A guitarist plucks a string on an electric guitar. The string vibrates and produces a note. Describe the motion of the vibrating string and explain how the terms amplitude, frequency, and period apply to this oscillation.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
When a guitar string is plucked, it oscillates back and forth about its rest position, producing a musical note. The pitch of the note is determined by how rapidly the string vibrates.
Model answer (5 marks)
The string oscillates back and forth about its equilibrium (rest) position.
The amplitude is the maximum displacement of the string from its equilibrium position.
The frequency is the number of complete oscillations of the string per second.
The period is the time taken for one complete oscillation.
Frequency and period are inversely related – the period equals one divided by the frequency (in words).
The amplitude is the maximum displacement of the string from its equilibrium position.
The frequency is the number of complete oscillations of the string per second.
The period is the time taken for one complete oscillation.
Frequency and period are inversely related – the period equals one divided by the frequency (in words).
Examiner tips
- Use the exact terms: amplitude, frequency, period, equilibrium. Show the inverse relationship explicitly. Keep each point short and to the point. Use the word ‘oscillations’ to describe the motion.
- Include the definition of amplitude as a maximum displacement. Mention the rest position. Mention that frequency is per second and period is a time interval.
Common mistakes
- Confusing amplitude with velocity or speed.
- Forgetting to state that the motion is about the equilibrium position.
Mark scheme (5 marks)
- The string oscillates/vibrates about its equilibrium (rest) position
- Amplitude is the maximum displacement of the string from its equilibrium (rest) position
- Frequency is the number of complete oscillations (of the string) per second
- Period is the time taken for one complete oscillation
- Frequency and period are inversely related / period = 1 ÷ frequency (stated in words)
Key terms in this question
amplitude · frequency · period · oscillation
Related
- All AQA A-Level Physics (7408) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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