Mass versus Weight: The terms mass and weight are commonly interchanged, however an objects mass does not change from one environment to the next, whereas weight can. Mass is the amount of matter in an object and it is also described as a measure of an objects inertia. Inertia can be thought of as how hard it is to stop an object, when in motion, or get it to move, when not in motion. The mass of an object never changes, unless you add mass to it or take mass away.
If you took a 300lb barbell to the moon it would have a mass of 300lbm or 136 kg, the same as on Earth. However, on Earth the barbell would weigh more than it would on the moon (approximately 6 times more). Weight can more accurately be described as a force due to gravity and from Newton's laws we have the relationship F=ma. This allows weight to change in different gravitational fields because while the mass (m) stays constant the acceleration (a) due to gravity can change.
This page created 26 Feb 2012 03:45
Last updated 01 Mar 2016 19:59