1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Rotational motion

  1. Jun 29, 2010 #1
    1. The problem statement, all variables and given/known data
    The diameters of the main rotor and tail rotor of a single-engine helicopter are 7.63 m and 0.99 m, respectively. The respective rotational speeds are 459 rev/min and 4132 rev/min. Calculate the speeds of the tips of both rotors.


    2. Relevant equations
    V=Rω


    3. The attempt at a solution
    V=(3.815m)(7.65 rev/s)
    V=29.18 m/s

    V=(.495m)(68.89 rev/s)
    V=34.10 m/s
     
  2. jcsd
  3. Jun 29, 2010 #2

    collinsmark

    User Avatar
    Homework Helper
    Gold Member

    Hello mandy9008,

    Not quite. Your relevant equation is good, but your application of it is missing a little something. Here are a few clues:

    What is the circumference of a circle in relationship to its radius?

    Following the same idea, if something travels around a circle once in a given amount of time, what total distance does it traverse? And at what speed?

    Which is really the same question phrased differently, what is the relationship between the angular frequency ω (in radians/sec), and the rotational frequency f (in rotations/sec)?
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook