Question

Find the function f (t) in terms of unit step function in the graph shown below.

(a) 4t [u (t) – u (t + 5)]

(b) 4t [u (t) + u (t + 5)]

(c) 4t [u (t) – u (t – 5)]

(d) 4t [u (t) + u (t – 5)]

I had been asked this question in quiz.

This key question is from Definition of the Laplace Transform in section Intoduction to the Laplace Transform of Network Theory

Answer 1

The correct answer is (c) 4t [u (t) – u (t – 5)]

Easy explanation: The waveform shown in the figure starts at t = 0 and ends at t = 5 sec. In terms of unit step function the waveform can be expressed as f (t) = 4t [u (t) – u (t – 5)].