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Mechanical Resonance

Mechanical Resonance. Natural frequency is the frequency that a system will oscillate / vibrate once it has been set into motion (given some energy and left alone). It depends on the its mass, shape, centre of mass and the material it is made from. (sometimes called resonant frequency).

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Mechanical Resonance

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  1. Mechanical Resonance Natural frequency is the frequency that a system will oscillate / vibrate once it has been set into motion (given some energy and left alone). It depends on the its mass, shape, centre of mass and the material it is made from. (sometimes called resonant frequency) next: damping

  2. Un-damped SHM damped SHM highly damped SHM

  3. Sometimes the oscillations happen due to the application of an external periodic force, then they are ‘driven oscillations’ or ‘forced oscillations’. In this case the system oscillates at a different frequency, a combination of the natural frequency and the driving frequency.

  4. Here the driving frequency is out of phase with the natural frequency. natural frequency of the system driving frequency of the applied force resultant frequency of the driven system

  5. Here the driving frequency is in phase with the natural frequency. natural frequency of the system driving frequency of the applied force resultant frequency of the driven system RESONANCE happens

  6. The mass-spring system is attached to a vibration generator which is forcing it to oscillate (driving it). We are varying the frequency of the vibration generator (driving frequency) and measuring the maximum amplitude of the oscillation each time. This mass-spring system has a natural frequency of 3Hz. Plotting a graph of the maximum amplitude of the driven system vs the driving frequency gives this graph: If the system was heavily damped maximum amplitude / m 0 1 2 3 4 5 6 driving frequency / Hz

  7. maximum amplitude / m 0 1 2 3 4 5 6 driving frequency / Hz When the driving frequency is below or above the natural frequency of the system, the amplitude is low. When the driving frequency is equal to the natural frequency, the amplitude can be much higher This ‘high amplitude response’ is called ‘resonance’ Resonance is the large amplitude oscillations that arise as a result of an oscillatory system being driven at a frequency equal to its natural frequency. for highly damped systems, resonance becomes less noticeable. Destructive resonance happens when the high amplitudes cause permanent damage to the system.

  8. The gravitational field strength g on the Moon is one sixth that on Earth. A pendulum with a period of 1 s on Earth, would have, on the moon a period of : a. 1/6 s b. 1/√6 s c. √6 s d. 6 s

  9. A particle performs simple harmonic motion, has a period of 2 seconds and an amplitude of 4m. • The maximum acceleration of the particle is • a. Π ms-2 • 4 Π ms-2 • Π2 ms-2 • Π2 ms-2

  10. A lorry driver notices that the image in the rear-view mirror is blurred when the engine runs slowly and becomes clear as the engine speed is increased. • This is an example of • superposition • resonance • polarisation • coherence

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