Some students carry out an experiment to determine the speed of sound. A student stands 75 m75\text{ m}75 m away from a tall brick wall and claps two wooden blocks together. Another student uses a stopwatch to measure the time delay between the clap and hearing the echo.
They repeat the measurement three times and record their results in the table below:
| Distance to wall (m\text{m}m) | Time 1 (s\text{s}s) | Time 2 (s\text{s}s) | Time 3 (s\text{s}s) |
|---|---|---|---|
| 75 | 0.43 | 0.45 | 0.82 |
One of the measurements (Time 3) is anomalous because the student was distracted and stopped the timer late.
Calculate the mean time taken for the sound of the clap to return, using only the suitable values from the table.
Calculate the speed of sound in air. Use your calculated mean time and the equation:
distance travelled=speed×time\text{distance travelled} = \text{speed} \times \text{time}distance travelled=speed×time
Give your answer to 3 significant figures.