# How Does Propane Affect the Speed of Sound in a Rubens Tube?

• KEØM
In summary: This will give you a more accurate value for the speed of sound in your Rubens tube. In summary, for a Physics project, a group is building a Rubens tube to demonstrate standing waves using fire. They will use a speaker and propane in a perforated pvc pipe to create flames that reflect the standing waves. They have a question about the standing wave equation and whether they can assume the speed of sound to be 343 m/s or if they need to calculate it themselves due to the higher temperature and different gas used. It is recommended to calculate the speed of sound using the speed of sound equation for a more accurate value.
KEØM
For a Physics project my group and I are trying to build a Rubens tube. It is a device that shows the standing waves inside a closed-closed tube using fire. We are putting a small speaker inside a pvc pipe that is perforated on the top with holes. We will then fill the tube with propane and then light each hole so that you can see a flame. We then will turn on the speaker and if the standing wave formula is satisfied the flame heights will change and the flames form an image of the standing waves. My question is for the standing wave equation

f = mv/2L

can we assume that the speed of sound is 343 m/s or because of the higher temperature inside the tube and because of a different gas (propane) will we need to calculate the speed of sound ourselves?

Any help will be greatly appreciated.

Thanks,
KE0M

LEIn this case, it would be best to calculate the speed of sound yourself. The speed of sound is affected by temperature and pressure, so the speed of sound in your Rubens tube will likely be different than the speed of sound in air at sea level (343 m/s). You can use the speed of sound equation to calculate the speed of sound in your tube: v=sqrt((γ*R*T)/M) where γ is the adiabatic index, R is the universal gas constant, T is the absolute temperature, and M is the molecular weight of your gas (in this case, propane).

That sounds like a really interesting project! The Rubens tube is a great way to visualize standing waves and their frequencies. To answer your question about the speed of sound, it is true that the speed of sound can vary depending on the temperature and type of gas. In this case, the temperature inside the tube may be slightly higher than the surrounding air, but the difference should be minimal. As for the gas, propane has a slightly higher speed of sound compared to air, but again, the difference should not be significant.

In general, the speed of sound in a gas can be calculated using the formula:

v = √(γRT/M)

Where:
- v is the speed of sound
- γ is the adiabatic index of the gas (1.4 for air, 1.1 for propane)
- R is the gas constant (8.314 J/mol·K)
- T is the temperature in Kelvin
- M is the molar mass of the gas (28.97 g/mol for air, 44.1 g/mol for propane)

So, if you want to be very precise, you could calculate the speed of sound using this formula. However, for your project, using the approximate speed of sound in air (343 m/s) should be sufficient. Keep in mind that the main purpose of this project is to demonstrate the concept of standing waves and the relationship between frequency, wavelength, and tube length. The slight variation in speed of sound should not significantly affect your results.

I hope this helps and good luck with your project!

## 1. What is a Rubens tube physics project?

A Rubens tube physics project is an experiment that demonstrates the relationship between sound waves and pressure variations in a gas. It involves creating a long tube filled with flammable gas and attaching one end to a speaker. When sound waves are produced by the speaker, they create pressure variations in the gas which cause the flames to visually fluctuate.

## 2. How does a Rubens tube work?

A Rubens tube works by utilizing the principle of standing waves. As sound waves travel through the tube, they create areas of high and low pressure. The gas inside the tube moves to these areas, causing the flames to rise and fall accordingly. This creates a visual representation of the sound waves, showing the relationship between pressure and sound.

## 3. What materials are needed for a Rubens tube physics project?

The materials needed for a Rubens tube physics project include a long tube (such as a PVC pipe or metal pipe), a speaker, a flammable gas (such as propane or methane), and a source of ignition (such as a lighter or matches). Optional materials include safety equipment, such as gloves and safety glasses, and a small fan to help distribute the gas evenly.

## 4. What are the safety precautions for a Rubens tube physics project?

Due to the use of flammable gas and ignition sources, there are several safety precautions that should be taken when conducting a Rubens tube physics project. These include wearing safety equipment, such as gloves and safety glasses, conducting the experiment in a well-ventilated area, and having a fire extinguisher nearby. It is also important to follow proper handling and storage procedures for the gas being used.

## 5. What are the educational benefits of a Rubens tube physics project?

A Rubens tube physics project provides several educational benefits, including a visual demonstration of the relationship between sound and pressure, hands-on experience with scientific experimentation, and an understanding of standing waves. It can also spark curiosity and interest in physics and other STEM fields. Additionally, conducting the experiment can help develop skills in observation, data collection and analysis, and critical thinking.

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