the_sunshine Posted November 28, 2007 Share Posted November 28, 2007 Can anyone Please help me with this problem? I'm trying to use this formula (velocity = radius * angular velocity), but somehow it's not right Thank You. 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 4150 rev/min. Calculate the speeds of the tips of both rotors. main rotor? tail rotor? Compare these speeds with the speed of sound, 343 m/s. Link to comment Share on other sites More sharing options...
timo Posted November 28, 2007 Share Posted November 28, 2007 What are your solutions and what is wrong with them ? Link to comment Share on other sites More sharing options...
the_sunshine Posted November 28, 2007 Author Share Posted November 28, 2007 velocity = radius * angular velocity v1=3.8m*450rev/min= 1710/60 = 28.5m/s v2=0.51m*4150rev/min=2116.5/60 = 35.3m/s Comparison with the speed of sound: vmain rotor / vsound = 28.5m/s/343 m/s= 0.083 vtail rotor / vsound = 35.3m/s/343 m/s= 0.103 i really don't know what i am doing wrong... Link to comment Share on other sites More sharing options...
timo Posted November 28, 2007 Share Posted November 28, 2007 The angular velocity does not equal the frequency (the rev/min). Think of it: If something goes in a circle at 1 rev/sec, then the magnitude of the velocity equals one circumference per second, not one radius per second. Link to comment Share on other sites More sharing options...
the_sunshine Posted November 28, 2007 Author Share Posted November 28, 2007 i got it. Thank You! Link to comment Share on other sites More sharing options...
MrMongoose Posted November 28, 2007 Share Posted November 28, 2007 Disappointing. If only they went a bit faster! Link to comment Share on other sites More sharing options...
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