The_Red_Hawk wrote:
But gravity is affected by:
1. Distance from the object.
True. The gravitational
force between two objects is a function of the distance between them. F = GmM/r^2, where G is the gravitational constant, m is the mass of the object we are looking at, M is the mass of the object "
supplying"
the gravity, and r is the distance between them. Since F = ma (force = mass times acceleration, Newton's 3rd Law I think), we typically definte g = GM/r^2 as the "
gravitational acceleration"
.
2. Rate of acceleration/deceleration.
False. Gravity
is an acceleration. The force of gravity on an object is that object's mass multiplied by the gravitational acceleration on it. If there are other forces acting on the object, then the total acceleration will not be just due to gravity. But the gravitational force itself is not affected.
I suppose you might be able to make some argument about an object exerting a gravitational force while it is accelerating away from you...but that does not seem to be what you are saying.
3. The fluid it's immersed in.
False. An object immersed in a liquid feels the exact same force of gravity than one not immersed in the liquid. It's just that in the liquid, there are buoyant forces which act to "
slow"
the object's rate of descent. It's the same as air resistance, the force of gravity is the same, but another force is added in the opposite direction. So the total force is different, as well as the total acceleration...but gravity is unaffected.
4. The mass of the object.
Could be true or false, depending on what object you are referring to. The gravitational acceleration that the Earth imparts on us does depend on the mass of the Earth, but it doesn't depend on our mass. The force that is applied to us, though, does depend on our masses. (See the equations in #1.) This is why objects fall at the exact same speed no matter how much their mass is (since their acceleration is exactly the same, that due to gravity), but if they were to hit something the more massive object would do much more damage (since the force the object would exert would depend on the mass of the object).
Game on,
____________________________
"
He who is certain he knows the ending of things when he is only beginning them is either extremely wise or extremely foolish; no matter which is true, he is certainly an
unhappy man, for he has put a knife in the heart of wonder."
-- Tad Williams