A signal f(t) has the Laplace transform F(s) = (6s + 4)/(s² + 7s + 5). Find the initial slope f′(0⁺) with the initial value theorem.
Laplace transforms worksheet with answers
1.Easy
F(s) = (6s + 4)/(s² + 7s + 5)
f′(0⁺) =
2.Easy
A signal f(t) has the Laplace transform F(s) = 19/(s(s² + 6s + 24)). Use the final value theorem to find the value f(∞) that f(t) settles to.
F(s) = 19/(s(s² + 6s + 24))
f(∞) =
3.Medium
F(s) = (5s + 30)/(s² + 9s + 20). Its inverse transform has the form f(t) = A·e−4t + B·e−5t. Find the coefficient A by partial fractions.
F(s) = (5s + 30)/(s² + 9s + 20)
A =
4.Medium
Find f(t) for F(s) = (4s + 38)/(s² + 10s + 25) and evaluate f(0.4).
F(s) = (4s + 38)/(s² + 10s + 25)t = 0.4 s
f(0.4) =
5.Hard
Solve y″ + 5y′ + 6y = 0 with y(0) = 9 and y′(0) = 15 using the Laplace transform, and find y(0.6).
y″ + 5y′ + 6y = 0y(0) = 9y′(0) = 15t = 0.6 s
y(0.6) =
6.Hard
A system obeys y″ + 7y′ + 10y = 15·u(t). It starts at rest (y(0) = 0, y′(0) = 0) and the input is a step u(t) = 10 for t ≥ 0. Use the Laplace transform to find the output y(0.4).
y″ + 7y′ + 10y = 15·u(t)u(t) = 10y(0) = 0, y′(0) = 0t = 0.4 s
y(0.4) =
Answer key
- 1. f′(0⁺) = −38
- 2. f(∞) = 0.7917
- 3. A = 10
- 4. f(0.4) = 1.516
- 5. y(0.6) = 7.195
- 6. y(0.4) = 5.12
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