Laplace Transform question with unit step function

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SUMMARY

The discussion revolves around the application of the Laplace Transform to a function involving a unit step function, specifically f(t) = t - 3t*u(t-1) + 4u(t-1) - 3u(t-2) - 2t(t-2). The correct Laplace Transform is derived as 1/(s^2) - (3e^-s - 2e^-2s)/(s^3) + (4e^-s - 3e^-2s)/s. A critical error identified in the fifth term of the function prompts the suggestion to verify the function across different intervals of t to ensure accuracy.

PREREQUISITES
  • Understanding of Laplace Transformations
  • Familiarity with unit step functions (u(t))
  • Knowledge of exponential functions in the context of Laplace Transforms
  • Ability to analyze piecewise functions
NEXT STEPS
  • Study the properties of Laplace Transforms in detail
  • Learn how to apply the unit step function in Laplace Transforms
  • Practice deriving Laplace Transforms for piecewise functions
  • Explore the verification of solutions through interval analysis
USEFUL FOR

Students studying differential equations, engineers applying Laplace Transforms in control systems, and anyone seeking to understand the application of unit step functions in mathematical modeling.

jamesdocherty
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Homework Statement



upload_2015-5-7_19-12-23.png


Homework Equations


Laplace Trasformations

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.
 
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jamesdocherty said:

Homework Statement



View attachment 83171

Homework Equations


Laplace Trasformations

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.

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?
 

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