Fig 3Gravity and weightevery mass pulls every otherW = m·g
Every mass attracts every other with F = G·m₁·m₂/r². G is tiny, so you only notice it when one of the masses is a planet. At Earth's surface all of that works out to an acceleration of g = 9.81 m/s². So an object's weight, the force gravity puts on it, is just W = m·g: a 1 kg mass weighs 9.81 N. Mass is how much stuff there is, and weight is how hard gravity pulls on it. On the Moon your mass is the same but your weight is about a sixth.