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Calculate the density at which the available thrust is equal to the minimum drag

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Oct31-12, 05:23 PM
P: 20
Calculate the density at which the available thrust of a jet propelled aeroplane is equal to the minimum drag for the full fuel load case. Use the simplest assumption for the variation of engine thrust with density.

Wing area, S = 29.5
Weight, W = 88000
CD,0 = 0.02
k = 0.044
Max thrust (at sea level) = 16000N
CT = 1.7*10^-4

I use the formula Dmin = 2((CD,0*k)^0.5)*W = 5221N

The problem I have is that I can't work out the density without the velocity but there is no way to relate velocity to drag without density. Where do I go from here?
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Nov1-12, 07:44 PM
HW Helper
P: 5,166
If you care to revise your posting, supplying the units and explaining what each of the three co-efficients is, I'll take a look at your problem.

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