Really simple problem...

MarkSA

Junior Member
Joined
Sep 8, 2007
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243
I'm not familiar at all with the terminology for mass conversions...

I have a couple of problems like this:

1) The average density of whole milk is 1.034 g cm^-3. What is its density in lb gal^-1?
(That's how it is written on the sheet, with cm to the -3 power and gal to the -1 power)

2) If an oxygen molecule is moving at 4.78 x 10^4cm s^-1, what is its speed in mi hr^-1?

I believe 'g cm' is referring to grams/cm or grams per centimer.
These should be easy problems, but I don't know what they mean by putting units like centimeters to negative powers. I've never encountered that. Does anyone know?

As in the first example with the 1.034 g cm^-3, does that simply mean 1.034 x 10^-3 grams/cm?
 
MarkSA said:
I'm not familiar at all with the terminology for mass conversions...

I have a couple of problems like this:

1) The average density of whole milk is 1.034 g cm^-3. What is its density in lb gal^-1?
(That's how it is written on the sheet, with cm to the -3 power and gal to the -1 power)

2) If an oxygen molecule is moving at 4.78 x 10^4cm s^-1, what is its speed in mi hr^-1?

I believe 'g cm' is referring to grams/cm or grams per centimer.
These should be easy problems, but I don't know what they mean by putting units like centimeters to negative powers. I've never encountered that. Does anyone know?

As in the first example with the 1.034 g cm^-3, does that simply mean 1.034 x 10^-3 grams/cm?

it is same as

y * x^-3 = y * 1/x^3 = y/x^3

mile * gallon^-1 = mile * 1/gallon = mile/gallon

Just different, but legitimate, way of writing the units.
 
OK, thanks, I think I have it straight now. Not sure why I had so much trouble with this.
 
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