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Projectile launch at elevated height on angle

  1. Mar 20, 2012 #1
    1. The problem statement, all variables and given/known data

    a baseball player hits a home run. The ball's velocity as it leaves the bat is 45m/s at an angle of 36.9° above the horizontal. At the point of impact with the bat, the ball is 1 m above ground level, and as it clears the fence it is back down to 11 m above ground level. How far from home plate is the fence at this point?

    2. Relevant equations
    quadratic formula
    linear motion equations
    basic sin and cos
    v=d/t

    3. The attempt at a solution

    so I started with finding the Vv and the Vh velocties
    vh= 45cos6.9= 36.0
    Vv= 45sin36.9 = 27.0

    then I organized the information I had into two seperate headings
    Vv
    v1: 27 m/s
    v2:*27.4m/s
    a: -9.8m/s
    t:*5.5
    d: -1m

    and Vh
    vave: 36m/s
    t:*5.5
    d:*198m

    *I found the time using the quadratic formula and came up with 5.5 seconds
    * I calculated the total distance the ball travelled using the formula d = v×t and got 198 m
    * calulated the v2 for the Vv to be 27.4 m/s using linear motion equation
    I'm thinking i need a colum for the fence distance now, however, this part is slightly iffy.

    Vh for fence
    vave:
    t:T
    d: 198-D

    Vv for fence
    v1:
    v2:
    a:-9.8m/s
    t:T
    d: -11m

    At this point I've hit a dead end.
     
  2. jcsd
  3. Mar 20, 2012 #2
    The question states the ball is at 11m above the ground

    So displacement is 10m.
    Calculate your time again.(its not right)

    After you have time
    You will need to multiply it by v(h)*t to get d.(as you already did)

    Thats all.thats your answer

    I dont understand what (and why)you are doing in the latter part of your post.
     
  4. Mar 21, 2012 #3
    Hmm, I always manage to overcomplicate an easy question. thanks, I calculated my time to be 5.1 secs.
     
  5. Mar 21, 2012 #4
    Your answer appears correct.
     
  6. Mar 21, 2012 #5

    Always draw a diagram :-)
    That shortens the problem in so many ways.

    Your time is correct :-)
    Now all that is left is to find the distance.
     
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