NCEES 2016 thermal & fluid prb 507
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Ramnares P.E.
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Use a few more significant figures in your lbm/ft^3 to slug/ft^3 conversion and you'll be almost identical to the answer. I used 1.939 slug/ft^3 and the resultant answer is 91.466 psi. Just a matter of sig figs.
Audi Driver P.E.
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Using the exact figures you provide in red through all the calculations, I get 91.488
I'm a little lost as to why gravity must be converted to slugs/ft^3. It seems that you do not have to mess with this with all the other formulas in the MERM. Where does the formula for this show up in the MERM?
Ramnares P.E.
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Looking at the problem I don't think the conversion is necessary. Perhaps the thread author is simply more comfortable working in those units >shrug<
Ramnares P.E.
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Enter the infamous g/gc.
Ramnares P.E.
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g/gc is a common fluids ratio used when mass and force and involved, i.e. lbm, lbf, or involving work of a fluid.
The MERM should have a discussion of this, if not, your Fluid Mechanics text will.
The MERM should have a discussion of this, if not, your Fluid Mechanics text will.
Ok, I figured it out.
If you use the the U.S. Customary version of the Bernoulli equation as shown in the MERM, it simplifies to P1=p1h1 + (p2v2^2/2g) where P=pressure and p=density.
1) Density = 62.4 * 1.03= 64.3 lb/ft^3
2) Convert knots to ft/sec to obtain 50.634 ft/sec
3) Convert 14.7 psi to psf by multiplying by 144 to obtain 2116.8 psf.
4) Plug and Chug
If you use the the U.S. Customary version of the Bernoulli equation as shown in the MERM, it simplifies to P1=p1h1 + (p2v2^2/2g) where P=pressure and p=density.
1) Density = 62.4 * 1.03= 64.3 lb/ft^3
2) Convert knots to ft/sec to obtain 50.634 ft/sec
3) Convert 14.7 psi to psf by multiplying by 144 to obtain 2116.8 psf.
4) Plug and Chug
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