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Find Initial Velocity given angle, distance, height launched from.

  1. Sep 18, 2009 #1
    1. A nerf gun in a vacuum is fired from .98 meters at an angle of 15degrees, going 7.86m. Find the initial velocity of the gun, then find the horizontal and vertical components of the initial velocity.

    Knowns
    g=-9.8m/s2
    yo
    =.98m
    xo=0m
    y=o ( the final height of the dart is 0)
    x=7.86m
    θ=11 degrees



    2. Relevant equations
    x=xo+vot
    y=yo+vot+.5gt2
    vox=vocosθ
    voy=vosinθ

    3. The attempt at a solution
    So first i simplified the x equation down to get time on one side to get
    (x-xo)/(vocos11)=t
    Then i plugged in the numbers to get
    {7.86/(vocos11)}=t

    Then i plugged in the parts for the y equation,
    -.98=voyt+-4.9t2
    Now what do i do? do take out a t and plug in the x equation?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Sep 18, 2009 #2
    Why not substitute in v_0* sin (theta) = v_0y. Then you have two equations and two unknowns and from that everything else is easy to find!
     
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