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Freefall Question

  1. Sep 4, 2006 #1
    The question is basically:
    You are on top of a edge that is 32.5m high and you drop 1 ball, moments later you throw a 2nd ball at the initial speed of 11 m/s. Which ball has a greater increase in speed, or is the increase the same? and prove it with a calculation.

    I started out with the x=x0 + v0t = .5at^2

    For the first ball I got the time to be 2.57 s and for the second ball i got the time to be 1.68 s.
    i proceed to try and work it out finding the velocity by using the v = v0 + at. and got -25.21 m/s^2 for the first ball and -27.53 m/s^2 for the 2nd.

    this is where i have the problem. is the increase in the speed talking about acceleration? because if it is acceleration then shouldnt both ball have the same increase in speed because gravity is working on both of them equally?
  2. jcsd
  3. Sep 4, 2006 #2


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    It sounds to me like there asking which ball has the biggest difference between there initial v and there final v.
  4. Sep 4, 2006 #3
    ahh i see. then for the first ball the change in v is 25.21 m/s^2 because the initial v was 0. But then for the 2nd ball the Vf is 27.53 m/s^2 but does the mean the Vi is 11 m/s? cause if i remeber correctly, units must be the same to be added or subtracted. or am i missing something?
  5. Sep 4, 2006 #4
    Sounds to me like they're asking how the hypotenuse of a triangle compares to the total length of its other sides.
  6. Sep 4, 2006 #5


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    Why does your Velocity have m/s^2 as units? m/s^2 is acceleration!
  7. Sep 4, 2006 #6
    i cant believe it. i wrote down gravity as 9.81 m/s not 9.81 m/s^2. sigh. everything works out fine now.
    thanks EP.
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