1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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 Transform question with unit step function

  1. May 7, 2015 #1
    1. The problem statement, all variables and given/known data


    2. Relevant equations
    Laplace Trasformations

    3. The attempt at a solution
    a. done
    b. f(t)= t -3*t*u(t-1) + 4*u(t-1) -3*u(t-2) -2*t*(t-2)
    c. 1/(s^2) - (3e^-s -2e^-2s)/(s^3) + (4e^-s -3e^-2s)/s
    d. 1/(s-1) * (1/(s^2) - (3e^-s -2e^-2s)/(s^3) + (4e^-s -3e^-2s)/s)

    These are the answers i got but my friend got all different ones and we are not sure who is correct. Thanks for any help.
  2. jcsd
  3. May 7, 2015 #2

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    The first 4 terms on the right of (b) are OK but the fifth term is incorrect. You should develop the habit of always checking these things for yourself; just look at f(t) and your right-hand-side for 0 < t < 1, then for 1 < t < 2, then for t > 2. What does your answer in (b) look like for t > 2?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Threads - Laplace Transform question Date
Quick laplace transform question Oct 19, 2015
Laplace transformation question Apr 24, 2015
Laplace Transform Question Dec 31, 2013
LaPlace Transform question #2 Apr 13, 2013
LaPlace Transform question #1 Apr 13, 2013