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Homework Help: 3D Projectile Motion

  1. Nov 19, 2009 #1
    1. The problem statement, all variables and given/known data

    A projectile of mass 1 kg is launched from ground level toward the east at 200 metres per second, at an angle of pi/6 to the horizontal. A northerly win applies a force of 2 newtons to the projectile. Find the location of the projectile and its speed at impact.

    2. Relevant equations

    I have to use calculus and derivatives.

    3. The attempt at a solution

    Since the mass is 1 kg, the force is equal to the acceleration (F= m a). If east is X-axis, then north is Y-axis and gravity acts in the Z-axis. So, a=(0 i , 2 j , -9.81 k).
    This is where I'm stuck. I don't know how to proceed.

    Please help. Thanks.
  2. jcsd
  3. Nov 19, 2009 #2
    Anyone? I need some help because this is due tomorrow morning.
  4. Nov 19, 2009 #3


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    no you don't

    Just like how you consider the vertical and horizontal components separately to calculate the normal flight of the object. Here you just have to then consider the x and Y components of the motion separately.
    resolve the forces into x and Y and it's pretty striaght forward.

    ps. by posting in your own question it marks it as answered and so people ignore it!
  5. Nov 19, 2009 #4
    How can I make it in terms of x and y components when I have a z component as well?
  6. Nov 19, 2009 #5


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    You do that separatly.
    Ignore the X and Y, just do the normal trajectory stuff to get the flight time

    Then use the force north to work out the curve in XY -
    edit, sorry you do need calculus for this, I misread it as a constant accelration, not a constant force

    ps. Be careful about which direction a northerly wind is!
  7. Jul 10, 2010 #6
    I came up with the following answers (rounded to 2 decimal places), can anyone verify?

    The projectile lands 3559.25 m away from its launch point at a heading of 353.28 degrees and a speed of 204.12 m/s
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