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Homework Help: Stuck on this problem

  1. Sep 22, 2004 #1
    A rock of mass 33 kg accidentally breaks loose from the edge of a cliff and falls straight down. The magnitude of the air resistance that opposes its downward motion is 239 N. What is the magnitude of the acceleration of the rock?

    I tried a=239*33 and I got 7.24 but that was wrong. Please help. I don't know what else to do.
  2. jcsd
  3. Sep 22, 2004 #2


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    What are the forces acting on the block?

    What does newton's 2nd law state?
  4. Sep 22, 2004 #3
    Did you draw a free body diagram of the falling rock including all forces acting upon the rock?

    Did you write out [itex]\sum \vec F=m\vec a[/itex]? I'm sure if you do the above and sum the forces you'll get the correct answer.
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