Question

Does each object have a different gravitational field strength despite being on Earth? If so why is 9.8m/s2 constantly used for gravitational field strength when solving equations like F=mxg

Answer 1

g= GM/R^2 which is constant if we measure it near the earth surface
gravitation field = force on object/object mass = GM/R^2

Answer 2

Don't confuse concepts. Gravitational Force or constant is a different value than gravity. Gravity is always 9.81m/ss and applies to any object near the surface of Earth. F=ma ( mass x acceleration). Fn ( Normal Force ) is equal to the W= mg. Fn= mg. ( the force of W and the Fn are opposite to each other, they are in equilibrium therefore they have the same value. ).