Not my own - but the difference between the two. My understanding is that mass stays constant, but weight changes depending on the effect of gravity. With a little more work, I could probably ace an answer on a test. But I still won't understand the difference! Maybe it's a perception problem. Can anyone help?

Your "earthly" weight is simply a force that the mass of your body exerts upon the ground which you stand. Recall Newton's age old equation F=ma. In this case, "a" is the strength of gravity exerted upon your mass by the Earth. For practical purposes, "a" is constant upon the surface of the the Earth (although technically it varies -- see my post to another of your questions regarding your weight on a mountain top vice sea-level). So if you could be transported about the Earth from spot to spot, your weight would basically be constant.

No matter where you are in the universe, your body mass is constant (not accounting for the bag of potato chips you eat now and then). What DOES change is the acceleration that is exerted upon your body by the bodies that surround it. So if you could be transported to Jupiter which is a body that has more mass than the Earth, and therefore a larger accelerative attraction "a", your weight would be greater than it is here on the Earth.

Good luck on your exam!

[This message was edited by Strider0 on 06-26-02 at 11:45 PM.]

Another way of looking at it is this: suppose you have a ball of lead, you know that the bigger the ball, the more material it contains. We tend to speak of the fact that it weighs more, but in addition to that it has more mass. The difference is that it has the same mass, that is the same amount of material, no matter where it is. But, it doesn't weigh the same on the moon as it does on the earth. What it weighs depends on the mass of the planet, the mass of the ball, and the distance between their centers. The ball of lead weighs less on the moon because the mass of the moon is about 1/80th the mass of the earth. But the ball doesn't weigh 1/80th of its weight on earth it weighs about 16 pounds on the moon if it weighs about 100 pounds on earth. The reason being that the distance between the centers is far less on the moon and weight depends on the inverse of the square of that distance. You might like to see what you weigh on othe planets etc. by plugging your weight in on the following:
Your weight on other planets

Mass_ the amount/quantity of substance contained in a certain object.

Weight_ the amount of gravitational force exerted on an object.

Hope this is sufficient,
Pin~Jinx