# I Just Dont Get It

1. Sep 7, 2006

### BunnyHanyou

I Just Dont Get It!!!!!

Its my second day of physics and I have no idea whats going on -_- Its so riduculous We've started converting units and Im just completly lost I have 6 problems for homework and Im basically screwed :_[. Can someone please guide me through one or two of them? some of them are 286.6mm, 760mg, and 60.0ps please guide me through one or two :_[.

2. Sep 7, 2006

### Astronuc

Staff Emeritus
It seems like you are working with SI (MKS) units.

If so, is one supposed to convert each unit to its SI basis. For example, mm = millimeter, and the prefix 'milli' means 1/1000 th, or one-thousandth, and 1 mm = 1/1000 m = 0.001 m. The prefixes take the place of many 0's or scientific notation.

Another example, kg, which is kilogram. The prefix 'kilo' means 1000, and 1 kg = 1 kilogram = 1000 grams.

In the first example - 286.6 mm = 286.6/1000 m = 0.2866 m.

See - http://physics.nist.gov/cuu/Units/prefixes.html

and http://en.wikipedia.org/wiki/SI

and this is useful with some examples -
http://www.ebyte.it/library/educards/siunits/TablesOfSiUnitsAndPrefixes.html

a useful calculator
http://www.lenntech.com/unit-conversion-calculator/prefix.htm

Hyperphysics is a good general site -
http://hyperphysics.phy-astr.gsu.edu/hbase/units.html

Good for overchecking calculations
http://hyperphysics.phy-astr.gsu.edu/hbase/unitc.html#uc

Last edited: Sep 7, 2006
3. Sep 8, 2006

### civil_dude

One thing to remember also is the concept of 1; that anything divided by itself is 1. 1 foot/12 inches = 1. And that when you muliply 'anything' by 1 the 'anything' does not change. Then it is simply a matter of manipulating the units in the numerator or demominator.

4. Sep 8, 2006

### dmoravec

thats because you're dividing by 12 inches/ 1 foot so the feet cancel out.

5. Sep 8, 2006

### AO eye 5

Unit conversion

Here's a site on dimensional analysis. http://www.chem.tamu.edu/class/fyp/mathrev/mr-da.html" [Broken]

Good luck!

Last edited by a moderator: May 2, 2017