MCAT Question A Day - 2/17/14 - Answer!
The speed of sound in air at a given temperature is 360 m/s. What is the shortest closed-end pipe that will produce an air column length that can resonate at a frequency of 450 Hz?
A. 20 cm
B. 80 cm
C. 90 cm
D. 125 cm
The correct answer is (A). The shortest pipe length will be associated with the wavelength for the fundamental tone. For a closed-end pipe, this is: wavelength = 4L. The wavelength is the ratio of the speed to the frequency: wavelength = velocity/frequency. Therefore, the shortest length is:
L = velocity / (4*frequency) = (360 m/s) / (4*450/s) = 0.20 m = 20 cm
