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!

Differential equations (swinging door)

  1. Feb 15, 2017 #1
    1. The problem statement, all variables and given/known data

    There is a swing door with a damper. The characteristic polynomial (I have done it correctly) is:
    0.5*r^2+1.5*r+0.625

    General solution for x(0)=x_0 and v(0)=v_0 is (I have found it without a problem):

    (1.25*x_0+v_0/2)*e^(-0.5*t)+((v_0+0.5*x_0)/(-2))*e^(-2.5*t)

    Now the hell begins:
    for x(0)=0.25
    What can you say about the initial velocity of the door if, once the door is let go, it swings through the closed position and then swings back from the other side? (a numerical value and an appropriate inequality should be given)

    3. The attempt at a solution

    Constants c_1 and c_2 given the initial conditions (x_0=0.25).

    c_1+c_2=0.25
    v_0=(0.25-c_2)*(-0.5)-c_2*(2.5)

    The new solution:

    (0.25-(v_0+0.125)/(-2))*e^(-0.5*t)+((v_0+0.125)/(-2))*e^(-2.5*t)

    Well, now I am at my wits' end. I guess the velocity at the equilibrium position should be less than 0.

     
    Last edited by a moderator: Feb 15, 2017
  2. jcsd
  3. Feb 15, 2017 #2
    Hi, guys, I have solved it at last. No help necessary. Phew.
     
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: Differential equations (swinging door)
  1. Differential Equation (Replies: 12)

  2. Differential Equations (Replies: 1)

  3. Differential equations (Replies: 6)

  4. Differential Equation (Replies: 1)

  5. Differential equation (Replies: 1)

Loading...