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Homework Help: How is this gravity question wrong?

  1. Oct 4, 2009 #1
    1. The problem statement, all variables and given/known data

    While trying out for the position of pitcher on your high school baseball team, you throw a fastball at 86.0 mi/h toward home plate, which is 18.4 m away. How far does the ball drop due to effects of gravity by the time it reaches home plate? (Ignore any effects due to air resistance and assume you throw the ball horizontally.)

    2. Relevant equations

    3. The attempt at a solution
    86 miles per hour = 38.44544 meters/second
    18.4 meters / 38.44544 meters.second =0.4786 seconds
    0.4786 seconds x 9.81 = 4.695 meters
  2. jcsd
  3. Oct 4, 2009 #2


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    Gold Member

    What are your units on the last equation? That should immediately tell you you are wrong.

    Use your kinematic equations for an object in freefall.

    y = y_0 + v_{0y} t + \frac{1}{2}at^2 [/tex]
  4. Oct 4, 2009 #3
    Ok I did:

    It said my answer was wrong.

    Then I did 0+0+1/2(9.81)(0.478)[tex]^2[/tex]
    Still said it was wrong.

  5. Oct 4, 2009 #4
    And it said that answer was wrong, my last available attempt :(
  6. Oct 4, 2009 #5


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    Gold Member

    1] What answer did you get? How are we suppsoed to help you if you don't tell us what you're done?

    2] Forget the numbers. How are you thinking through this problem?
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