It's defined to be 0 at infinite distance, and then increasingly negative as you get closer to the center of the source of gravity. By assigning GPE (gravitational potential energy) to be negative, then the total energy of an object can be considered the sum of a postive kinetic energy and a negative potential energy and this total remains constant (absent of drag or other factors). However, you can arbitrarily choose to assign the zero point for GPE to be any point you want.
From the center of the earth to the surface of the earth, assuming the earth was a uniform solid sphere, the formula for GPE for a point at distance h from the center of the earth is
GPE = - G M (3 r^2 − h^2) / (2 r^3)
where r is radius of the earth, and G is the gravitational constant G= (6.674 x 10^(-11) m^3) / (kg s^2)
when h == r then GPE = - G M / r = - G M / h
Once you've reached the surface then the formula for a point switches to:
GPE = -G M / h.
Note that G actually varies a bit depending on the speed of the object invovled compared to the speed of the rest of the objects in the universe (the relativistic effect of high speed increasing the effective mass of an object).
Erm, no such thing was taught to me in my 12 years of schooling. If you don't elect to take physics as a subject you only get very minimal training in physics concepts - partly in general science and partly in higher math (if you even take higher maths as a subject). 99% of my knowledge of physics was learned independently from my schooling by reading books, and most of that after I'd turned 30. I can say for a fact that prior to high school, I'd never been shown any proper physics theroy at all.
It's not really fair to assume that everyone is learning the same stuff.
Were you educated in the UK though? Presumably it's different in different countries, but S14 is British, was (as far as I'm aware) school in England, and hence science is compulsory until A-Level (i.e. when you're 16). mhg and 0.5mv^2 were certainly taught at age 12 when I was at school (a few years back now, as I'm 27), and I can't see any reason why they wouldn't still be, other than exams, and hence classroom lessons, getting easier.
one effect of this variation of gravity force with distance is spaguetization as you fall into a black hole, your feet are atracted stronger than your head so you spaguetize
anyway in my example potential energy is spent though the cog is raised (thanks for teaching me that), but this points gravity as a force that in certain cases will expand the universe
talking of physics here theres a problem in which the universe goes from 0 momentum to acquire certain angular momentum(independently of the energy spent to do this this is regarded as imposible)
so why to build the lhc to test wrong concepts when conservation of momentum appears to be wrong with this example, its normal the universe is unbalanced, that drawing proves it
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if i posted this on a physics forums id get banned, again, for posting theories that disagree with accepted science
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what the hell ill post it and take the chance, i already got permabanned on the main internet physics forums but i have the right to spread my ideas dont i?
maybe those with french heritage
im not sure if anyone has ever managed to figure out what the french are so smug about... being french certainly cant be it