A Ruben?s tube is attached to a small speaker or frequency generator at one end

Question

A Ruben?s tube is attached to a small speaker or frequency generator at one end and the other end to a supply of a flammable gas. Suppose propane (mass = 7.32*10-26 kg, molar mass = 44.1 g/mol) is the gas used as the flammable gas to fill the tube. Propane?s flame temperature in air is 1980oC. At such high temperatures, gases behave as monatomic ideal gases. If the propane fills a Rubens? tube of length 1.25 m, what is the fundamental frequency of a standing wave in the tube? Assume that both ends behave as an open ends in the tube.

Explanation / Answer

Speed of sound = sqrt(k*R*T/M)

where k = adiabatic index (=5/3 for monoatomic gases)

R is gas constant (=8.314)

T is absolute temperature (= 1980+273 = 2253 K)

M is molar mass (= 44.1 *10^-3 kg)

So, velocity of sound = sqrt(5/3 * 8.314*2253/(44.1*10^-3))

= 841.38 m/s

For the first standing wave formed in an open tube, wavelength lambda = length of tube*2

lambda = 2.5 m

velocity = wavelength*frequency

So, fundamental frequency = velocity/wavelength

= 841.38/2.5

= 336.55 Hz

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.