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Signals and Systems - Engineering

Q1:

If a signal g(t) has energy E, then the energy of the signal g(2t) is equal to ...

A E/2

B E/4

C E

D 2E

ANS:A - E/2

I will be using int as a symbol for integration.

E = int( f(t)^2 dt )
now
E' = int ( f(2t)^2 dt )
if 2t = x
E' = int ( f(x)^2 dx ) / 2
E' = E / 2.
So it has half the energy.