The mass of an object is independent of gravitational field strength. Mass can be determined on an equal arm balance, by making comparisons against standard masses. At the same place in an external field, two objects with the same mass will have the same weight. Weight is the force that a gravitational field exerts on an object. The terms weight , force of gravity , and gravitational force are sometimes used synonymously.
Weight is a vector quantity.
At the surface of the Earth an object's weight acts downward, towards the centre of the Earth. Changes in altitude and latitude affect the gravitational field strength on the surface of the Earth. Changes in the composition of the Earth's crust affect the gravitational field strength. The weight of an object depends on its location with respect to one or more celestial bodies. The force of gravity involves the gravitational fields of objects acting upon one another.