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An experiment was set up to investigate how the fundamental frequency of a stretched string varied with its length - Leaving Cert Physics - Question 3 - 2018
Question 3
An experiment was set up to investigate how the fundamental frequency of a stretched string varied with its length. The length / l and the frequency f of the string... show full transcript
Worked Solution & Example Answer:An experiment was set up to investigate how the fundamental frequency of a stretched string varied with its length - Leaving Cert Physics - Question 3 - 2018
Step 1
Draw a labelled diagram of the apparatus used in this experiment.
Answer
The diagram should include the following components:
- String - represent the length of the string suspended between two supports, such as a bridge.
- Tuning Fork/Frequency Generator - used to initiate vibrations in the string.
- Bridge - where the string is anchored at both ends.
- Measuring Instruments - like a ruler to measure the length of the string.
- Means of Tensioning - such as weights or a tuning peg to adjust tension.
- Resonance Detection - which could be paper or a magnet that shows maximum amplitude.
- Sonometer - if applicable for measuring frequency.
Ensure that each component is clearly labelled according to the marking scheme.
Step 2
Step 3
Describe how the string was set vibrating.
Answer
The string was set vibrating by striking a tuning fork and placing it on the bridge of the string. This action transfers vibrations from the tuning fork to the string, causing it to resonate. Alternatively, the string can be plucked using a finger or a plectrum, which also sets it into vibration, creating sound waves.
Step 4
How was the frequency of the string determined?
Answer
The frequency of the string was determined by measuring the vibrations using either a frequency meter or an electronic tuner. The readings were taken when the string was resonating at its fundamental frequency, often by matching the frequency of the tuning fork or the frequency generator used in the experiment.
Step 5
Sketch a graph to show the relationship between / l and f that you would expect to obtain.
Answer
The graph should show:
- y-axis labelled as
f(frequency) - x-axis labelled as
1/l(inverse of length)
The expected relationship is:
- A hyperbolic decline indicating that as the length of the string increases, the frequency decreases.
- Start with a plot point at higher frequencies for shorter strings, gradually curving downwards to lower frequencies for longer strings. Ensure the graph has a clear relationship and one axis is correctly labelled.