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Angular acceleration and such

  1. May 18, 2008 #1
    As you press down on the accelerator of your car you see the tachometer climb steadily from 1200 rpm to 5500 rpm in 2.5 s.
    (a) What is the angular acceleration of the car?
    (b) What is the tangential acceleration of a point on the edge of the engine’s 3.8 cm diameter crankshaft?
    (c) How many revolutions does the engine make during this time?
    (d) If the moment of inertia of the crankshaft is 0.009 kg.m2, what is the torque generated by the engine?
    (e) What is the kinetic energy of the crankshaft at its maximum rpm? What is its angular momentum at that time?


    I like to make sure i'm grasping this:

    angular velocity intial and final (wi and wf)
    a. wi=125.66 wf=575.96
    wf=wi+at
    575.96=125.66-a2.5
    ang=180.12 rads-2

    b.ang=a/r
    ang*r=a
    180.12*.019=a
    a=3.42 ms-2

    c.theta=wit+(1/2)at^2
    theta=314.14+562.88
    theta=877.02 rad
    rev=theta/2pi
    rev=877.02/2pi
    rev=139.58

    d. torque=I*ang
    torque=.009*180.12
    torque=1.62 mN

    e. K=(1/2)Iw^2
    K=(1/2)(.009)(575.98(^2
    K=1492.78 J
     
  2. jcsd
  3. May 19, 2008 #2
    I cant spot any conceptual mistake... :)
     
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