| The universal law of
gravitation describes the relationship between the motion and earth and the satellites
around it. the moon, etc. But for objects near earth's surface, use Fg = mg.
Though these two equations for gravity look different, they still agree with each other,
under the condition that g is the non-spinning, absolute acceleration due to
gravity. This represents the "true" weight of an object due only to its
gravitational interaction with the Earth and therefore identical to: Fg = mg = Gm1m2/r2
|
| g = Gmearth/r2 |
mearth = mass of earth
= 5.97 X 1024 kg
r = distance from center of earth to object (m) |
This shows that acceleration due to gravity, g, is not a
constant (even though we assumed it was until now), it depends on the distance between the
earth and the object. In the vicinity of the planet, the acceleration due to gravity
is the same for all bodies independent of their masses. By substituting for m2
and r, we can calculate the acceleration due to gravity for any celestial body. |
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