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Homework Help: Kinematics Projective Motion Problem

  1. Mar 23, 2010 #1
    Projectile Motion
    1. The problem statement, all variables and given/known data
    Joe Carter hit a fly ball during spring training. It just cleared a 10m fence, Calculate the speed of the ball when it leaves his bat at ground level. Ignore friction.
    http://img155.imageshack.us/img155/7161/physics.png [Broken]

    2. Relevant equations

    3. The attempt at a solution
    v in x direction was found to equal 12.5 m/s which is the same as v in y direction since the tangent formed was a 45-45-90 degree angle triangle.
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Mar 23, 2010 #2
    You need to show your work, along with relevant equations. Also, what is the 8 m? Is that the distance from the batter to the wall, or the distance from the landing spot to the wall?
  4. Mar 23, 2010 #3
    its the distance from the fence to the landing point of the projectile
  5. Mar 23, 2010 #4
    Is the 45 degree angle given to you, or something you solved for?
  6. Mar 24, 2010 #5
    It was given to me, this is really all the information that was given
  7. Mar 24, 2010 #6
    Well it looks like your attempt at the solution is right so far. But it is recommended you show your work, so it doesn't look like you just copied the answer from somewhere.

    Also, what do you know about the velocity in the x-direction since the only acceleration is the gravitational acceleration in the y-direction.
  8. Mar 24, 2010 #7


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    Homework Helper

    When the ball reaches the ground, vx remains the same.
    vyf^2 = vyi^2 + 2*g*h.
    vyi is the same as vx, which you have found. h is given. Find vyf.
    Initial velocity v = sqrt(vyf^2 + vx^2)
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