Question

Carry out a simple activity to measure the speed of sound, along with a friend in a large open ground of size 200 m or more. (This activity is to be facilitated by the teacher.)

1. Your friend stands at one end of the open ground with the balloons, while you stand at the other end with the stopwatch.
2. Signal your friend to burst one balloon. When you see the balloon burst, start the stopwatch. As soon as you hear the ‘pop’ sound of the bursting balloon, stop the timer and note down the reading.
3. Repeat this experiment multiple times and take the average value of the times noted.
4. Note the approximate distance between you and your friend using a map application on a mobile phone.
5. Divide the distance measured with the average time to get the average speed of sound. What value of speed did you get from the experiment? Compare it with the speed of sound in air, which is typically about (346 $$\mathrm{~m} \mathrm{~s}^{-1})$$ at 25 °C. 6.
6. Why did you measure the time between ‘seeing’ and ‘hearing’ the balloon burst?

Answer 1

Given:

Speed of sound wave ($v$) = 340 m/s

Distance for two wavelengths ($2\lambda$) = 8 cm

1. Wavelength ($\lambda$):

$$2\lambda = 8 \text{ cm}$$

$$\lambda = 4 \text{ cm}$$

$$\lambda = 0.04 \text{ m}$$

2. Frequency ($f$):

$$f = \frac{v}{\lambda}$$

$$f = \frac{340}{0.04}$$

$$f = 8500 \text{ Hz}$$

The correct wavelength is 0.04 m, and the correct frequency is 8500 Hz.