I hope u r asking for g-valu means gravity ///As we speaks about Gravitational force on a body represent the weight of the body ,so weight of the body varys according to the gravity. This is given by the expression Weight = MG. m-the mass of the body. g-the acceleration/falling/speed due to gravity. When this g gets affected then gravitational force varies.
g-value is affected by various factors. They are
1.The heights/altitudes value lesser the g. as we go highr and higher away from the centre of the planet or away from the surface of the respective ground level eg earth surface , g decreases
2.The depth/towards the focal point of gravity. As we go towards the centre of the earth or planet or gravity, apart from external pressure once again g decreases
3.if a body gets immersed in a liquid then the weight is affected by the molecular density . So the weight is reduced so the value of g also reduces.
4.Due to rotation of the earth or planet the centrifugal acceleration would decrease the value of g, the most along the equator. g could be proved to be GM/R2. G is the Newton's law of universal gravitationa G where its a constant ,M-mass of the earth ,R- radius of the earth. Hence due to non even spherical shape of the earth g value varies