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Homework Help: Centripetal Acceleration Problem

  1. Oct 23, 2005 #1
    I am having the worst time figuring out how to solve this problem:

    A student build and calibrates an acclerometer, which she uses to determine the speed of her car around a certain unbanked highway curve. The accelerometer is a plumb bob with a prtractor that she attaches to the roof of her car. A friend riding in the car with her observes that the plumb bob hangs at an angle of 15 degrees from the vertical when the car has a speed of 23m/s. What is the centripetal acceleration of the car?

    Ok, I have my force equations:

    The sum of the forces in the x=-Tcos75=-(mv^2)/r
    The sum of the forces in the y=Tsin75-mg=0
    I substituted T for mv^2/r, so mass cancels out, but I can't seem to figure out where to go from there.

    Any help would be greatly appreciated!!
  2. jcsd
  3. Oct 24, 2005 #2
    I didnt use the speed.

    resolve Tcos15 = m 9.81
    Tsin15 = ma


    9.81tan15 = a

    a = 2.628ms^-2
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