GATE 2020 CH – Question 14
The unit step shown is zero for t < 3 and one for t ≥ 3. Its Laplace transform is
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Correct answer: (A) $e^{-3s}/s$
Explanation
The signal is u(t − 3). Direct integration gives $\mathcal L\{u(t-3)\}=\int_3^\infty e^{-st}dt=e^{-3s}/s$ for Re s > 0. Equivalently, a delay of 3 multiplies the transform 1/s of the unit step by $e^{-3s}$. Thus A.
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