Question

The diameters of the main rotor and
tail rotor of a single-engine helicopter are 7.60 m and
1.02 m, respectively. The respective rotational speeds are
450 rev/min and 4 138 rev/min. Calculate the speeds of
the tips of both rotors. Compare these speeds with the
speed of sound, 343 m/s.

Answer 1

for the first one 450 rev/min=47.1rad/sec=omega
and radius=7.60/2=3.80
speed of first rotor=v=r*(omega)=3.80*47.1=179 m/s
to comapre with speed of sound divide 179 by 343=52.2%

Answer 2

thanks