Lecture #8: Damped/driven oscillators

Question 1

The driving force comes from where?

Answer 1

The operator, not the system

Question 2

Why do we not have a phase term when we describe the forcing?

Answer 2

Because the forcing defines what a zero-phase means

Question 3

The response of an oscillator driving at a frequency w is an oscillation with frequency

Answer 3

w

Question 4

Consider the non-resonant case where the system is undamped and the driving frequency is very small. What is the phase?

Answer 4

0

Question 5

Consider the non-resonant case where the system is undamped and the driving frequency is very large. What is the phase?

Answer 5

pi

Question 6

Consider an undamped, driven system where the driving frequency equals the natural frequency. What happens to the amplitude?

Answer 6

Approaches infinity

Question 7

Why does the amplitude diverge when driving = natural frequency?

Answer 7

The system will keep absorbing energy continuously

Question 8

At resonance, what is the phase between position and forcing?

Answer 8

Position is a quarter cycle behind forcing

Question 9

The forcing has to be in phase with the

Answer 9

Velocity

Question 10

Consider an undamped, driven system. When is the forcing power a maximum?

Answer 10

When the force and the velocity are in phase

Question 11

Power

Answer 11

F dot v