1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

2nd Diff eq application - Vertical stretch

  1. Aug 10, 2016 #1
    Hello guys,
    first I am sorry I didn't use the template. I deleted it by mistake and I didn't know how to create a new thread from scratch.

    so I have two cases of the same problem, on with initial conditions of pulling down and the other pushing up, I tried different signs but It didn't work. Can anyone explain to me the difference in dealing with this?
    Screen Shot 2016-08-10 at 4.54.05 PM.png Screen Shot 2016-08-10 at 4.53.55 PM.png

    thank you
     
  2. jcsd
  3. Aug 11, 2016 #2

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Hi,
    Bit difficult to help here. I take it this is a computerized teaching situation and you did well on the picture on the left (I don't see the green shading, though). And not so well on the right. Is that correct ?
    If so, I notice you use the two roots on the left, but not on the right. Could you type your work that leads you to ##2e^{-x}## ?
     
  4. Aug 11, 2016 #3

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    You can simply recover the template by starting a new thread and then cut the template from the new thread and paste it in the existing one. Then not post the new thread.

    Looked at your work (as if I have plenty of time to do so...) and found you made a very simple mistake. I don't blame you but I blame your computerized workbook for three reasons:
    1. choosing y+ as 'down' is unhealthy
    2. working in the cgs system is very unhealthy
    3. a spring that stretches 1.11 m when 2 gram weight is appended is weird
    If you write down your two equations for the initial conditions you'll see your mistake right away :smile:.
     
    Last edited: Aug 11, 2016
  5. Aug 11, 2016 #4

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Oh, and what is the independent variable ? x ? :rolleyes:

    [edit] skip my last tip in #3; you did enter -2 at first, I can assume.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: 2nd Diff eq application - Vertical stretch
  1. 2nd order diff Eq help! (Replies: 14)

  2. 2nd order diff eq. (Replies: 1)

Loading...