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Homework Help: Projectile motion firehose question

  1. Sep 24, 2011 #1
    1. The problem statement, all variables and given/known data

    In fighting forest fires, airplanes work in support of ground crews by dropping water on the fires. A pilot is practicing by dropping a canister of red dye, hoping to hit a target on the ground below.

    if the plane is flying in a horizontal path at an altitude of 86.0 m above the ground and with a speed of 69.0 m/s, at what horizontal distance from the target should the pilot release the canister? Ignore air resistance.

    2. Relevant equations

    Any constant acceleration equation.



    3. The attempt at a solution

    ax=0
    ay=-9.80

    Xo= 0
    Yo=86.0

    Voy=0
    Vox= 69.0

    Vx=69.0
    Vy=

    y=0
    x=

    I first found Ttotal by using the equation 0-86.0=0+.5(-9.80)(t^2).

    t = 4.189 seconds.

    then I found Vy.

    Vy= 0+(-9.8)(4.189)

    Vy= -41.052

    Then I realized finding Vy was a complete waste of time. ¯\_(ツ)_/¯

    Then I tried to find x.

    x-0 = (69.0)(4.189)+.5(-9.8)(4.189)^2

    x = 203.05 m/s?

    Does this look right?
     
    Last edited: Sep 24, 2011
  2. jcsd
  3. Sep 24, 2011 #2
    You are right down to where you found T total. In your last equation where you are calculating the value for x, you use an acceleration of -9.8. What is the acceleration along the x axis?(hint, you answered this when you state your value for ax.)
     
  4. Sep 24, 2011 #3
    Oh, thanks for the catch, I really appreciate it!
     
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