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Creating Models

Free and forced vibrations, damping and resonance

  • 2 things to know
  • Components 01, 02 and 03

Overview

Recall questions on free and forced vibrations, natural frequency, damping, lightly damped, critically damped and overdamped motion, resonance and resonance curves, how damping changes the peak, the phase at resonance, observing resonance with a mass on a spring and Barton's pendulums, useful and harmful resonance, and damped car suspension.

What you need to know

Answer each one before you reveal it.

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Key term

What is the effect of increasing the damping on a resonance curve?

Key term

What is the phase relationship between the driver and the driven system at resonance?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is a free vibration?

    Model answer

    It is the oscillation of a system left to move at its own natural frequency after being displaced and released, with no driving force.

  2. 2

    What is a forced vibration?

    Model answer

    It is oscillation produced by a periodic driving force, at the frequency of the driver rather than the natural frequency of the system.

  3. 3

    Define the natural frequency of an oscillating system.

    Model answer

    It is the frequency at which the system oscillates freely after being displaced and released.

  4. 4

    What is damping?

    Model answer

    It is the removal of energy from an oscillating system by resistive forces, so that the amplitude falls with time.

  5. 5

    Describe the motion of a lightly damped oscillator.

    Model answer

    It keeps oscillating at close to its natural frequency while the amplitude decreases gradually over many cycles.

  6. 6

    What happens to a critically damped system displaced from equilibrium?

    Model answer

    It returns to equilibrium in the shortest possible time without overshooting and oscillating.

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