Random Vibrations

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So far our excitations have been harmonic, periodic, or at least known in advance

These are examples of deterministic excitations, i.e., known in advance for all time

-That is given t we can predict the value of F(t) exactly

Responses are deterministic as well

Many physical excitations are nondeterministic, or random, i.e., can’t write explicit time descriptions
-Rockets
-Earthquakes
-Aerodynamic forces
-Rough roads and seas
The responses x(t) are also nondeterministic