This is a very good question, and can actually be a little confusing, for someone new to physics. I will do my best to explain it to you, however. "Weight" and "mass' are two completely different things, altogether, although they are related, both mathematically and otherwise. However, the best place to start is to first talk about what "matter" is. "Matter" is anything that has takes up space (has volume) and has mass, like a rock. You can touch matter, paint it, or divide it up into little pieces; it is, to use a very untechnical term, just "stuff." The amount of matter in an object is called its "mass." This can be deceiving, though, because a very large piece of matter might really have very little matter in it, and so would have very little mass; think of a big piece of styrofoam or a large pumice rock (those light rocks, from volcanoes, that can float in water); they would be big, but would have little mass. On the other hand, you might have a very small piece of gold, say the size of your fist, but it would have a lot of large, closely-packed atoms, and so would have a lot of mass, even though it has a very small volume. So mass doesn't always really have to do with size, as some big things can have little mass, while some small things can have a lot of mass. Mass, like most things in physics, can be measured, of course, and when it is, the amount of an object's mass is stated in units called "kilograms." Okay, so now let's talk about what "weight" is, and then after that, we will compare and contrast the two, and at that point, I think that they will make sense to you. Be patient with me, here, and don't give up, until you have read it all, okay? "Weight" is a force, caused by gravity. And, as you know, a force is just a push or a pull on an object. Out in space, far from the surface of the earth, there is very little gravity, so there is very little pull (gravity) from the earth; that means our fistful of gold would now have no weight. So, if you were to put the fistful of gold onto a bathroom scale out in space, like in the space shuttle, there would be no force pulling the gold down onto the scale, and the gold would have no weight, right? But be careful, here, because the gold still is made of those same large, closely-spaced gold atoms, and so it still has the same amount of mass; it still has matter, or, "stuff." Mass, yes, but not weight...got it? If I were out there in the space shuttle with you and the gold, and if I asked you to take your shoe and sock off, then kick the piece of gold with your bare foot, how would that feel? The gold has no weight, so would it be easy to kick? Answer: No, it would still have the same amount of matter, the same amount of mass, and so it would still have the same amount of inertia, which is the resistance that matter offers to any change in its motion. So, if you were to kick it with your bare foot, even though you were in space, you would break your toes and it would be really painful. Now imagine that you pick up the bathroom scale, hold it in your hand, and push against the fistful of gold that is floating in the air, in front of you. As you push, you would notice that the bathroom scale would show a reading, because it takes a force to make the mass of gold overcome its inertia, and move. If a major league pitcher were to throw the piece of gold at you, in space, at 95 miles per hour, it would be very dangerous, because it would have a lot of force, even though its mass (amount of matter in it) was the same and even though it would have absolutely no weight out there. Does that make sense to you? If not, then consider this: If you are in space, does your body have the same amount of stuff in it? Answer: yes, of course, because you haven't gotten fatter or skinnier, just because you went into space. So, is your mass the same? Answer: yes, because "mass" is the amount of matter/"stuff" in an object (the object, in this case, is your body). But what about your weight? Answer: We already answered that one. You don't have any weight in space, because there is so little gravity out there. So here's a big "take-home" message (tattoo it on your forehead): The mass of an object does not depend on the object's location, but its weight does depend upon where it is, because there might be more or less gravity in different locations. Weight changes, but mass doesn't. Got it? Okay, here's a final way to look at it. Mass, as we stated, is measured in units called "kilograms," (kg), but weight is measured in entirely different units, called "newtons," (N). So, let's say that your body has 18 kg of mass, and you are standing on the beach, on a bathroom scale. The earth will be pulling down on your 18 kg of matter/body/stuff, causing you to now have a weight (a downward force) of 176.4 N. All of a sudden, Superman comes down and scoops you up, taking you out into space (and for a moment, we'll just forget about the lack of air,
2016-03-17 06:14:40
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answer #8
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answered by Anonymous
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