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Tangential and Radial Acceleration

  1. Oct 9, 2008 #1
    1. The problem statement, all variables and given/known data
    A car at the Indianapolis 500 accelerates uniformly from the pit area, going from rest to 250 km/h in a semicircular arc with a radius of 230 m.

    Determine the tangential and radial acceleration of the car when it is halfway through the turn, assuming constant tangential acceleration.

    v1=0 m/s
    v2= 250km/h --> 69.44m/s

    2. Relevant equations

    a=r [tex]\alpha[/tex]


    3. The attempt at a solution

    w1= [tex]\frac{v1}{r}[/tex]=0


    (.302)2= 02 + 2 ([tex]\pi[/tex]/2) [tex]\alpha[/tex]

    [tex]\alpha[/tex] = .02903 radan/s2

    I got this for my TANGENT: (230m)(.02903radan/s2) = 6.68m/s2

    and this is my RADIAL:[tex]\alpha[/tex] = 0.0290m/s2

    I'm not sure if I did the problem right. My answers seem wrong. Please help me =]
  2. jcsd
  3. Oct 10, 2008 #2


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    Homework Helper

    Hi kblue!1,

    The speed of .302rad/s corresponds to when the car has moved through the semicircular path, so I don't think the angle is pi/2 here.

    The alpha value is the angular acceleration; the radial acceleration that the question asks for is related to the radius and the angular velocity. What formula does it have?
  4. Oct 10, 2008 #3
    Thanks for replying alphysicist :)

    the formula for radial acceleration is V^2/r

    Is it just pi?
  5. Oct 10, 2008 #4


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    Homework Helper

    Yes, it would be pi (since the speed of 0.302 rad/s is after the car has moved through an angle of pi).

    The radial acceleration is v^2/r like you have; this is also equivalent to

    a_r=r\ \omega^2
    so you can find either v or [itex]\omega[/itex] at the halfway mark, whichever you prefer.
  6. Oct 10, 2008 #5
    Thank you for your help!
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