Damped Harmonic Oscillator
The Newton's 2nd Law motion equation is
This is in the form of a homogeneous second
order differential equation and has a
solution of the form
Index
Substituting this form gives an auxiliary
Periodic
equation for λ
motion
concepts
The roots of the quadratic auxiliary equation
are
Damping coefficient
Undamped oscillator
Driven oscillator
The three resulting cases for the damped
oscillator are
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Damping Coefficient
Index
Periodic
When a damped oscillator is subject to a damping force which is linearly
dependent upon the velocity, such as viscous damping, the oscillation will
have exponential decay terms which depend upon a damping coefficient. If motion
the damping force is of the form concepts
then the damping coefficient is given by
This will seem logical when you note that the damping force is proportional
to c, but its influence inversely proportional to the mass of the oscillator.
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Underdamped Oscillator
Index
Periodic
motion
concepts
Reference
Barger &
Olsson
For any value of the damping coefficient γ less than the critical damping
factor the mass will overshoot the zero point and oscillate about x=0. The
behavior is shown for one-half and one-tenth of the critical damping factor.
Also shown is an example of the overdamped case with twice the critical
damping factor.
Note that these examples are for the same specific initial conditions, i.e., a
release from rest at a position x0. For other initial conditions, the curves
would look different, but the the behavior with time would still decay
according to the damping factor.
Damped Oscillator Further details for underdamped case
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Underdamped Oscillator
When a damped oscillator is underdamped, it approaches zero faster than in
the case of critical damping, but oscillates about that zero.
The equation is that of an
exponentially decaying
sinusoid.
Index
Periodic
The damping coefficient is less motion
than the undamped resonant concepts
frequency . The sinusoid
frequency is given by
but the motion is not strictly
periodic.
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