Four students and their teacher do an experiment to measure the speed of sound in air. The teacher stands at a distance and fires a starting pistol into the air. The students see the flash when the pistol is fired. They measure the time from when they see the flash to when they hear the bang. A student drew a diagram of the arrangement as shown in Figure 7. The students obtained a value of 240m/s for the speed of sound. The accepted value, in a science data book, is 343 m/s. (i) Calculate the difference between the students’ value and the accepted value as a percentage of the accepted value. (ii) When the distance was 100 m, the students measured the following times: 0.43s 0.35s 0.50s 0.38s Explain why their times vary so much.

GCSE Edexcel Physics Sound: Four students and their teacher

Four students and their teacher do an experiment to measure the speed of sound in air - Edexcel - GCSE Physics - Question 6 - 2020 - Paper 1

Question 6

Four students and their teacher do an experiment to measure the speed of sound in air. The teacher stands at a distance and fires a starting pistol into the air. T... show full transcript

Worked Solution & Example Answer:Four students and their teacher do an experiment to measure the speed of sound in air - Edexcel - GCSE Physics - Question 6 - 2020 - Paper 1

Step 1

Calculate the difference between the students’ value and the accepted value as a percentage of the accepted value.

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Answer

To calculate the percentage difference, we can use the formula:

$\text{Percentage Difference} = \frac{\text{Accepted Value} - \text{Students' Value}}{\text{Accepted Value}} \times 100$

Substituting the values:

$\text{Percentage Difference} = \frac{343 - 240}{343} \times 100$

Calculating this gives:

$\text{Percentage Difference} = \frac{103}{343} \times 100 \approx 30.0\%$

Step 2

Explain why their times vary so much.

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Answer

The variation in the times measured by the students can be attributed to several factors:

Reaction Time: Each student's reaction time can significantly affect the measured time. It is important to note that a typical human reaction time is around 0.5 seconds or less, which is quite large compared to the time taken for sound to travel the distance.
Different Distances: If the students were standing at different distances from the starting pistol, this would affect the travel time of the sound, leading to discrepancies in the measurements.
Perception of Sound: Anticipation of the flash and the sound can also differ among students. Variation in individual perception of the flash and sound can lead to inconsistencies in timing.
Environment: Background noise and weather conditions could further influence how quickly each student perceives the sound.

Four students and their teacher do an experiment to measure the speed of sound in air - Edexcel - GCSE Physics - Question 6 - 2020 - Paper 1

Worked Solution & Example Answer:Four students and their teacher do an experiment to measure the speed of sound in air - Edexcel - GCSE Physics - Question 6 - 2020 - Paper 1

Calculate the difference between the students’ value and the accepted value as a percentage of the accepted value.

Explain why their times vary so much.

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