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Homework Help: Firefighter hose physics problem

  1. Oct 13, 2004 #1
    Help:(

    1) A firefighter, 50m away froma building, directs a hose at an angle of 30*, if the initial speed of the stream is 40m/s, what height does it hit the building?

    i'm guessing i make a triangle and solve for h

    tan30= h/50, solve for h, i get 28 m

    .....but it's not the right answer, what am i doing wrong?

    2) A rifle is aimed horizontally at the center of a large target 200m away. The initial speed of the bullet is 500m/s. A) Where does the bullet strike the target? B) What angle above the line of sight should the rifle be to hit the target?

    I don't know what equation to use:(
     
  2. jcsd
  3. Oct 13, 2004 #2

    arildno

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    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    1) Why do you think the water will flow as a STRAIGHT line??
    It does not; it follows the parabola given by ordinary projectile motion
    2)Similarly here
    3)Don't double post
     
  4. Oct 13, 2004 #3
    ugh, should have been obvious:(

    so i would have to find t, using the equation X=Xxo+Voxt+1/2axt*2

    50=40t + 4.9t^2

    solve for t using the quadratic equation

    then plug in t into Y=Yyo+ Voyt+1/2ayt^2

    Yyo= o
    Voy=20
    a= 9.81
     
    Last edited: Oct 13, 2004
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