Does the gravity of a body vary with its motion?
By gravity, if you mean the acceleration due to gravity (which we usually take to be 9.8 m/s2), then it is a constant. g = GM/R squared where G = gravitational constant M = mass of earth (or whatever is the cause of the acceleration) R = radius of the earth (or whatever is the cause of the acceleration) If the mass moves very close to the speed of light, its mass would increase, but in the above equation, only the mass of the earth is considered, so the acceleration due to gravity would be the same.
In Newtonian mechanics, gravity is a force of attraction between two objects with masses. The force F measured in newtons (N) is given by: F = G* [Mm]/d^2 where M and M are the masses of the two objects (kg) and d is the distance in metres between the centres of gravity of the two objects. G is the universal gravitational constant and = 6.7 X 10^(-11) Nm^2kg^(-2) The constant is very small and it means that gravitational forces are negligible unless one of the masses is very large. That is why all object on the Earth feel the Earth;s gravitational attraction. Now imagine two large planetary objects moving away from each other. As they do so d^2 gets smaller and and so the gravitational attraction between the two objects gets less. Here gravitational attraction does vary as a result of motion. You can see that gravity is not a property of a single object but a fundamental force of attraction between two objects. It takes at least two objects for the gravitational force to be manifest. E
