Resonance - How does it occur?

  1. Resonance -- How does it occur?

    I am having a little difficulty with the concept of resonance. Could someone explain how resonance occurs and how elastic oscillation relates to resonance?
     
  2. jcsd
  3. berkeman

    Staff: Mentor

    Sure, we can help out with that. But we require that you show some effort of your own before we can offer tutorial help here. What have you found at wikipedia, Hyperphysics, and other encyclopedia-type websites?

    Please do some reading and research on your own first, and then post links and specific questions here about what you don't understand in what you have read. We are very much about "learning how to learn" here at the PF. :smile:
     
  4. Qualitatively, it is easiest to consider a simple system. Suppose you have a mass on a spring. If you stretch the spring and let go, the mass oscillates, that is vibrates up and down. The mass will vibrate at a fixed frequency. This is the often called the natural frequency. Now suppose we force the mass using a motor (or our hand to vibrate at the resonant frequency (approximately the natural frequency, the details are complicated)). The amplitude (i.e. degree of stretching of the spring) attains it's largest value.

    Forcing at higher or lower frequencies may not achieve as great a stretching. There is more but you may want to read up or reframe your question for more detail.
     
  5. Resonance in action...



    It's easier if the car has no shock absorbers.
     
    Last edited by a moderator: Sep 25, 2014
  6. UltrafastPED

    UltrafastPED 1,918
    Science Advisor
    Gold Member

    Every resonant process is a process which can store energy. If a process cannot store energy, then there cannot be a resonance.

    There are always limits to how much energy can be stored by a resonant process. When these are exceeded you get a breakdown. For example, the Tacoma Narrows bridge disaster was the result of a resonant process:
    http://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)
     
  7. Hold a slinky by the top and let it dangle. Give it a jerk then hold your hand still and you should see the other end oscillate. That's the natural (resonant) frequency for the slinky. If you shake the slinky top up and down at that frequency, the other end oscillates with a large amplitude. If you go too fast or too slow, the slinky doesn't absorb energy, and the bottom of it doesn't move up or down nearly as much.
     
  8. sophiecentaur

    sophiecentaur 13,796
    Science Advisor
    Gold Member

    I endorse what Berkeman says. Tell us what you have found out so far.
     
    Last edited by a moderator: Mar 7, 2014
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