# Primary dimension

1. Sep 5, 2009

### jaredmt

1. The problem statement, all variables and given/known data
For each quantity listed, indicate dimensions using mass as a primary dimension and give typical SI and English units:
power
pressure
modulus of elasticity
angular velocity

2. Relevant equations

3. The attempt at a solution
im not sure i understand what it is asking for. There is another question asking the same thing but with "force" as primary dimension.
with mass being primary dimension, i guess it is referring to MLtT, but that is considered SI units isnt it? so wouldnt i just give examples of SI units? i dont see where english units come in, im confused

an example of Power in SI is 1 watt = 1 J/s. would that be the correct answer for that part? im sure this question is easy but im not clear on what they are asking for

2. Sep 6, 2009

### tiny-tim

Hi jaredmt!

I think they're asking for something like ML2/T3 (i made that up! ), watt (that's SI), and foot-pound-horsey-thingy (that's English, or imperial).

3. Sep 6, 2009

### Redbelly98

Staff Emeritus
I agree with tiny-tim. So Force would be ML/T2 in this problem, but would simply be F when force (not mass) is a primary dimension.

Don't worry about whether length L is in meters or feet, that isn't relevant here.

4. Sep 6, 2009

### nvn

I agree with Redbelly98, except T should be lowercase t.

5. Sep 6, 2009

### Redbelly98

Staff Emeritus
Typically in problems like this, when one is expressing time units, an uppercase T is used. Just as uppercase M and L are used for mass and length units.

A lowercase t is used to express time as a variable in equations, but that is not what is being done here.

6. Sep 6, 2009

### tiny-tim

I agree with Redbelly98

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