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Projectile XY plane

  1. Feb 4, 2010 #1
    1. The problem statement, all variables and given/known data

    A ball is tossed from a building. The ball is given an intial velocity of 8.00 m/s at an angle of 20 degrees below the horizontal. It strikes the ground 3.00s later.
    a) how far horizontally from the base of the building does the ball strike the ground?
    b) Find the height from which the ball was thrown.
    c) How long does it take the ball to reach a point 10m below the level of launching

    2. Relevant equations
    Kinematic equations.

    3. The attempt at a solution
    I solved part a with no problem. 22.5m. However, I cant come up with the others using the kinematics or trig. I am missing something somewhere.
    The vel in the x direction is 7.5m/s and the vel in the y is 2.74 m/s.
    Thats all i got.
  2. jcsd
  3. Feb 4, 2010 #2


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    For (b) use
    h = Vx*t + 1/2*g*t^2
    For (c)
    Vxf^2 =Vxi^2 + 2*g*h'
  4. Feb 5, 2010 #3
    ok got b). How can I use that equation for c) when it is asking for time?
  5. Feb 5, 2010 #4


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    h = Vx*t + 1/2*g*t^2
    Use the above formula and put h = 10 m and solve for t.
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