4.3+FORCED+OSCILLATION+AND+RESONANCE

Back to IB PHYSICS > OSCILLATIONS AND WAVES =4.3 FORCED OSCILLATIONS AND RESONANCE= 4.1 KINEMATICS OF SHM 4.2 ENERGY CHANGES DURING SHM 4.4 WAVE CHARACTERISTICS 4.5 WAVE PROPERTIES
 * 1 Measure || 2 Mech || 3 Therm || 4 Waves || 5 Electric || 6 Fields || 7 Atomic || 8 EPCC || 9 MIF || 10 Therm AHL || 11 Wave Phen || 12 EMI || 13 QNP || 14 Digital || OPT || PRAC || REVISE ||

State what is meant by damping.



DAMPING: The loss of energy of oscillations due to work against friction or viscous medium. Can be heavy (over), light (under) or critical.

It is sufficient for students to know that damping involves a force that is always in the opposite direction to the direction of motion of the oscillating particle and that the force is a dissipative force.

Describe examples of damped oscillations. [|DAMPED OSCILLATIONS SIMULATION] Change the damping and observe critical damping. Leaving the other variables unchanged, try different whole number values of b and screenshot the graph each time until you identify the critical damping situation. Compare under-, over- and critical damping situations.

Reference should be made to the degree of damping and the importance of critical damping. A detailed account of degrees of damping is not required. TACOMA BRIDGE media type="custom" key="25910910"

State what is meant by natural frequency of vibration and forced oscillations. NATURAL FREQUENCY: The frequency at which a system will oscillate naturally. FORCED OSCILLATIONS: Oscillations of a system which is being driven at another frequency than its natural one. media type="custom" key="25959522"

Describe graphically the variation with forced frequency of the amplitude of vibration of an object close to its natural frequency of vibration. Students should be able to describe qualitatively factors that affect the frequency response and sharpness of the curve.

State what is meant by resonance. [|RESONANCE SIMULATION APPLET] - observe how the amplitude varies as the forcing frequency approaches the natural frequency. Leaving the other variables constant, change the exciter frequency starting at 1.0 rad/s by intervals of 0.5 rad/s. Observe how the amplitude reached depends on the match between forcing frequency and natural frequency. Finally, observe the phase of the forced oscillation in relation to the forcing oscillation.

RESONANCE: When the driving oscillation has the same frequency as the natural frequency of the system, the amplitude of the system will increase. media type="custom" key="25959528" Describe examples of resonance where the effect is useful and where it should be avoided.

ACTIVITY: Make a webpage using pictures and text (no more than 200 well-chosen words) on an example of resonance. Mention the ideas of **natural frequency; forced oscillations; driving frequency; energy transfer; damping**
 * Microwave generators/ ovens - see PHET sim
 * A particular musical instrument
 * Vibrations in machinery
 * Tuning a radio
 * An opera singer smashing a glass
 * The Millennium Bridge over the river Thames
 * Quartz oscillator
 * Earthquakes
 * Feedback
 * Tesla's oscillators
 * Tidal resonance
 * NMR
 * MRI - see PHET
 * Greenhouse gases
 * Orbital resonance
 * The laser

Examples may include quartz oscillators, microwave generators and vibrations in machinery. media type="custom" key="25959536"

media type="custom" key="12676216" **RESONANCE EXAMPLES RESEARCHED BY IB PHYSICS HL 2012**