A signal f(t) has the Laplace transform F(s) = (−s + 8)/(s² + 7s + 6). Use the initial value theorem to find f(0⁺), the value of f(t) just after t = 0.
Laplace transforms worksheet with answers
1.Easy
F(s) = (−s + 8)/(s² + 7s + 6)
f(0⁺) =
2.Easy
Find the inverse Laplace transform f(t) of F(s) = 16s/(s² + 9) with a table of transform pairs, and evaluate f(0.25).
F(s) = 16s/(s² + 9)t = 0.25 s
f(0.25) =
3.Medium
Find f(t) for F(s) = (s + 11)/(s² + 4s + 29) by completing the square, and evaluate f(0.1).
F(s) = (s + 11)/(s² + 4s + 29)t = 0.1 s
f(0.1) =
4.Medium
Find f(t) for F(s) = (3s + 35)/(s² + 6s + 9) and evaluate f(0.25).
F(s) = (3s + 35)/(s² + 6s + 9)t = 0.25 s
f(0.25) =
5.Hard
A system is described by the differential equation y″ + 4y′ + 3y = 4u′ + 9u, with input u(t) and output y(t). Find its transfer function G(s) = Y(s)/U(s) (zero initial conditions) and evaluate the impulse response g(t) at t = 0.75 s. Find g(0.75).
y″ + 4y′ + 3y = 4u′ + 9ut = 0.75 s
g(0.75) =
6.Hard
A system obeys y″ + 6y′ + 8y = 8·u(t), with y(0) = 3 and y′(0) = 0. At t = 0 a step input u(t) = 4 is applied. Use the Laplace transform to find y(0.6).
y″ + 6y′ + 8y = 8·u(t)y(0) = 3y′(0) = 0u(t) = 4t = 0.6 s
y(0.6) =
Answer key
- 1. f(0⁺) = −1
- 2. f(0.25) = 11.71
- 3. f(0.1) = 1.425
- 4. f(0.25) = 4.487
- 5. g(0.75) = 1.339
- 6. y(0.6) = 3.488
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