DP Physics Questionbank
B.4 – Forced vibrations and resonance (HL only)
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Description
Nature of science:
Risk assessment: The ideas of resonance and forced oscillation have application in many areas of engineering ranging from electrical oscillation to the safe design of civil structures. In large-scale civil structures, modelling all possible effects is essential before construction. (4.8)
Understandings:
- Natural frequency of vibration
- Q-factor and damping
- Periodic stimulus and the driving frequency
- Resonance
Applications and skills:
- Qualitatively and quantitatively describing examples of under-, over- and critically-damped oscillations
- Graphically describing the variation of the amplitude of vibration with driving frequency of an object close to its natural frequency of vibration
- Describing the phase relationship between driving frequency and forced oscillations
- Solving problems involving Q factor
- Describing the useful and destructive effects of resonance
Guidance:
- Only amplitude resonance is required
Data booklet reference:
International-mindedness:
- Communication through radio and television signals is based on resonance of the broadcast signals
Utilization:
- Science and technology meet head-on when the real behaviour of damped oscillating systems is modelled
Aims:
- Aim 6: experiments could include (but are not limited to): observation of sand on a vibrating surface of varying frequencies; investigation of the effect of increasing damping on an oscillating system, such as a tuning fork; observing the use of a driving frequency on forced oscillations
- Aim 7: to investigate the use of resonance in electrical circuits, atoms/molecules, or with radio/television communications is best achieved through software modelling examples
Directly related questions
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16N.3.HL.TZ0.14a:
Explain, with reference to energy in the system, the amplitude of oscillation between
(i) t = 0 and tA.
(ii) tA and tB.
- 16N.3.HL.TZ0.14b: The system is critically damped. Draw, on the graph, the variation of the displacement with time...
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17M.3.HL.TZ1.10b:
Calculate the Q factor for the system.
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17M.3.HL.TZ1.10c:
The Q factor of the system increases. State and explain the change to the graph.
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17M.3.HL.TZ2.11b.i:
State and explain the displacement of the sine wave vibrator at t = 8.0 s.
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17M.3.HL.TZ2.11b.ii:
The vibrator is switched off and the spring continues to oscillate. The Q factor is 25.
Calculate the ratio for the oscillations of the spring–mass system.
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17M.3.HL.TZ1.10a:
State what is meant by damping.
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17M.3.HL.TZ2.11a:
On the graph, sketch a curve to show the variation with driving frequency of the amplitude when the damping of the system increases.
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20N.3.HL.TZ0.12c(ii):
The sphere oscillates vertically within the oil at the natural frequency of the sphere-spring system. The energy is reduced in each cycle by . Calculate the factor for this system.
- 17N.3.HL.TZ0.12b: Outline what change would be required to the value of Q for the mass–spring system in order for...
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17N.3.HL.TZ0.12a:
Explain why it would be uncomfortable for the farmer to drive the vehicle at a speed of 5.6 m s–1.
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18M.3.HL.TZ1.11b.ii:
calculate the Q at the start of the motion.
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18M.3.HL.TZ1.11a:
Describe the motion of the spring-mass system.
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18M.3.HL.TZ2.11a:
Draw a graph to show the variation of amplitude of oscillation of the system with frequency.
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18M.3.HL.TZ2.11b:
The Q factor for the system is reduced significantly. Describe how the graph you drew in (a) changes.
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18N.3.HL.TZ0.11a:
State and explain the direction of motion of the mass at this instant.
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18N.3.HL.TZ0.11b:
The oscillator is switched off. The system has a Q factor of 22. The initial amplitude is 10 cm. Determine the amplitude after one complete period of oscillation.
- 19M.3.HL.TZ2.14c: The damping of the bridge system can be varied. Draw, on the graph, a second curve when the...
- 19M.3.HL.TZ2.14b: Outline, with reference to the curve, why it is unsafe to drive a train across the bridge at 30 m...
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19M.3.HL.TZ2.14a:
Show that, when the speed of the train is 10 m s-1, the frequency of the periodic force is 0.4 Hz.
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19M.3.HL.TZ1.11b:
Another system has the same initial total energy and period as that in (a) but its Q factor is greater than 25. Without any calculations, draw on the graph, the variation with time of the total energy of this system.
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19M.3.HL.TZ1.11a:
The Q factor for the system is 25. Determine the period of oscillation for this system.
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19N.3.HL.TZ0.10c:
The point of suspension now vibrates horizontally with small amplitude and frequency 0.80 Hz, which is the natural frequency of the pendulum. The amount of damping is unchanged.
When the pendulum oscillates with a constant amplitude the energy stored in the system is 20 mJ. Calculate the average power, in W, delivered to the pendulum by the driving force.
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19N.3.HL.TZ0.10b:
After one complete oscillation, the height of the pendulum bob above the rest position has decreased to 28 mm. Calculate the Q factor.
- 19N.3.HL.TZ0.10a: Describe what is meant by damped motion.
