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Homework Help: A question and no idea what to do

  1. Sep 25, 2005 #1
    determine the inital velocity of a projectile that is luncked horizantaly and falls 1.5m while moving 16m horizantaly
    i tried everything all i figerd out is that they r displacmednts the accelaration is 9.8 and nothing i dont have enogh info to do anything
    plz help me
     
  2. jcsd
  3. Sep 25, 2005 #2

    Päällikkö

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    Divide the motion into x and y components and deal with them as if you were dealing with one-dimensional motion.
     
  4. Sep 25, 2005 #3
    can u plz elaborate
     
  5. Sep 25, 2005 #4
    and any way that dosnt work becuse i have no angles to detrime wat the x and y componants are
     
  6. Sep 25, 2005 #5
    that would only work if these were vectors not displacment
     
  7. Sep 25, 2005 #6

    Päällikkö

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    Well...
    [tex]x = v_0t[/tex]
    [tex]0 = y_0 -\frac{1}{2}gt^2[/tex]
    Does that help at all?
     
  8. Sep 25, 2005 #7
    yeah it helped i acctualy figerd the question thx sooo much
     
  9. Sep 25, 2005 #8
    now can u plz look at my other thread and plz ohh plz help with question 1 b,c and q 2
     
  10. Sep 25, 2005 #9

    Päällikkö

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    Glad to hear that :).

    Did you understand where the equations I gave came from?
     
  11. Sep 25, 2005 #10
    ummm well yeah for one of them
     
  12. Sep 25, 2005 #11
    u assumed viy is 0 and took it our of the equation right
     
  13. Sep 25, 2005 #12

    Päällikkö

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    The full equations:
    [tex]x = x_0 + v_{x0}t + \frac{1}{2}a_xt^2[/tex]
    [tex]y = y_0 + v_{y0}t + \frac{1}{2}a_yt^2[/tex]
    Let [itex]x_0 = 0[/itex]. As the projectile's fired horizontally: [itex]v_{y0} = 0[/itex] thus [itex]v_{x0} = v_0[/itex]. No force affects the projectile in x-direction, so: [itex]a_x = 0[/itex]. In y-direction: [itex]a_y = -g[/itex] (- as it's downward). The final altitude of the projectile is [itex]y = 0[/itex].

    Hence
    [tex]x = v_0t[/tex]
    [tex]0 = y_0 -\frac{1}{2}gt^2[/tex]
     
  14. Sep 25, 2005 #13
    i was woundring if u could help me with the other thread plz help me i really need it i have a test i need to pass
     
  15. Sep 25, 2005 #14
    thx for the explination
     
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