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Homework Help: Centripetal acceleration problem (very easy)

  1. Jul 17, 2007 #1
    A 2.5 kg object moves at a constant speed of 8.0 m/s in a 5.0 m radius circle. What is the object's acceleration?

    I'm quite sure the answer to the problem is 32 m/s^2, but apparently the right answer is 13 m/s^2. Unless I'm missing a detail about the "constant velocity" part of the problem, can some one please explain why the answer is 13.
  2. jcsd
  3. Jul 17, 2007 #2


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    Gold Member

    Welcome to PF, Coding... but you're in the wrong forum. This is pretty obviously a homework question, which is not allowed in this section. As such, you must show what you've already done by way of figuring it out.
  4. Jul 17, 2007 #3


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    [tex]a_c= \frac{v^2}{r} [/tex]

    The mass is superfluous.
  5. Jul 18, 2007 #4


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    Science Advisor

    How could you possibly have got "32 m/s^2"? The only way to combine the numbers given to get 32 would be "82 times 2.5 divided by 5". If you do that, your units would be kg m/s2, not m/s2. Since there is no mass unit in acceleration, as bel says, the mass is irrelevant.
  6. Jul 18, 2007 #5
    duh.. 32 units is the force, 13units is the acceleration
  7. Oct 14, 2009 #6
    acceleration = v*v/r
    = 8*8/5
    = 64/5=12.8
    = 13 (approx)
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