The Metric System is No Fairy Tale...
In order to be successful in AP Physics, you really have to be able to use the metric system flawlessly. You need to be able to look at a unit like 560 Terahertz and know that you'll need to enter it into your calculator as 560 E12 Hz. For the purposes of calculating values, no one will know that you didn't enter it as the perfect scientific notation of 5.6 E14 Hz, but you have to know what tera means.
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I know that you live straddling the metric/english divide because in the US, we haven't just gone metric already, holding onto the length of a king's foot as a unit of measure and dividing things into 12ths, 8ths, 16ths and 32nds, for example. So, I beg of you, step into the metric system with me and learn to use it exclusively.
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Perhaps you'll find it useful to know that a meter is about a yard, a liter is about a quart, and a kilogram is about $80 worth of Godiva chocolate.
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The metric system uses prefixes attached to base units. Below, you'll see the seven base unit and a full list of prefixes.
These are the units for physics. A kilogram is not REALLY a base unit. The base unit is the GRAM. However, we measure everything in kilograms in physics. 1 kg = 1000 g.
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Any other unit you see is probably a derived unit. More on that toward the bottom of this page.
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In the next image, you'll see a list of the prefixes and their exponential equivalents. You need to memorize deci-nano on the small side and deka - tera on the large side.
Finally, you need to know some very basic conversion factors that allow you to move from english to metric for the purposes of determining if an answer makes any sense..
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1 kg = 2.2 lbs
1 mph = .447 m/s
1 kg = 9.81 N
1 hour = 3600 s
1 day = 86400 s
1 radian = 57.3 degrees
1 mile = 1.601 km
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You do not have to show work for making conversions after the first six weeks of class, you can simply make the conversions in your calculator. However, until then, you are expected to show how you made the conversion. You can use dimensional analysis, train-tracking or ratios, your choice.
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Finally, there are a lot of derived units in physics. For example, a newton is a unit of force. 1 N = 1 kgm/s/s. You can see from the derived units how a newton was derived. It was a mass (kg) times an acceleration (m/s/s). It's important for you to know how things like joules, watts, hertz and newtons are derived. Below is a table of derived units. I do not expect you to memorize these. I just wanted you to see what a lovely collection it is. When you are done here,, here is the quiz but it will not be open until mid-July.
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