Mass

Mass (Encyclopedia of Science)

One common method of defining mass is to say that it is the quantity of matter an object possesses. For example, a small rock has a fixed, unchanging quantity of matter. If you were to take that rock to the Moon, to Mars, or to any other part of the universe, it would have the same quantity of matterhe same masss it has on Earth.

Mass is sometimes confused with weight. Weight is defined as the gravitational attraction on an object by some body, such as Earth or the Moon. The rock described above would have a greater weight on Earth than on the Moon because Earth exerts a greater gravitational attraction on bodies than does the Moon.

Mass and the second law

A more precise definition of mass can be obtained from Newton's second law of motion. According to that lawnd assuming that the object in question is free to move horizontally without frictionf a constant force is applied to an object, that object will gain speed. For example, if you hit a ball with a hammer (the constant force), the ball goes from a zero velocity (when it is at rest) to some speed as it rolls across the ground. Mathematically, the second law can be written as F = m ยท a, where F is the force used to move an object, m is the mass of the object, and a is the acceleration, or increase in speed of the object.

Newton's second law says that the amount of...

(The entire section is 514 words.)