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Projectile motion vector problem

  1. Nov 7, 2009 #1
    1. The problem statement, all variables and given/known data
    At what compensatory angle north of east should a drone, that can only move forward at a maximum speed of 20 m/s, be launched if it is to strike a target that is 400m due east if there is a wind moving 5 m/s south?


    2. Relevant equations
    vx=20cos[tex]\Theta[/tex]
    vy=20sin[tex]\Theta[/tex]
    vf2=vi2+2ad (I think?)

    3. The attempt at a solution
    I'm not sure how to start trying to solve this, I drew a small diagram labeled with north south east and west and it shows the object's trajectory over the 400 m. I set up a chart of known and unknown variables
    x
    d=400 m
    a=0 m/s2
    t= ?
    vi=20cos[tex]\Theta[/tex]
    vf=20cos[tex]\Theta[/tex]
    vavg=20cos[tex]\Theta[/tex]

    y
    d=?
    a=9.8 m/s2
    t=?
    vi=20sin[tex]\Theta[/tex]
    vf=?
    vavg=?


    that's all I can get
     
  2. jcsd
  3. Nov 7, 2009 #2
    First define your variables. What is x and what is y? Why is acceleration in the y direction 9.8 m/s^2?
     
  4. Nov 7, 2009 #3
    x is motion on the axis from west to east and y is motion on the axis from south to north, the acceleration in the y direction is that because the only force acting on it is the gravitational force
     
  5. Nov 7, 2009 #4
    Gravity doesn't work from north to south.

    EDIT: My point is, you're approaching the problem from completely the wrong angle. It's simple vector arithmetic and trigonometry. Try re-drawing the problem with that in mind, and let us know how you do.
     
    Last edited: Nov 7, 2009
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