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can't plug one into the other when they do not correlate.... different concepts.
I've seen a whole 700 chem class struggle with that concept last semester. which reminds me of the arguments here. |
Don’t bring up chemistry, next we will be talking about moles…
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Well then if we're discussing gravity we need to start talking about one of my favs the meter/second/second...weeeee! Oh oh how about Newtons kg-2 m2?
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Or imagine a planet of 100% water, with the block of steel at the center. What would be the big gravitational force on that block of steel, and which way would this gravitational field accelerate that block? ;) Quote:
Back to the ocean thing... If, as an engineering exercise, the questions arose of, how much force would be needed to suspend a 100_lb ingot of Aluminum in a freshwater lake? would you answer 100_lbs ? Yeah, you probably would. -LOL But would you show your work... SG<sub>Al</sub> = 2.6, Suspension Force = 100-(100/2.6)= 61.54_lbf Buoyancy Force = 100/2.6 = 38.46_lbf Total Force = Buoyancy Force + Suspension Force = 100_lbf Or would you leave those details of the answer hanging until your teacher marked "100_lbf" wrong? Not that I would ever do anything like that. :cool: |
Pop quiz.
What’s the value of gravity of the center of the earth? |
Are we assuming a static spherically symmetric perfect density?
And/or do you mean center of mass? |
No, I mean the gravitational constant at the center of the earth.
Assume the earth has an even distribution of mass, or just don’t worry about the rounding error. |
Gravitational constant is the point value, not to be confused with the small g of gravity at that point.
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...point value of the total mass.
Used for planetary interaction calcs and such. |
OK, smart Alec, give me the answer for both big G and little g.
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Ok, the G is earth-sized massive whereas the g is zero.
If we had a tunnel thru the center you can imagine that you would fall to the center, with diminishing g as the center is approached and Coriolis kicking your ass the whole way down and back the other side a ways. ;) |
Sorry, but my first thought was: "Ok, a thread started by someone who didn't pay attention in science class and missed the explanation of weight versus mass..."
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If you accept the equivalency principle of ma=F=mg, then "weight" is the total sum of forces on an object to keep it un-accelerated in the local coordinate system. That would mean that the buoyancy force is absolutely part of it, and the weight of an object within water is less than the weight of that object outside of water...in fact, a floating object has zero weight. |
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I think you ASSUmed physics was the only way to weigh in on this question. ;) |
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Really? What other branch of science might deal with this question?
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How about Ocean science?
I've done some design work for deep (miles down) submersibles. Controlling neutral buoyancy is kind of a big deal. |
Check out syntactic foams which resist this...
https://nautiluslive.org/sites/defau...?itok=U-Z8MCjc |
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Id say it only seems like things might weigh less because they fall to the bottom slowly. Both because there is still air in them and the resistence of the water
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