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Homework Help: Kinematics Problem

  1. Sep 6, 2010 #1
    1. The problem statement, all variables and given/known data

    An autographed baseball rolls off of a 1.2 m high desk and strikes the floor 0.41 m away from the desk. The acceleration of gravity is 9.81 m/s2 . How fast was it rolling on the desk before it fell off?
    Answer in units of m/s.

    2. Relevant equations

    You might need to use
    v^2=vi^2 + 2a(x-xi)
    although I'm not really sure. :/

    3. The attempt at a solution

    I'm not sure how to solve this when you're not given the velocity :( I just need someone to explain how to do this, because there's 3 problems on my homework exactly like it but with different numbers. Thank you~
  2. jcsd
  3. Sep 6, 2010 #2


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    Staff Emeritus
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    There are more equations than just that one for kinematics problems. Find an equation that involves time, which you can solve for. Figuring out how long it takes the ball to hit the floor will be a big first step in solving this problem.

  4. Sep 15, 2010 #3
    hi ,

    first, i try to get the t from the free fall equation d=.5gt^2, given d=1.2m and g=9.81 m/sec/sec. Once i get the t, i use this on the equation v = d/t, d = 0.41m and t from the first part.
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