Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Rotating masses

  1. Jul 9, 2011 #1
    How does the angular velocity change with increase in the mass?
    For example : if there is a shaft rotating at 1500 Rpm , then if a disc of 5 kg is fastened , does the angular velocity of the disc will be same as 1500 RPM , and what happens to the RPM if the disc mass is 50Kg.
  2. jcsd
  3. Jul 9, 2011 #2
    Momentum (angular or translational) is conserved. If the extra mass were simply attached from rest to the shaft, the mass would go from I[itex]\omega[/itex]=0 to some rotational momentum greater that zero. The spinning shaft would have to lose enough angular velocity such that the sum of the rotational momenta (those of the 5 Kg mass and of the shaft) was the same.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook