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Homework Help: Projectile motion (am I on drugs?)

  1. Jan 26, 2008 #1
    [SOLVED] Projectile motion (am I on drugs?)

    1. The problem statement, all variables and given/known data
    I can't believe how much time I have spent on this.

    2. Relevant equations
    Constant acceleration

    3. The attempt at a solution
    Here is the data I am using to solve for

    From x direction:
    [tex]\Delta X=V_{0x}t\Rightarrow t=\frac{30}{V_a\cos30}[/tex]

    From y direction:
    [tex]\Delta Y=V_{oy}+.5a_yt^2[/tex]
    [tex]\Rightarrow 3= V_a\sin30*(\frac{30}{V_a\cos30})-16.1[\frac{30}{V_a\cos30}]^2[/tex]

    [tex]\Rightarrow 3=30\tan30-16.1*(\frac{40}{V_a})^2[/tex]

    Which gets me a negative under the radical!
  2. jcsd
  3. Jan 26, 2008 #2
    seriously I am about to lose it. i have been over this like ten times!
  4. Jan 26, 2008 #3
    Where's the negative under the radical? 40 and [tex]V_a[/tex] are both positive, right? ...
  5. Jan 26, 2008 #4
    How'd you get that "40" under the radical, anyway?? I get 34.64 ...
  6. Jan 26, 2008 #5
    Oh wow. I better look into that drugs thing. The solution is 36.7 but I am getting 42.2. But then again, I'm on drugs. So let me check again.

    Thanks B.
  7. Jan 26, 2008 #6
    Yeah, your right Bells (mind if I call ya Bells?). I'm cooked this semester. Thanks for the help.

  8. Jan 26, 2008 #7
    Happens to the best of us ... keep at it.
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