primordial black hole: how dense does matter need to be to feed it?
added 86 characters in body
Mar
16
asked Primordial black hole: how dense does matter need to be to feed it?
Mar
1
awarded  Organizer
Mar
1
revised Two masses collide on a ramp
Added hw tag.
Mar
1
suggested suggested edit on Two masses collide on a ramp
Feb
27
comment Is “dark clothes for winter, light for summer” relevant?
With light skin a white t-shirt helps (personal experience). However, the black robes in the desert don't affect heat gain because they are so thick and loose fitting.
Feb
27
revised Effective mass of a black hole?
added 16 characters in body
Feb
26
comment How would a black hole power plant work?
How could you accelerate the black hole?