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Kinematic equations

  1. May 16, 2008 #1
    When doing SUVAT problems, why does the item which begins motion later given a time "t-x" where x>0. For example, if dropping a ball, and then dropping another ball 5 seconds later, the first ball's time can be expressed as "t" and the second ball's time as "t-5". Why is it not t+5?

  2. jcsd
  3. May 16, 2008 #2


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    Hi nokia8650! :smile:

    Because the SUVAT formula you're using (I assume) only works if the ball is stationary at t = 0.

    Imagine each ball has its own clock, the first showing t1 and the second showing t2.

    So t1 = 0 when the first ball starts.

    And t2 = 0 when the second ball starts, which of course is when t1 = 5.

    So t2 = t1 - 5. :smile:
  4. May 16, 2008 #3
    Thanks alot!
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