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Wikijunior:Solar System/Uranus/Titania

132 bytes removed, 11 years ago
How much would Titania's gravity pull on me?: some bits seemed needlessly confusing for our audience, reword
Nearly half of the moon is made of frozen water. The rest is rock and a mixture of frozen gas.
 
==How much would Titania'sI gravity pullweigh on meTitania?==
 
Titania is a small world, but if you weighed 100 pounds or 100 kilograms on Earth, your weight on Titania would be 100 of the same units. If you want to find out exactly how much you would weigh on Titania, just take your weight from Earth, or the doctor's office, and multiply it by 1. Have you learned yet what happens when you multiply any number times one? It just stays the same, doesn't it?
But that's a pretty boring fact. So there must be something more to it—and there is! Maybe you have visited a science museum where one of the exhibits showed you that your weight would be different on some other planet.
 
The word ''weight'' is something that we use with several different meanings. Most of the time we use it to measure how much stuff we have. That is the meaning we use when we say that a bag of sugar has a net weighweight of two kilograms or of four pounds. That is also the meaning we use when we weigh ourselves at the doctor's office or at the gym, or when we calculate our Body Mass Index.
 
But we also sometimes use ''weight'' as a measure of howthe hard something is pressing downward becauseeffects of gravity. Gravity is what pulls us towards the center of the Earth when we are on Earth, or towards the center of Titania if we were on Titania. So, using this sense of ''weight'', we weigh more on Earth than on Titania because Earth's gravity pulls us towards the Earth's center more than Titania would.
 
The fact that these are slightly different meanings is something which even many grownups have a hard time understanding. Surprisingly, it is often teachers who have problems understanding this. Most teachers who teach younger children don't have too much trouble with this. It is usually the professors who teach science classes to older kids in college who have a hard time understanding this.
 
If you want to find out exactly how much you would weigh on Titania for this other meaning of weight, you need to use different units. You might just borrow the names of the units we normally use for this purpose, and use the same number here on earth with a new unit that we will call kilograms-force or pounds-force. If we do that, then on Earth the number of these units you weigh in this new meaning of the word ''weight'' is the same as the number of pounds and kilograms you weigh at the doctor's office. But if you go to a different planet or moon, then your weight in pounds or kilograms would stay the same, but your weight in pounds-force or kilograms-force would change. So it doesn't work so well to use the names that are so much alike, if you are not on Earth. In order to keep track of the differences more easily, you can instead use a newer unit that was invented to help keep you from getting confused about these differences.
 
That modern international unit used for this purpose is something called a newton, but that does not mean that it is some "new" kind of "ton". Actually, it was named after a man called Isaac Newton who lived in England about 300 years ago—maybe you've heard the story about the apple falling on his head, helping him to figure out how gravity works. YouYour probablymeasurement have not learned about this new unit yet. Even your parents might not know much about it, because it wasn't used so much, not even by their teachers and other grownups when they were as work, when your parents were your age. More people use thesein newtons today,describes andhow youhard willgravity useis them more often aspulling you get olderdown. On Earth, if you weigh 51 kilograms or 112 pounds, your weight in this different meaning, measured in these new units, is 500 newtons. We only use this "weight" for some special purposes, when we are really interested in how hard we push down on something because gravity is pulling us.
 
Then your weight in newtons would be less on Titania, only about one twenty-sixth of what it is on Earth. To find your weight in newtons as you stand on Titania, just take your weight from the doctor's office on Earth, and if that weight is in kilograms, multiply it by 3/8. Or if that weight is in pounds, divide it by 6 to get newtons. But then you'll have to add in the weight of your spacesuit as well, because that is pressing down on the surface just like you are.
 
That way you know that if somebody talks about their weight in newtons, it is a special meaning of the word ''weight''. YOuYou have now learned that this weight is something different from the normal meaning we use when we go shopping, or when we weigh ourselves to keep track of our health and fitness, or to be grouped into different weight classes so we compete against people our own size in many sports, such as judo, boxing, weight-lifting, and wrestling.
 
==Who is it named after?==
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