1) Fundamental units of
are ![[\frac{mol}{m\cdot s^2}]](https://tex.z-dn.net/?f=%5B%5Cfrac%7Bmol%7D%7Bm%5Ccdot%20s%5E2%7D%5D)
2) Fundamental units of
are ![[\frac{mol}{m^3}]](https://tex.z-dn.net/?f=%5B%5Cfrac%7Bmol%7D%7Bm%5E3%7D%5D)
Explanation:
The equation for the variable
is
![\rho =\frac{2\gamma \Phi+\Psi}{rg}](https://tex.z-dn.net/?f=%5Crho%20%3D%5Cfrac%7B2%5Cgamma%20%5CPhi%2B%5CPsi%7D%7Brg%7D)
where we have:
measured in ![[\frac{mol}{ft^3}]](https://tex.z-dn.net/?f=%5B%5Cfrac%7Bmol%7D%7Bft%5E3%7D%5D)
measured in ![[\frac{J}{kg}]](https://tex.z-dn.net/?f=%5B%5Cfrac%7BJ%7D%7Bkg%7D%5D)
measured in ![[in]](https://tex.z-dn.net/?f=%5Bin%5D)
measured in ![[\frac{m}{s^2}]](https://tex.z-dn.net/?f=%5B%5Cfrac%7Bm%7D%7Bs%5E2%7D%5D)
We can re-write the equation as
![\rho rg = 2\gamma \Phi + \Psi](https://tex.z-dn.net/?f=%5Crho%20rg%20%3D%202%5Cgamma%20%5CPhi%20%2B%20%5CPsi)
And we notice that the units of the term on the left must be equal to the units of the term on the right.
This means that:
1) First of all,
must have the same units of
. So,
![[\rho r g]=[\frac{mol}{ft^3}][in][\frac{m}{s^2}]](https://tex.z-dn.net/?f=%5B%5Crho%20r%20g%5D%3D%5B%5Cfrac%7Bmol%7D%7Bft%5E3%7D%5D%5Bin%5D%5B%5Cfrac%7Bm%7D%7Bs%5E2%7D%5D)
However, both ft (feet) and in (inches) are not fundamental dimensions: this means that they can be expressed as meters. Therefore, the fundamental units of
are
![[\Psi]=[\frac{mol}{m^3}][m][\frac{m}{s^2}]=[\frac{mol}{m\cdot s^2}]](https://tex.z-dn.net/?f=%5B%5CPsi%5D%3D%5B%5Cfrac%7Bmol%7D%7Bm%5E3%7D%5D%5Bm%5D%5B%5Cfrac%7Bm%7D%7Bs%5E2%7D%5D%3D%5B%5Cfrac%7Bmol%7D%7Bm%5Ccdot%20s%5E2%7D%5D)
2)
The term
must have the same units of
in order to be added to it. Therefore,
![[\gamma \Phi] = [\frac{mol}{m\cdot s^2}]](https://tex.z-dn.net/?f=%5B%5Cgamma%20%5CPhi%5D%20%3D%20%5B%5Cfrac%7Bmol%7D%7Bm%5Ccdot%20s%5E2%7D%5D)
We also know that the units of
are
, therefore
![[\frac{J}{kg}][\Phi]= [\frac{mol}{m\cdot s^2}]](https://tex.z-dn.net/?f=%5B%5Cfrac%7BJ%7D%7Bkg%7D%5D%5B%5CPhi%5D%3D%20%5B%5Cfrac%7Bmol%7D%7Bm%5Ccdot%20s%5E2%7D%5D)
And so, the fundamental units of
are
![[\Phi]= [\frac{mol\cdot kg}{J\cdot m\cdot s^2}]](https://tex.z-dn.net/?f=%5B%5CPhi%5D%3D%20%5B%5Cfrac%7Bmol%5Ccdot%20kg%7D%7BJ%5Ccdot%20m%5Ccdot%20s%5E2%7D%5D)
However, the Joules can be written as
![[J]=[kg][\frac{m^2}{s^2}]](https://tex.z-dn.net/?f=%5BJ%5D%3D%5Bkg%5D%5B%5Cfrac%7Bm%5E2%7D%7Bs%5E2%7D%5D)
Therefore
![[\Phi]= [\frac{mol\cdot kg}{(kg \frac{m^2}{s^2})\cdot m\cdot s^2}]=[\Phi]= [\frac{mol}{m^3}]](https://tex.z-dn.net/?f=%5B%5CPhi%5D%3D%20%5B%5Cfrac%7Bmol%5Ccdot%20kg%7D%7B%28kg%20%5Cfrac%7Bm%5E2%7D%7Bs%5E2%7D%29%5Ccdot%20m%5Ccdot%20s%5E2%7D%5D%3D%5B%5CPhi%5D%3D%20%5B%5Cfrac%7Bmol%7D%7Bm%5E3%7D%5D)
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