# Question: 3 question 560 the thrust f of a free propeller...

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3. (Question 5.60.) The thrust F of a free propeller depends on
density r, rotation rate n (rev/sec), diameter D, and forward
velocity V. Ignore viscous effects. Tests on a 0.25m diameter
propeller, in a sea level wind tunnel, give the following data at V
= 20 m/s: (n = 4800 rpm, F = 6.1 N), (n=6000 rpm, F = 19 N),
(n=8000 rpm, F = 47 N). The relevant dimensionless quantities are
C_{f} = F/(r n^{2} D^{4}) and J =
V/(nD).

a) Plot C_{f} vs. J

b) Determine the expected thrust from a 1.6M diameter propeller
at 3800 rpm flying at 225 mi/hr at 4000m altitude ( r = .8191
kg/m^{3}).