Results 1 to 5 of 5

Math Help - diff eqn question

  1. #1
    Newbie
    Joined
    Mar 2008
    Posts
    15

    diff eqn question

    Can anyone give me a 'walk through talk through' of the following problem?

    Use the Laplace Transform method to obtain the forced response of the system

    y'+2y=v(t)
    assuming zero initial conditions and t>=0 for the following cases:

    a) v(t)=t

    b) v(t)=t^2

    c) v(T)=te^-t

    Fingers crossed someone can help. I've been wrestling with it for a couple of days now.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by boab View Post
    Can anyone give me a 'walk through talk through' of the following problem?

    Use the Laplace Transform method to obtain the forced response of the system

    y'+2y=v(t)
    assuming zero initial conditions and t>=0 for the following cases:

    a) v(t)=t

    b) v(t)=t^2

    c) v(T)=te^-t

    Fingers crossed someone can help. I've been wrestling with it for a couple of days now.
    Where exactly do you get stuck? Perhaps reading this might help.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Mar 2008
    Posts
    15
    Thanks. I've done most of these now. I've just hit a sticking point with the last one. I've a feeling I've missed something obvious. I've got to...

    1/(s+1)^2(s+2)= A/(s+1) + B/(s+1)^2 + C/(s+2)

    1= A(s+1)(s+2) + B(s+2) + C(s+1)^2

    Let s = -2 Let s = -1

    C = 1 B=1

    Is this right and how do I find A?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by boab View Post
    Thanks. I've done most of these now. I've just hit a sticking point with the last one. I've a feeling I've missed something obvious. I've got to...

    1/(s+1)^2(s+2)= A/(s+1) + B/(s+1)^2 + C/(s+2)

    1= A(s+1)(s+2) + B(s+2) + C(s+1)^2

    Let s = -2 Let s = -1

    C = 1 B=1

    Is this right and how do I find A?
    You can substitute another simple value of s, like s = 0:

    1 = 2A + 2B + C

    And you already know the values of B and C ......
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Mar 2008
    Posts
    15
    I was right then. I had missed something completely obvious!

    Thanks
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Implicit diff question.
    Posted in the Calculus Forum
    Replies: 5
    Last Post: March 4th 2010, 03:26 PM
  2. question about separable diff equation
    Posted in the Differential Equations Forum
    Replies: 5
    Last Post: February 28th 2010, 03:09 AM
  3. implicit diff. question
    Posted in the Calculus Forum
    Replies: 6
    Last Post: December 6th 2009, 10:40 AM
  4. Question with Diff Eq
    Posted in the Differential Equations Forum
    Replies: 4
    Last Post: September 21st 2009, 07:18 PM
  5. Question: what kind of diff. eq is that?
    Posted in the Differential Equations Forum
    Replies: 2
    Last Post: October 26th 2008, 07:08 PM

Search Tags


/mathhelpforum @mathhelpforum