International System Units

t_n_k

Joined Mar 6, 2009
5,455
If 1 bar = 100kPa where the Pascal [Pa] is the SI unit of pressure then presumably the unit for the time derivative (rate of change) of pressure is \(P_as^{-1}\)

\(1 \ P_a=1 \ kgm^{-1}s^{-2}\)

So presumably the unit of the time derivative of pressure in terms of the fundamental units is

\(kgm^{-1}s^{-3}\)
 

Georacer

Joined Nov 25, 2009
5,182
Actually, I think it is \(\frac{\partial P(bar)}{\partial t}=100k \cdot (-2) kgm^{-1}s^{-3}\)
given that the formula for the pressure is as you say.
 

t_n_k

Joined Mar 6, 2009
5,455
If the question was actually about conversion between units then perhaps more succinctly

\(1 \ Bars^{-1} \ <=> \ 100 \ kPas^{-1} \ <=> \ 10^5 \ kgm^{-1}s^{-3} \)

I doubt the OP has any real ongoing interest in this matter.
 

Georacer

Joined Nov 25, 2009
5,182
But the partial derivative of a function in respect to the time is
\(\frac{df}{dt}\)
not
\(\frac{f}{s}\)

One of us has a really brain-dead moment. By the end of the thread we 'll see who it is. (Please let it not be me!)
Now I saw the units reference. It was me who had the brain dead moment after all. Sigh...
 
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