Under Damped

(noun)

"The condition in which damping of an oscillator causes it to return to equilibrium with the amplitude gradually decreasing to zero; system returns to equilibrium faster but overshoots and crosses the equilibrium position one or more times. "

Related Terms

  • Over Damped
  • Critically Damped

Examples of Under Damped in the following topics:

  • Damped Harmonic Motion

    • A door shutting thanks to an under damped spring would sway in the door way, briefly continuing to open and close.
    • Let the damping force be proportional to the mass' velocity by a proportionality constant, b, called the vicious damping coefficient.
    • The physical situation has three possible results depending on the value of a, which depends on the value of what is under our radical.
    • $\gamma^2 > 4\omega_0^2$ is the Over Damped case.
    • $\gamma^2 < 4\omega_0^2$ is the Under Damped case.
  • Damped transient motion

    • The fluid will damp out the motion, more or less depending on whether it has the viscosity of water or honey.
    • This looks like the equation of a damped sinusoid.
    • First if $\frac{\gamma}{2\omega_0} < 1$ , corresponding to small damping, then the argument of the square root is positive and indeed we have a damped sinusoid.
    • In this case the motion is said to be "over-damped" since there is no oscillation.
    • The borderline case $\gamma = 2 \omega_0$ is called critical damping, in which case $x(t) = x_0 e^{-\frac{\gamma}{2} t}$ .
  • Forced Vibrations and Resonance

    • At first the finger is held steady, and the ball bounces up and down with a small amount of damping.
    • In real life, most oscillators have damping present in the system.
    • It is interesting that the widths of the resonance curves shown in depend on damping: the less the damping, the narrower the resonance.
    • The more selective the radio is in discriminating between stations, the smaller its damping.
    • The narrowest response is also for the least amount of damping.
  • Driven Oscillations and Resonance

    • Driven harmonic oscillators are damped oscillators further affected by an externally applied force.
    • If a frictional force (damping) proportional to the velocity is also present, the harmonic oscillator is described as a damped oscillator.
    • Driven harmonic oscillators are damped oscillators further affected by an externally applied force F(t).
    • \omega_0$, and the damping ratio $\!
    • Describe a driven harmonic oscillator as a type of damped oscillator
  • Back EMF, Eddy Currents, and Magnetic Damping

    • Back EMF, eddy currents, and magnetic damping are all due to induced EMF and can be explained by Faraday's law of induction.
    • Eddy currents can produce significant drag, called magnetic damping, on the motion involved.
    • A common physics demonstration device for exploring eddy currents and magnetic damping.
    • (c) There is also no magnetic damping on a nonconducting bob, since the eddy currents are extremely small.
    • Explain the relationship between the motional electromotive force, eddy currents, and magnetic damping
  • Forced motion with damping

    • The causes of damping are extremely subtle.
    • Try extending a damping piston of the sort used on doors.
    • where $\gamma$ is a constant reflecting the strength of the damping.
    • \label{damping} }$
    • Square of the amplitude factor for forced, damped motion near a resonance $\omega_0$.
  • Power

    • The shock absorber is analogous to the resistance damping and limiting the amplitude of the oscillation.
    • The forced but damped motion of the wheel on the car spring is analogous to an RLC series AC circuit.
    • The shock absorber damps the motion and dissipates energy, analogous to the resistance in an RLC circuit.
  • Simple harmonic oscillation

    • That's just under 1.3 oscillations per second, or 1.3 Hz.
    • Thus the total force on the mass (spring + gravity, but no damping for now) is mg $- k(\Delta l + x)$.
    • So far we have not accounted for the damping of the spring.
  • Exercises

    • For the characteristic frequency you estimated above, what is the minimum damping required to ensure that the mass does not oscillate if you pull it down and let it go.
    • With this minimum (or "critical") damping, how long will it take for the mass to come to rest?
    • (a) What is the damping constant ( $\gamma$ ) for the circuit?
  • Forced motion

    • Free oscillations are also called transients since for any real system in the absence of a forcing term, the damping will cause the motion to die out.
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