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Homework Help: Simple Mechanics confusing me:S

  1. Sep 25, 2005 #1
    A boy whirls a stone in a horizontal circle of radius 1.2 m and at height 1.7 m above ground level. The string breaks, and the stone flies horizontally and strikes the ground after traveling a horizontal distance of 10 m. What is the magnitude of the centripetal acceleration of the stone while in circular motion?

    Please help!
     
  2. jcsd
  3. Sep 25, 2005 #2

    Doc Al

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    Staff: Mentor

    Use the kinematics of projectile motion to find the initial speed of the stone. Then use that speed to calculate the centripetal acceleration.
     
  4. Sep 25, 2005 #3
    yes, I used V^2=u^2 + 2as , where V=0 and u is the speed to be found. But the answer comes out wrong.
     
  5. Sep 25, 2005 #4

    Doc Al

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    Staff: Mentor

    Try finding the time it takes for the object to fall. Then use that time to calculate the horizontal speed.
     
  6. Sep 25, 2005 #5
    Wicked. Got the answer right by working out the time. Thanx.
    PS. i got the firwst answer wrong because I assumed that V= o , but that was false
     
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