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Posted: 5/23/2003 6:36:59 PM EDT
[#1]
Quoted: IIRC, general relativity says that time is slower in stronger gravitational fields relative to weaker ones. If that's true then wouldn't the twin on the surface be younger? This was my understanding as well. If you fall into a black hole, everything seems to happen at normal speed to you. But someone watching you fall in from outside would see you stop at the event horizon and never pass in...at least that's what I have heard. I haven't studied general relativity at any quantitative level yet. |
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Posted: 5/23/2003 6:43:51 PM EDT
[#2]
Quoted: I was thinking today. (Not a common occurrence) I was thinking about physics, and gravitational acceleration. Well, I believe it all. In a vacuum, if you drop a feather and a bowling ball from the same height, they will hit at the same time. But I think there is another variable left out. It may be small, but it can still be a player. IIRC, I was taught that all objects, no matter how massive, have gravity. A pencil has gravity, however it is not powerful enough to attract anything. Even the moon only has a small gravitational force. So my question is: Wouldn't this variable affect acceleration (i.e. the larger object accelerates faster because it's own gravitational pull is combined with the Earth's.)? Obviously the difference would be so small between a bowling ball and a feather in gravitational pull that no instrument could measure it, but if these principles are applied in astronomical uses, where things happen on a massive scale, it could be a player. Am I thinking with my ass or am I the next Galileo? I didnt read all the post, but in a vaccum thy fall at the same rate, but in air the resistance is equal to the square of the velocity. {R= V²} therefor if it falls a 2 mph. the resistance is 4 mph. at 12 mph. the resistance is 144 mph. and so on. GG |
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Posted: 5/23/2003 6:44:48 PM EDT
[#3]
Zonan
Check out the book "A brief History of Time" by Stephen Hawking. My Physics I professor required it as a suppliment to help with the crazy stufff he would start chatting about even though it was way beyond our level. I covers the behavior of time and space at the event horizon of a black hole. It's a good read and it helps folks who can't, or are not good at thinking in the abstract, understand some of the more complex theoretical stuff. Basically everything is put into laymans terms. Very helpful to explain the complex stuff to non-physics types! |
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Posted: 5/23/2003 7:45:47 PM EDT
[#4]
Originally Posted By Gun Guru: Quoted: I was thinking today. (Not a common occurrence) I was thinking about physics, and gravitational acceleration. Well, I believe it all. In a vacuum, if you drop a feather and a bowling ball from the same height, they will hit at the same time. But I think there is another variable left out. It may be small, but it can still be a player. IIRC, I was taught that all objects, no matter how massive, have gravity. A pencil has gravity, however it is not powerful enough to attract anything. Even the moon only has a small gravitational force. So my question is: Wouldn't this variable affect acceleration (i.e. the larger object accelerates faster because it's own gravitational pull is combined with the Earth's.)? Obviously the difference would be so small between a bowling ball and a feather in gravitational pull that no instrument could measure it, but if these principles are applied in astronomical uses, where things happen on a massive scale, it could be a player. Am I thinking with my ass or am I the next Galileo? I didnt read all the post, but in a vaccum thy fall at the same rate, but in air the resistance is equal to the square of the velocity. {R= V²} therefor if it falls a 2 mph. the resistance is 4 mph. at 12 mph. the resistance is 144 mph. and so on. GG Wait a minute, something is wrong here. That would mean that the force of resistance is greater than the force of gravity and that the object is now rising. |
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Posted: 5/24/2003 11:36:02 AM EDT
[#5]
Originally Posted By Gun Guru: I didnt read all the post, but in a vaccum thy fall at the same rate, but in air the resistance is equal to the square of the velocity. {R= V²} therefor if it falls a 2 mph. the resistance is 4 mph. at 12 mph. the resistance is 144 mph. and so on. GG This is not true. The force due to fluid resistance is a complex function of velocity. v^2 is often used as a (very rough) approximation, as is v (for slow moving objects), but neither is correct. |
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Posted: 5/24/2003 11:40:30 AM EDT
[#6]
Quoted: Zonan Check out the book "A brief History of Time" by Stephen Hawking. My Physics I professor required it as a suppliment to help with the crazy stufff he would start chatting about even though it was way beyond our level. I covers the behavior of time and space at the event horizon of a black hole. It's a good read and it helps folks who can't, or are not good at thinking in the abstract, understand some of the more complex theoretical stuff. Basically everything is put into laymans terms. Very helpful to explain the complex stuff to non-physics types! But I am a physics type. I am surprised you were told to read Hawking's stuff in a college level physics course. His is very qualitative, which is mostly useless to aspiring physicists who must learn the math to be useful. At my university, books by Hawking don't even get mentioned--they just don't have much use beyond lending some understanding to laymen. I am a physics major if it wasn't obvious from my posts (particularly the "proof" that the acceleration of the two objects is the same but the time of contact are different using Newton's laws). |
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