# Imparcticle needs HELP

1. Sep 9, 2004

### Imparcticle

Class started as usual on Tuesday, as my conceptual physics teacher started us on notes on scientific notation. I'm usually good with numbers and having had experience in scientific notation, it was no big deal--at first. Later into our notes, my teacher started doing conversions using sci.not. I still understood it, but not the class. I may have been the only one who got it, and if not one of few in that particular class. Unfortunately, my teacher came back the following day with a whole new method that was supposed to be "simple". It has confused me entirely. So, we have a quiz tomorrow and I don't understand the subject...not a good mix.

Okay, initially he did the problems for conversion by using conversion factors. For example, he would convert mm to nm and then convert to scinot. I totally understood that. BUT, he moved on to conversions involving things like: 10cm2= km2. I figured out how you would do this kind of problem; just do the conversion as though there were no ^2s and after the conversion multiply the exponent by ^2. But apparently I was mistaken because my teacher started working out the problem in a way which I did not understand and eventually stopped and said he would go and figure out a simpler way.

The simpler way is indeed simple: you just use a chart with labled conversion units. So if you are converting m to dm, you count the place values from m to dm and use that for some sort of decimal operation. I don't quite get it.

here are some conversion problems from my hmwk for example:

10.0 cm2= ___________m2

1.45 x 10[su]9[/sup] = ___________ Gm (I really need help with this one)

thanks

2. Sep 9, 2004

### robphy

Here are some hints.
Since 1 cm=10-2 m,
5 cm3= 5 (10-2 m)3 = 5 (10-2)3 m3 = 5 (10-6) m3.

3. Sep 9, 2004

### Imparcticle

10 cm2____________m2

1cm=10-2m
1.00 * 10-4

is that right?

if so, can you help me with the second problem I posted?

thanks

4. Sep 9, 2004

### recon

If I am not mistaken, 1 cm2 = 10-4m2

So, 10 cm2 = 10 x 10-4m2 = 10-3m2.

I don't think your second question was clear. Was it 1.45 x 109cm or 1.45 x 109m or something else?

5. Sep 13, 2004

### Imparcticle

How do you get -3 as an exponent?

6. Sep 13, 2004

### Math Is Hard

Staff Emeritus
101 * 10-4= 10-3

or more generally

am * an= a(m+n)

Last edited: Sep 13, 2004