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Homework Help: Solving 2D projectile motion problem for angle, given displacement and time.

  1. Oct 1, 2011 #1
    - I need to find the appropriate launch angle that will land an object 65 meters north of my position. Therefore Δdx = 65m [N]
    - I am told that the time the object take to hit the ground is 5.23 seconds. Therefore Δt = 5.23s
    - I then used the equation Δdx = v1xΔt to find v1x = 12.43 m/s.

    After this I haven't a clue what to do next. Would someone kindly outline the steps I need to take to find the launch angle. Muchas gracias:smile:.
  2. jcsd
  3. Oct 2, 2011 #2
    If you look at the projectile motion in the y (up) direction [tex] y = y_0 + v_{yo}t + \frac{1}{2}a t^2 [/tex] the only variable you don't know is the initial velocity in the y direction [itex] v_{yo} [/itex]. Can you express [itex] v_{yo} [/itex] in terms of the launch angle and v1x? In this case the equation can be solved for the launch angle.
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