Resonance is the tendency of a system to vibrate at a maximum amplitude at the natural frequency
of the system.
Resonance takes place when a system is made to vibrate at its natural frequency as a result of vibrations
that are received from another source of the same frequency. In the following investigation you willmeasure the speed of sound using resonance.
Experiment : using resonance to measure the speed of sound
Aim:
To measure the speed of sound using resonance
Apparatus:
one measuring cylinder
a high frequency (512 Hz) tuning fork
some water
a ruler or tape measure
Method:
Make the tuning fork vibrate by hitting it on the sole of your shoe or something else that has a rubbery texture.
A hard surface is not ideal as you can more easily damage the tuning fork. Be careful to hold the tuning fork by its handle. Don't touch the fork because it will damp the vibrations.
Hold the vibrating tuning fork about 1 cm above the cylinder mouth and start adding water to the cylinder
at the same time. Keep doing this until the first resonance occurs. Pour out or add a little water until you find the levelat which the loudest sound (i.e. the resonance) is made.
When the water is at the resonance level, use a ruler or tape measure to measure the distance (
) between the top of the cylinder
and the water level.
Repeat the steps
[link] above, this time adding more water until you find the next resonance.
Remember to hold the tuning fork at the same height of about 1 cm above the cylinder mouth and adjust the water levelto get the loudest sound.
Use a ruler or tape measure to find the new distance (
) from the top of the cylinder to the new water level.
Conclusions:
The difference between the two resonance water levels (i.e.
) is half a wavelength, or the same as
the distance between a compression and rarefaction. Therefore, since you know the wavelength, and you know the frequencyof the tuning fork, it is easy to calculate the speed of sound!
Interesting fact
Soldiers march out of time on bridges to avoid stimulating the bridge to vibrate
at its natural frequency.
A 512 Hz tuning fork can produce a resonance in a cavity where the air column is 18,2 cm long. It can also produce
a second resonance when the length of the air column is 50,1 cm. What is the speed of sound in the cavity?
Remember that:
We have values for
and so to calculate
, we need to first find
.
You know that the difference in the length of the air column between two resonances is half a wavelength.
From the investigation you will notice that the column of air will make a sound at a certain length.
This is where resonance takes place.
Music and sound quality
In the sound chapter, we referred to the quality of sound as its
tone. What makes the tone of a note played on an instrument?When you pluck a string or vibrate air in a tube, you hear mostly the fundamental frequency. Higher harmonics are present, but are fainter. These are called
overtones . The tone of a note depends on its mixture of overtones. Different instruments have different
mixtures of overtones. This is why the same note soundsdifferent on a flute and a piano.
Let us see how overtones can change the shape of a wave:
The resultant waveform is very different from the fundamental
frequency. Even though the two waves have the same mainfrequency, they do not sound the same!
Summary - the physics of music
Instruments produce sound because they form standing waves in strings or pipes.
The fundamental frequency of a string or a pipe is its natural frequency. The wavelength
of the fundamental frequency is twice the length of the string or pipe when both ends are fixed or both ends are open. It is four times the length of the pipe when one end is closed and one end is open.
When the string is fixed at both ends, or the pipe is open at both ends the first harmonic is formed when the standing wave forms one whole
wavelength in the string or pipe. The second harmonic is formed when thestanding wave forms 1
wavelengths in the string or pipe.
When a pipe is open at one end and closed at the other, the first harmonic is formed when the standing wave forms
wavelengths in the pipe.
The frequency of a wave can be calculated with the equation
.
The wavelength of a standing wave in a string fixed at both ends can be calculated using
.
The wavelength of a standing wave in a pipe with both ends open can be calculated using
.
The wavelength of a standing wave in a pipe with one end open can be calculated using
.
Resonance takes place when a system is made to vibrate at its natural frequency as a
result of vibrations received from another source of the same frequency.
Waveforms
Below are some examples of the waveforms produced by a flute, clarinet and saxophone for different frequencies (i.e. notes):
End of chapter exercises
A guitar string with a length of 70 cm is plucked. The speed of a wave in the string is 400 m
s
. Calculate the frequency of the first, second, and third harmonics.
