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Need The sum of time to calculate speed

  1. Jun 8, 2004 #1
    To all
    Don't you need The sum of time to calculate speed.
    This is the question in my book

    A horizontal force of 280 N is exerted on a 2.0 kg discus as it rotated uniformly in a horizontal circle (at arms length) of radius 1.00 m. Calculate the speed of the discus.

    I am not he smartest person around but I just for the life of me can not figure how to get the time. am I suppost to assume it.

    Last edited by a moderator: Mar 7, 2013
  2. jcsd
  3. Jun 8, 2004 #2


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    Science Advisor
    Homework Helper

    As far as I can tell, the discus is undergoing uniform circular motion.

    [tex]F_{net} = F_{centripetal} = \frac{Mv^2}{R}[/tex]

    You know all the values except v for which you need to solve.
  4. Jun 8, 2004 #3

    The same formula is in the book but worded diff
    That helped alot
    This is my first physics class of many and I can now see it will be along road.
    I am taking the class on line and I can see I needed a real class.
    Thanks again
  5. Jun 8, 2004 #4


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    Yes, physics unlike many other classes will be quite difficult without some guidance to help you "unwire" a lifetime of mostly false intuitions about the workings of the natural world. The only advice I have is to stick with it and you will make it through with a good understanding. I never thought of my self as particularly intelligent either, but through hard work, and really thinking through the implications of the physical laws and methods i've learned, I have succeeded and made it through all my classes with A's. My advice to you for success would be the same.
  6. Jun 9, 2004 #5


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    Staff: Mentor

    Don't sweat it, it appears to me to be a poorly worded problem. I also would have guessed the force was a torqure accelerating the disk, not the centripedal force on it.
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