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HELP Impulse Response h(t) problem

  1. Oct 16, 2006 #1
    HELP!! Impulse Response h(t) problem

    Please help me solve this problem. Atleast the correct answer indication is also very much appreciated.
    Compute the impulse response h(t) for (dy(t))/dt -4y(t)=x(t)
    a. y(t) = e^4t
    b. y(t) = 1- e^4t
    c. y(t) = e^-4t
    d. y(t) = 1- e^-4t
    Compute the impulse response h(t)for (dy(t)/dt -y(t)=dx(t)/dt-2x(t)
    a. y(t) = e^-2t
    b. y(t) = -e^t + delta(lamda)
    c. y(t) = e^-t - delta(lamda)
    d. y(t) = 1- e^-2t
    Compute the impulse response h(t) for (dy(t)/dt +4y(t)=x(t)
    a. y(t) = e^4t
    b. y(t) = 1- e^4t
    c. y(t) = e^-4t
    d. y(t) = 1- e^-4t

    Thanks for your kindness, time and effort.
  2. jcsd
  3. Oct 17, 2006 #2
    hi raihan.
    I'm not sure why you are given y(t) values?
    if you asked to calculate the impulse response of a system say for eample the first onc - you merely make x(t) = delta(t) (i.e. you are inputting an impulse function). You then take the laplace transform of this new expression. You then make Y(s) the subjsect of the formula. Then take the inverse lablace of this which will yield y(t) which is actaully eqaul to h(t). Remember y(t) = h(t) only when we put an mipulse function in the systm - as in this case.

    I 've just realized that this probably multiple choice and you must choose the correct option?? if it's not then it doesn't make sense.

  4. Oct 17, 2006 #3
    Yeah thats right. is multiple choice. And I have to choose the correct option.would you help me please now. Thanks a bunch.
  5. Oct 17, 2006 #4


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    Staff: Mentor

    What are your answers so far, and why do you think they are correct? You must show your own work in order to get our help.
  6. Oct 17, 2006 #5


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    An alternate solution for what LM741 suggested is to calculate the step response s(t) and differentiate it.
  7. Oct 17, 2006 #6
    Generally in impulse response we replaceY[n] with h[n] and x[n] with delta[n] and put different values for n and find the values for the values for h[n]. first we re arrange the equation for h[n] and then find it. but after finding those values what should I do ? I am stuck right there.please help.
  8. Oct 18, 2006 #7


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    The question you presented asks for the impulse response of a continuous system. There is no sense to mention h[n] or x[n].
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