A pitch of Middle D (first harmonic = 294 Hz) is sounded out by a vibrating guitar string. The length of the string is 80 cm. Calculate the speed of the standing wave in the guitar string.
The frequency of the first harmonic for a guitar string is 587 Hz (pitch of D5). The speed of the wave is 600 m
s
. Find the length of the string.
Two notes which have a frequency ratio of 2:1 are said to be separated by an octave. A note which is separated by an octave from middle C (256 Hz) is
254 Hz
128 Hz
258 Hz
512 Hz
Playing a middle C on a piano keyboard generates a sound at a frequency of 256 Hz. If the speed of sound in air is 345 m
s
, calculate the wavelength of the sound corresponding to the note of middle C.
What is resonance? Explain how you would demonstrate what resonance is if you have a measuring cylinder, tuning fork and water available.
A tuning fork with a frequency of 256 Hz produced resonance in an air column of length 25,2 cm and at 89,5 cm. Calculate the speed of sound in the air column.
Questions & Answers
Three charges q_{1}=+3\mu C, q_{2}=+6\mu C and q_{3}=+8\mu C are located at (2,0)m (0,0)m and (0,3) coordinates respectively. Find the magnitude and direction acted upon q_{2} by the two other charges.Draw the correct graphical illustration of the problem above showing the direction of all forces.
To solve this problem, we need to first find the net force acting on charge q_{2}. The magnitude of the force exerted by q_{1} on q_{2} is given by F=\frac{kq_{1}q_{2}}{r^{2}} where k is the Coulomb constant, q_{1} and q_{2} are the charges of the particles, and r is the distance between them.
Muhammed
What is the direction and net electric force on q_{1}= 5µC located at (0,4)r due to charges q_{2}=7mu located at (0,0)m and q_{3}=3\mu C located at (4,0)m?
Capacitor is a separation of opposite charges using an insulator of very small dimension between them. Capacitor is used for allowing an AC (alternating current) to pass while a DC (direct current) is blocked.
Gautam
A motor travelling at 72km/m on sighting a stop sign applying the breaks such that under constant deaccelerate in the meters of 50 metres what is the magnitude of the accelerate
velocity can be 72 km/h in question. 72 km/h=20 m/s, v^2=2.a.x , 20^2=2.a.50, a=4 m/s^2.
Mehmet
A boat travels due east at a speed of 40meter per seconds across a river flowing due south at 30meter per seconds. what is the resultant speed of the boat
which has a higher temperature, 1cup of boiling water or 1teapot of boiling water which can transfer more heat 1cup of boiling water or 1 teapot of boiling water explain your . answer
I believe temperature being an intensive property does not change for any amount of boiling water whereas heat being an extensive property changes with amount/size of the system.
Someone
Scratch that
Someone
temperature for any amount of water to boil at ntp is 100⁰C (it is a state function and and intensive property) and it depends both will give same amount of heat because the surface available for heat transfer is greater in case of the kettle as well as the heat stored in it but if you talk.....
Someone
about the amount of heat stored in the system then in that case since the mass of water in the kettle is greater so more energy is required to raise the temperature b/c more molecules of water are present in the kettle
pratica A on solution of hydro chloric acid,B is a solution containing 0.5000 mole ofsodium chlorid per dm³,put A in the burret and titrate 20.00 or 25.00cm³ portion of B using melting orange as the indicator. record the deside of your burret tabulate the burret reading and calculate the average volume of acid used?
No. According to Isac Newtons law. this two bodies maybe you and the wall beside you.
Attracting depends on the mass och each body and distance between them.
Dlovan
Are you really asking if two bodies have to be charged to be influenced by Coulombs Law?
Specific heat capacity is a measure of the amount of energy required to raise the temperature of a substance by one degree Celsius (or Kelvin). It is measured in Joules per kilogram per degree Celsius (J/kg°C).
AI-Robot
specific heat capacity is the amount of energy needed to raise the temperature of a substance by one degree Celsius or kelvin
ROKEEB
Got questions? Join the online conversation and get instant answers!