Find the inverse Laplace transform f(t) of F(s) = 7/(s + 4) − 4/s with a table of transform pairs, and evaluate f(0.2).
Laplace transforms worksheet with answers
1.Easy
F(s) = 7/(s + 4) − 4/st = 0.2 s
f(0.2) =
2.Easy
A signal f(t) has the Laplace transform F(s) = 17/(s(s² + 3s + 13)). Use the final value theorem to find the value f(∞) that f(t) settles to.
F(s) = 17/(s(s² + 3s + 13))
f(∞) =
3.Medium
Find f(t) for F(s) = (2s + 3)/(s² + 6s + 9) and evaluate f(0.2).
F(s) = (2s + 3)/(s² + 6s + 9)t = 0.2 s
f(0.2) =
4.Medium
Find f(t) for F(s) = (5s + 30)/(s² + 4s + 40) by completing the square, and evaluate f(0.5).
F(s) = (5s + 30)/(s² + 4s + 40)t = 0.5 s
f(0.5) =
5.Hard
Solve y″ + 7y′ + 10y = 0 with y(0) = 10 and y′(0) = −4 using the Laplace transform, and find y(0.5).
y″ + 7y′ + 10y = 0y(0) = 10y′(0) = −4t = 0.5 s
y(0.5) =
6.Hard
A system obeys y″ + 9y′ + 20y = 120·u(t). It starts at rest (y(0) = 0, y′(0) = 0) and the input is a step u(t) = 1 for t ≥ 0. Use the Laplace transform to find the output y(0.1).
y″ + 9y′ + 20y = 120·u(t)u(t) = 1y(0) = 0, y′(0) = 0t = 0.1 s
y(0.1) =
Answer key
- 1. f(0.2) = −0.8547
- 2. f(∞) = 1.308
- 3. f(0.2) = 0.7683
- 4. f(0.5) = −1.648
- 5. y(0.5) = 5.203
- 6. y(0.1) = 0.4471
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