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Homework Help: 2D Kinematics - Projectile Motion Question

  1. Feb 4, 2012 #1
    1. The problem statement, all variables and given/known data

    A daredevil is shot out of a cannon at 33.7◦ to the horizontal with an initial speed of 25.5 m/s. A net is positioned at a horizontal distance of 43.7 m from the cannon from which the daredevil is shot.
    The acceleration of gravity is 9.81 m/s^2
    At what height above the cannon’s mouth should the net be placed in order to catch the daredevil?
    Answer in units of m

    Given: θ = 33.7; vo = 25.5 m/s; dx = 43.7m; a = 9.81m/s^2
    Find: dy

    2. Relevant equations

    vox = vo(cosθ)
    voy = vo(sinθ)

    [I'm stuck on what other equations I can use]

    3. The attempt at a solution

    I first drew a diagram with no problem.
    vox = (25.5m/s)cos33.7 = 21.1m/s @ a = 0m/s^2
    voy = (25.5m/2)sin33.7 = 14.1m/s @ a = -9.81m/s^2

    So we now know initial velocity in the x direction is 21.1m/s, and initial velocity in the y direction is 14.1m/s. I am a little confused on where to go from here.
  2. jcsd
  3. Feb 4, 2012 #2
    You know how far the shot goes in the x direction (43.7 m) and the initial x component of velocity, so you can calculate the time of flight.
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