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Kinematics. cannonball was dropped- how far from the wall does it hit ground?

  1. Sep 26, 2008 #1
    1. The problem statement, all variables and given/known data
    King Arthur's knights fire a cannon from the top of the castle wall. The cannonball is fired at a speed of 45m/s and an angle of 32degrees . A cannonball that was accidentally dropped hits the moat below in 1.4s .

    a) How far from the castle wall does the cannonball hit the ground?

    b) What is the ball's maximum height above the ground?


    2. Relevant equations

    Unsure what to use.

    3. The attempt at a solution

    xi = ti = 0
    vi = 45 m/s
    vix = 45cos32 = 38.16
    viy = 45sin32 = 23.85
    ax = 0
    ay = -9.8 m/s
    yf = 0
    yi = 1/2 (-9.8m/s^2)(1.4s)^2 = 9.6 m

    horizontal v 45cos32 = 38.16
    initial v 45sin32 = 23.85

    time of fall 2.43 seconds

    57.86/9.8 = root of 5.9
    = 2.43 + 2.43
    = 4.86
    = 185.4576m


    max height
    1/2(9.8) x 2.43^2 = 28.93 m
     
  2. jcsd
  3. Sep 27, 2008 #2

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