Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Using quadratic interpolation in matlab how ?

  1. Apr 17, 2008 #1
    http://img337.imageshack.us/img337/8922/problemcmi0.jpg [Broken]

    Can anyone explain to me please how this problem is solved ?
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Apr 17, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Two ways, take your pick.

    Set v(t) = 35, then use the quadratic formula. OR

    set t = each of the possible answers, which is closest to 35?
  4. Apr 17, 2008 #3
    Well this is basically what i have done But im not sure why im getting to positive values for t ?
    I would like to :
    Please feel free to tell me if the quadratic equation i used is wrong:-

    a=8.66; b=-349.67;c=3523.18;
    qf=[qf1 qf2]

    I got qf=

    21.0571 19.3025

    Is the function in matlab defined as:
    Ax^2 +bx + c


    Ax^2 -bx +c
    Last edited: Apr 17, 2008
  5. Apr 17, 2008 #4
    Anyone please ? I have to submit this in 2 days please help...
  6. Apr 17, 2008 #5
    Found it finally :

    http://img507.imageshack.us/img507/2144/partcns7.jpg [Broken]

    This line basically i dont understand:-


    Why minus ? I ued trial and error so i dont really know how i got it. May anyone explain please ?
    Last edited by a moderator: May 3, 2017
  7. Apr 17, 2008 #6
    In addition to what i posted:

    Ok now i can see i figured out the answer But what does not makes sense to me is that the velocity 35m/s is obtained twice between 18 & 22 seconds , 22 & 24 seconds. ! So theoretically i should be having 2 answers. Is there a Physical meaning of why im having one answer ?
  8. Apr 19, 2008 #7
    Anyone please help me submission is tommrow
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook