to measure the speed of sound in air

Question 1

describe how the length of the column of air was adjusted.

Answer 1

by moving the hollow glass cylinder out of the graduated cylinder of water.

Question 2

describe how the frequency of the column of air was measured.

Answer 2

when the column of air resonates at its fundamental frequency, the frequency of the column of air is the same as that of the tuning fork

Question 3

how was the wavelength of the sound wave measured?

Answer 3

at the fundamental frequency, the length of the pipe closed at one end is equal to one quarter of a wavelength, so 4x(length of the column) is the wavelength of the sound wave

Question 4

describe how the diameter of the column of air was measured.

Answer 4

a vernier callipers is clamped across the diameter of the pipe, and the vernier scale was used to measure the diameter.

Question 5

how was it known that the air column was vibrating at its first harmonic?

Answer 5

begin with the column as small as possible. strike the tuning fork and hold it over the mouth of the pipe. slowly increase the length of the column of air until the loudest sound is heard (the position of resonance). By beginning with a small column and slowly increasing the first instead of second harmonic will be found.

Question 6

using all of the data, what equation can be used to calculate the speed of sound in air

Answer 6

c=4f( l+0.3d)
where c=speed of sound (ms-1)
           F=frequency (Hz)
           L= length of column of air(m)
           D= diameter of pipe (m)

Question 7

why should you repeat the experiment?

Answer 7

to improve the accuracy.

Question 8

why was it necessary to measure the diameter of the air column?

Answer 8

the antinode lies a small distance beyond the open end of the pipe- this “end correction” is approximately 0.3 x diameter of the pipe.

Question 9

another student carried out the experiment. she measured the length of the column of air for each of the first two positions of resonance, but she did not measure the diameter of the air column. explain how this second student would find the speed of sound in air

Answer 9

find distance between first two positions of resonance- this will give a value for half of the wavelength. double this distance to find the wavelength. multiply the wavelength by the frequency to find the speed. (c=f landa)