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!

Laplace transorm problem

  1. May 3, 2012 #1
    1. The problem statement, all variables and given/known data
    Using the laplace transform technique, solve the ordinary differential equation:
    d2y/dt2+4.2dy/dt+4.5y=0 initial conditions: y(0)=1 and y'(0)=1


    2. Relevant equations
    From laplace tables:
    d2y/dt2=s2Y-sy(0)-y'(0)
    dy/dt=sY-y(0)


    3. The attempt at a solution
    After using the laplace tables to convert the equation, and rearranging it to make Y the subject, I have come to this point:
    Y=(s+5.2)/s2+4.2s+4.5
    Iv tried completing the square on the denominator and other methods but cannot get to a point that looks similar to the laplace tables in order to convert it back. Im pretty sure i need to use the ones under the section "General approach to quadratic functions of the form as2 + bs + c" however i have completely no idea as to what to do with α and β
     
  2. jcsd
  3. May 3, 2012 #2
  4. May 4, 2012 #3
    Thamkyou for the link, however you cannot factorise the denominator, unless you complete the square. Can you use the partial fraction method with completing the square?
     
  5. May 4, 2012 #4
    Your denominator can certainly complete the square, s^2+4.2s+4.5=(s+2.1)^2-2.1^2+4.5, doesn't it? Obviously no need for partial fraction decomposition :biggrin:
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Laplace transorm problem
  1. Linear Transormation? (Replies: 4)

  2. Laplace Problem (Replies: 2)

  3. Laplace problem (Replies: 2)

Loading...