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Homework Help: Kinematics Problem

  1. Sep 12, 2008 #1
    1. The problem statement, all variables and given/known data
    Directly from my homework.

    One of the fastest recorded pitches in major-league baseball, thrown by Nolan Ryan in 1974, was clocked at 100.8 mi/hr. If a pitch were thrown horizontally with this velocity, how far would the ball fall vertically by the time it reached 61.2 ft away?

    It wants the answer in ft.

    2. Relevant equations
    LaTeX Code: x = x_0 + v_0 t + (1/2) a t^2

    3. The attempt at a solution

    I started by converting mi/hr to ft/s and got 147.84 ft/s. So with this I figured that the ball would travel the 61.2 ft in 0.41396 seconds. From there I plugged it into the relevant equation to get y = 0 + (0)(0.41396) + (1/2) (-9.8) (0.41396)^2 to get an answer of -0.8934 ft.

    The problem is that my question comes with an answer range that says my answer should fall somewhere between 1.8 and 3.6 ft. I've checked and double-checked the problem and I thought I've done it right, but I wanted to get a second opinion. Did I do the problem correctly and the answer range is just wrong, or am I missing something?
  2. jcsd
  3. Sep 12, 2008 #2


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    Homework Helper

    Welcome to PF.

    Shouldn't you be using a different value for gravity in ft/s2
  4. Sep 12, 2008 #3
    And there's the small detail I overlooked. Its always something simple. Thanks! And thanks for the welcome. Just started my physics class this semester, so sometimes the little things like that escape me.
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