Using quadratic interpolation in matlab how ?

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Discussion Overview

The discussion revolves around solving a problem involving quadratic interpolation in MATLAB, specifically related to finding the time at which a velocity function equals 35 m/s. Participants explore different methods for solving the quadratic equation and express uncertainties regarding their calculations and interpretations.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant requests clarification on how to solve a problem involving quadratic interpolation.
  • Another suggests two methods: setting v(t) = 35 and using the quadratic formula, or testing each possible answer to find the closest to 35.
  • A participant shares their quadratic formula calculations, expressing confusion about obtaining two positive values for time (t) and questions the correct form of the quadratic equation in MATLAB.
  • Another participant expresses urgency for help with their submission deadline approaching.
  • One participant shares a link to their work and questions the reasoning behind a specific step in their calculations involving subtracting 35 from a value.
  • A later reply notes that the velocity of 35 m/s is obtained twice in specific time intervals, questioning the physical interpretation of having two answers.

Areas of Agreement / Disagreement

Participants express uncertainty and confusion regarding the calculations and interpretations of the results. There is no consensus on the correct approach or the physical meaning of having multiple solutions.

Contextual Notes

Some participants mention specific values and calculations without confirming their correctness. There are unresolved questions about the form of the quadratic equation used in MATLAB and the implications of obtaining two solutions for time.

Who May Find This Useful

Students or individuals working on problems involving quadratic interpolation and MATLAB, particularly those seeking assistance with similar homework or conceptual challenges.

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http://img337.imageshack.us/img337/8922/problemcmi0.jpg

Can anyone explain to me please how this problem is solved ?
 
Last edited by a moderator:
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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?
 
Well this is basically what i have done But I am not sure why I am getting to positive values for t ?
I would like to :
Integral said:
Set v(t) = 35, then use the quadratic formula.

Please feel free to tell me if the quadratic equation i used is wrong:-

a=8.66; b=-349.67;c=3523.18;
discr=qrt(b^2-4*a*c)
qf1=(-b+discr)/(2*a);
qf2=(-b-discr)/(2*a);
qf=[qf1 qf2]

I got qf=

21.0571 19.3025


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

or

Ax^2 -bx +c
 
Last edited:
Anyone please ? I have to submit this in 2 days please help...
 
Found it finally :


http://img507.imageshack.us/img507/2144/partcns7.jpg

This line basically i don't understand:-

p(3)=p(3)-35

Why minus ? I ued trial and error so i don't really know how i got it. May anyone explain please ?
 
Last edited by a moderator:
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 I am having one answer ?
 
Anyone please help me submission is tommrow
 

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