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Homework Help: Physics Question Speed/Time

  1. Nov 25, 2012 #1
    1. The problem statement, all variables and given/known data

    A ball player hits a home run, and the baseball just clears a wall 20.9 m high located 131.0 m from home plate. The ball is hit an an angle of 35° to the horizontal, and air resistance is negligible. Assume the ball is hit at a height of 0.9 m above the ground.
    (a) What is the initial speed?
    m/s
    (b) How much time does it take for the ball to reach the wall?
    s
    (c) Find the components of the velocity and the speed of the ball when it reaches the wall
    vy,f = m/s
    vx,f = m/s
    vf = m/s

    2. Relevant equations
    vi(intial velocity)


    3. The attempt at a solution
    I got 8.5 seconds for the time but thats apparently not right and it's prohibiting me from further progress.
     
  2. jcsd
  3. Nov 25, 2012 #2

    tiny-tim

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    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi Debate123! Welcome to PF! :wink:

    Show us your full calculations, and then we'll see what went wrong, and we'll know how to help! :smile:
     
  4. Nov 25, 2012 #3
    Dx+Vxi*t
    DX=Vx*CoS35.t
    !3!+Vxcos35.tw
    Vi+131?Cos35.tw

    20.9+-4.9t^2+sin35/Cos35+.09
    20.9=-4.9tw2+65.1385/.8191+.09
    20.9=-4.9tw^2+91.727+0.9
    20.9-92.627=tw^2
    tw=sqrt71.727
    tw=8.46(deemed wrong by my webassign)
     
  5. Nov 25, 2012 #4

    tiny-tim

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    Science Advisor
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    i think you may have entered 113 instead of 131 :wink:
     
  6. Nov 25, 2012 #5
    I still don't know to fix my problem entirely, theres 5 parts and I can't even get 1
     
  7. Nov 25, 2012 #6
    Can someone show me the time so I can finish the problem myself please?
     
  8. Nov 25, 2012 #7
    NVM figured it put by myself
    a) Initial ball speed: 41.7 m/s
    b) Time for ball to reach wall: 3.81 s
    c) x velocity-component: 34.2 m/s
    y velocity-component: -13.4 m/s
    Speed of the ball: 36.7 m/s
     
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