mass v. weight
Wednesday, November 4, 2009 Mass is a measure of the amount of matter in an object, and remains constant regardless of where that object is (assuming it’s not moving very quickly indeed). Mass is often measured in grams or kilograms.
Weight is a measure of how strongly a large object, like a planet, pulls on a small object, like you. Weight is defined as the product of an object’s mass and the acceleration it experiences due to gravity. Weight is usually measured in pounds or newtons. An object’s weight varies depending on how far it is from the planet or other celestial body being considered, and how massive that planet is.
Of course, the reason that there is such widespread confusion about the difference between these concepts is that we almost always measure weights (or masses) on the Earth’s surface, where mass and weight can easily be converted by the simple expedient of multiplying by a constant. The upshot of this is that your mass is the same everywhere, but you would weigh less on the Moon than you do on Earth.
