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Homework Help: Catapult Projectile Question wow

  1. Jan 22, 2009 #1
    1. The problem statement, all variables and given/known data

    A catapult on a cliff launches a large round rock towards a ship on the ocean below. The rock leaves the catapult from a height H = 35.0 m above sea level, directed at an angle theta = 48.7° above the horizontal, and with a speed v = 26.1 m/s. Assuming that air friction can be neglected, calculate the horizontal distance D traveled by the projectile.

    2. Relevant equations
    x=x0+ Vx0t

    3. The attempt at a solution

    Ok, So I plugged in my knowns to find the time for this, using the first equation setting it up like this 4.9t^2-19.6t+35, where vy0t=26.1*sin48.7 gave me 19.6 then I plugged in my values to the Quadratic formula where the answers I got were 2.97 and 1.03 respectively to find time, so I use the lower of the two numbers and I plug it back into x=x0+Vx0t, since intial D is 0 you add 26.1*cos(48.7) to give 17.2 then you times it to the time calculated 1.03 to get 17.72 m...its not right, I don't understand where I am going wrong Ive set it up 7 different ways... This seems like a relatively easy question I only have 2 more tries left on it out of 10. Would someone point me in the right direction Im getting frustrated at this point and feel like and idiot considering its only ch.2.
  2. jcsd
  3. Jan 22, 2009 #2


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    Homework Helper

    I would recalculate your quadratic
    Only this time I would use 4.9t2 - 19.6t - 35 = 0

    You might get a better result.
  4. Jan 22, 2009 #3
    LowlyPion thank you so much you were right that simple error completely distorted everything! :)
  5. Jan 22, 2009 #4


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    Homework Helper

    I got very suspicious when I saw the solution had 2 imaginary answers.

    Glad it worked out.

    Good Luck.
  6. Jan 23, 2009 #5
    I'm gonna have to write that one down. :biggrin:
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