esTF(s)
e-sTF(s)
$${{Fleft( s
ight)} over {1 + {e^{sT}}}}$$
$${{Fleft( s
ight)} over {1 - {e^{ - sT}}}}$$
Answer is Wrong!
Answer is Right!
The correct answer is $\frac{F(s)}{1-e^{-sT}}$.
The Laplace transform of a function $f(t)$ is defined as
$$L[f(t)] = \int_0^\infty f(t) e^{-st} dt$$
If $L[f(t)] = F(s)$, then the Laplace transform of $f(t-T)$ is
$$L[f(t-T)] = \int_0^\infty f(t-T) e^{-st} dt = \int_T^\infty f(t) e^{-(s-T)t} dt = \int_0^\infty f(t) e^{-st} dt e^{-Ts} = F(s) e^{-Ts}$$
Therefore, the Laplace
transform of $f(t-T)$ is $\frac{F(s)}{1-e^{-sT}}$.Option A is incorrect because it does not take into account
the time delay of $T$. Option B is incorrect because it takes the time delay into account, but it does so incorrectly. Option C is incorrect because it is the Laplace transform of a shifted exponential function, not a delayed exponential function. Option D is correct because it is the Laplace transform of a delayed exponential function.