What do you call the effect of gravity on a kilogram weight?

The kilogram is the fundamental SI unit of mass. In Newtonian physics, the mass of an object is the same no matter where it is in the universe -- on Earth, the Moon, Jupiter, or floating around the vast void of space -- or how fast it is moving. Weight, on the other hand, is a function of an object's mass and the magnitude of the acceleration of gravity (which is also a function of mass). In other words, an object's weight varies depending upon where it is. A one-kilogram mass will have a greater weight on Earth than on the moon and a greater weight, still, on the surface of Jupiter than on Earth. Weight is given by the formula W = mg, where m is mass and g is the acceleration due to gravity, which is 9.8 m/s2 on Earth. A one-kg mass, therefore, will have a weight of 9.8 kg-m/s2, or 9.8 newtons (N).