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 5. The students obtained a value of 240 m/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 0.55s 0.38s Explain why their times vary so much.

GCSE Edexcel Physics Combined Science 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 Combined Science - Question 4 - 2020 - Paper 1

Question 4

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. Th... 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 Combined Science - Question 4 - 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 use the formula:

ext{percentage difference} = \frac{(\text{students' value} - \text{accepted value})}{\text{accepted value}} \times 100

Substituting the values:

\text{percentage difference} = \frac{(240 - 343)}{343} \times 100

Calculating the difference:

\text{percentage difference} = \frac{-103}{343} \times 100 \approx -30\\%

The final result shows a percentage difference of approximately 30%.

Step 2

Explain why their times vary so much.

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Answer

There are several factors that could contribute to the variation in measured times:

Reaction Time: Each student has a different reaction time, which is the time taken to see the flash and respond to it. This can lead to variations especially if the difference exceeds 0.5 seconds.
Distance from the Starting Pistol: Each student may be standing at slightly different distances from the starting pistol, affecting the time it takes for the sound to reach them.
Environmental Factors: Factors such as wind, temperature, and humidity can affect sound propagation, leading to differences in perceived sound arrival times.
Perception Differences: Students may have different acuity for light or sound, affecting their ability to perceive the flash and the bang simultaneously.

Four students and their teacher do an experiment to measure the speed of sound in air - Edexcel - GCSE Physics Combined Science - Question 4 - 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 Combined Science - Question 4 - 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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