GATE 2017 EE – Question 60
For a system having transfer function $G(s) = \dfrac{-s + 1}{s + 1}$, a unit step input is applied at time $t = 0$. The value of the response of the system at $t = 1.5$ sec (rounded off to three decimal places) is ________.
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Correct answer: 0.550 to 0.556
Explanation
The output for a unit step is $Y(s) = \frac{1 - s}{s(s + 1)} = \frac{1}{s} - \frac{2}{s + 1}$, so $y(t) = 1 - 2e^{-t}$. At $t = 1.5$ s this is $1 - 2 \times 0.2231 = 0.554$.