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Homework Help: Angular Acceleration of Electric Motor

  1. Jan 18, 2010 #1
    1. The problem statement, all variables and given/known data
    An electric motor starts from rest at time t=0. Its angular velocity is: w=100t-4t3

    A) If the angle of rotation, x, of the motor is also zero when t=o, determine an expression for this angle in terms of t.
    B) Determine the angular velocity when x=2pi radians. Give your answer in r.p.m.

    2. Relevant equations



    3. The attempt at a solution
    For A) I thought you just integrate the expression given for angular velocity so i got x=50t^2-t^4.

    For B), I said that x=2pi, so 2pi=50t^2-t^4 but I am unsure how to solve this for x.

    Any help much apriciated,

    Mike
     
  2. jcsd
  3. Jan 18, 2010 #2

    rock.freak667

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    Homework Helper

    if y=t2, then your equation becomes:

    2π=50y-y2

    I think you can solve for 'y' now and then find 't'
     
  4. Jan 18, 2010 #3
    Clever!

    Thanks alot!

    Mike
     
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