Laplace transform with step function

In summary, the differential equation y'+2y=f(t) with initial condition y(0)=0 can be solved using Laplace transforms. The function f(t) can be represented as a step function, with a value of t for 0 ≤ t < 1 and a value of 0 for t ≥ 1. When taking the Laplace transform, the domain of integration should be split into (0,1) and [1, infinity], resulting in an integral of te^-st over the interval (0,1).
  • #1
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Homework Statement



[tex]y'+2y=f(t), y(0)=0, where f(t)=\left\{t, 0\leq t<0 \;and \; 0, t \geq 0[/tex] (I don't know how to do piecewise)

Homework Equations



Equation for initial conditions; step function: u(t-a)

The Attempt at a Solution



I know how to solve a differential equation with initial conditions using Laplace transforms, I just don't know what f(t) looks like as a step function, or how it would behave. would it be t*u(t-1)?
 
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  • #2
f(t) looks like 0 for all values of t, are you sure your definition of f(t) is correctly copied down?
 
  • #3
Opps, it's:
[tex]t, \; 0 \leq t < 1[/tex]
[tex]0, \; t \geq 1[/tex]
 
  • #4
OKay, then when taking the Laplace transform of the RHS, split the domain of integration to (0,1) and [1, infintity], the part where you integrate over 0 to infinity will vanish and you will be left with:
[tex]
\int_{0}^{1}te^{-st}dt
[/tex]
 

1. What is the Laplace transform of a step function?

The Laplace transform of a step function is equal to 1/s, where s is the complex variable in the Laplace domain. This can be derived by using the definition of the Laplace transform and integrating a step function over time.

2. How is the Laplace transform used with step functions in real-world applications?

The Laplace transform with step functions is commonly used in control systems engineering to analyze the stability and response of systems to sudden changes or inputs. It is also used in signal processing to analyze signals that have a sudden change in amplitude at a specific time.

3. Can the Laplace transform be applied to a step function with a non-zero initial value?

Yes, the Laplace transform can be applied to a step function with a non-zero initial value. The initial value can be incorporated into the Laplace transform by adding a term in the transform expression that takes into account the initial value at the time of the step.

4. What is the inverse Laplace transform of a step function in the time domain?

The inverse Laplace transform of a step function is equal to the Heaviside step function, also known as the unit step function. This is a function that is equal to 0 for negative values and 1 for positive values, starting at the time of the step.

5. What is the significance of the Laplace transform of a step function in the study of differential equations?

The Laplace transform of a step function is significant in the study of differential equations because it can be used to solve initial value problems. By taking the Laplace transform of a differential equation, it can be transformed into an algebraic equation which can be solved using standard techniques. The inverse Laplace transform can then be applied to obtain the solution in the time domain.

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