®
M o d e l N o . M E - 6 9 8 9
E x p e r i m e n t 9 : R e s o n a n c e
49
6.
Add one 0.5 kg mass to the cross beam at the end of the apparatus to balance it.
7.
Tie the mass hanger to the free end of the string and add one 0.5 kg mass.
Sensor setup
You will use the load cell to measure the vibration of the string. The software will
display a fast Fourier transform (FFT) of the data to show the fundamental frequency.
1.
Connect the load cell to port 1 of the load cell amplifier. Connect the load cell
amplifier to your computer interface. Set up the software to display an FFT of
force (see note 6 on page 66).
2.
Lift the hanging mass so that there is no tension on the string and press the zero
button on the load cell amplifier. Replace the mass.
Pre-lab questions
1.
With a total of 1 kg of hanging mass (the hanger plus a 0.5 kg mass), guess the
frequency at which the string will vibrate when you pluck it.
2.
Will increasing the hanging mass cause the frequency to increase or decrease?
Procedure
1.
Start data monitoring. (With the software displaying an FFT, clicking the
Start
button will make DataStudio monitor and display data, but not record it.)
2.
Pluck the string. When you see a clear peak on the FFT display, stop data
monitoring to “freeze” the display. If you do not see a peak, or do not stop data
monitoring at the right moment, pluck the string and try again.
3.
In a table, write down the hanging mass and the fundamental frequency.
4.
Add another 0.5 mass.
5.
Repeat steps 1 through 4 to collect data for 8 different values of hanging mass.