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location Baltimore, MD
age 30
visits member for 4 years, 6 months
seen 1 hour ago

I'm a physics graduate student.


5h
comment Black Body Golf Balls
No, the answer does not contradict itself. It discusses two scenarios: one in which the golf ball has exactly the same cross section as the sphere, and one in which the golf ball starts out the same as the sphere and has dimples added. Since those scenarios are different, they have different answers. The cross section determines what radiation is absorbed from the shell because it determines what lines of sight from the shell are blocked by the sphere. I don't understand how this isn't obvious.
13h
comment Black Body Golf Balls
The cross section of an object determines what radiation it absorbs from the shell. I find this to be extremely obvious and do not see how it would be possible for you to fail to understand it. Your statement about "cross-sectional surface area (perimeter)" is very confusing. I don't know what you mean by that. I am referring to the cross-sectional area because it determines how much radiation is absorbed from the shell. I am not discussing the perimeter or the surface area.
13h
comment Black Body Golf Balls
Based on your comment, you are clearly unwilling to read my answer carefully; I said very, very plainly in my original answer that if you start with a sphere and add dimples, the emitted radiation will go down very slightly. Your denial of that means you are not truly attempting to understand what I wrote.
13h
awarded  Electorate
13h
comment Black Body Golf Balls
Suppose the sphere absorbs power $p_s$. Then, in order to remain the same temperature, it must also radiate power $p_s$. Because the golf ball is very nearly the same shape and size as the sphere, it absorbs very nearly power $p_s$, and so it emits very nearly $p_s$, so the golf ball and sphere emit and absorb very nearly the same power. The only difference is that adding dimples actually makes the golf ball's cross section very slightly smaller so it absorbs/emits slightly less than $p_s$. A very small sphere would absorb much less than $p_s$ and so would radiate much less.
13h
comment Black Body Golf Balls
I will have to guess at what you're saying because it is extremely difficult to understand you. My best guess is that you have completely ignored the crucial part of my argument - that the golf ball and the sphere absorb the same amount of radiation as each other because they have the same cross-section. A small sphere clearly does not absorb the same amount of radiation as a large sphere, so the argument in my answer does not indicate that a small and large sphere would radiate the same amount as you appear to be implying.
14h
comment Black Body Golf Balls
I can't tell what you're asking, sorry. My answer provides a complete explanation of why the golf ball will not radiate more energy. What specific part of it do you not understand? Your question about a ball of smaller radius is a non-sequitur to me. Yes, a smaller ball will indeed remain at the same temperature, but I don't get why you care.
15h
answered Black Body Golf Balls
1d
revised Does my mass really affect objects on the other side of the universe?
edited title
May
18
comment How does the kinetic energy of a ballerina increase?
physics.stackexchange.com/q/3611
May
18
comment How does the kinetic energy of a ballerina increase?
possible duplicate of Ice skater increase of energy
May
13
awarded  quantum-mechanics
May
12
awarded  Nice Answer
May
12
comment Potential of an infinitely long cylinder
In reply to "work done by the electric field", you are not reading the entire sentence. It is the work done in taking the charge out to infinity. The further out you are from your cylinder, the less work done in taking the charge to infinity, so the potential goes down.
May
12
comment Potential of an infinitely long cylinder
The point is that energy is conserved. When the E-field does work on a particle, the particle's kinetic energy goes up and its potential energy goes down by the same amount so that the total energy stays the same.
May
12
answered Potential of an infinitely long cylinder
May
12
answered If two kets are each orthogonal to a third ket, are they also orthogonal to each other?
May
10
revised Is there any upper limit on a particles kinetic energy?
deleted 1 character in body; edited tags
May
3
revised How does a hovercraft hover, if it has low pressure underneath it?
rolled back to a previous revision
May
3
comment How does a hovercraft hover, if it has low pressure underneath it?
I don't know, sorry. Wikipedia is usually a good first place to look.