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: Moment of Inertia and kinetic energy question

  1. Mar 1, 2012 #1
    1. The problem statement, all variables and given/known data
    The flywheel of a gasoline engine is required to give up 550 of kinetic energy while its angular speed decreases from 720 to 400 .
    What moment of inertia is required?


    2. Relevant equations
    K=(1/2)Iw^2


    3. The attempt at a solution
    K=550J
    I'm not sure how to get the w value since the velocity is changing.
    I tried:
    550=(1/2)I(320)^2
    then solving for I
    I=0.0107
    but this is not correct.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Mar 1, 2012 #2

    Doc Al

    User Avatar

    Staff: Mentor

    The right hand side is incorrect. You want Δ((1/2)Iw^2), not (1/2)I(Δw)^2.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook