The purpose of this lab is to acquaint the student with the properties of oscillatory motion using an inertial balance, the use of the LabPro motion detector, and data analysis techniques that will show the relationship between the variables for period and mass.

 

 

 

resource lesson	vibration graph waveform graph vibration (or oscillation) amplitude (of oscillation) crest trough period (of oscillation) frequency (of oscillation)
resource lesson	inertia inertial mass gravitational mass weight dynamic measurement static measurement
resource lesson	interpolate extrapolate

 

 

 

Obtain from the equipment table the following items: 1 inertial balance, 1 large black C-clamp, 1 green C-clamp, 1 silver C-clamp, 2 test-tube clamps, and 1 meter stick. A LabPro should already be present on your desk.

 

ALERT! you are NOT to begin your experiment until your instructor has checked the cable connections and power adapter for the LabPro.

 

First use a calibrated triple beam balance to measure the gravitational mass of each clamp to two decimal places. Record your results in Data Table #1 in the designated blanks. Each computer station will have a cardboard box in which to store its equipment. Do NOT switch clamps with other groups! Otherwise, groups from other periods will not longer be able to collect valid data. At the end of the period, return all of your clamps to your station's box.

 

Clamp Description	Gravitational Mass (2 decimal places)
test tube clamp #1
test tube clamp #2
green c-clamp
silver c-clamp

 

Clamp your inertial balance to the edge of your table so that the pan with the "hole" is free to vibrate. Set up your motion probe on a chair so that it "looks at" the edge of the pan. There should be a minimum of 40 cm between the pan and the motion probe. Tape the meter stick to the table approximately 5 cm from the other pan on the opposite side.

 

 

After your apparatus set-up has been cleared by your instructor, launch LoggerPro 3.1 The program should automatically set up graphs according to the connected sensors. With the motion detector properly connected, the program should display graphs of position versus time and velocity versus time. Place the motion detector so that it can watch one side of the inertial balance. When you are ready to obtain data, hit the "Collect" button on the top right-hand side of the program window. 

 

On your screen you should see the inertial balance's location. Displace the balance slightly left or right and make sure that the detector tracks its entire vibration. If part of the motion disappears from the graph, call your instructor over to help you align your probe. When this test checks out, you may begin to gather the actual data for the experiment.

 

Note: Do not allow the balance to vibrate closer than roughly 0.4 meters of the sensor during collection. This will cause faulty returns and skew the data.

 

 

 

You must save your data for each trial before collecting data for the next trial. You are to repeat each mass two times. The information required in Data Table #2 can be gathered from your position-time plot by letting your mouse "hover" over the endpoints of each graph's "good section."

 

 

Start with an empty balance and then add the requested clamp(s) and do two trials with each specified clamp collection. Record the number of vibrations to one decimal place and the time of each crest to three decimal places.

 

	trial number 1			trial number 2
Clamp Descriptions	time crest #1	time last crest	number of vibrations	time crest #1	time last crest	number of vibrations
empty balance
test tube clamp #1
test tube clamp #1 with green c-clamp
green c-clamp with both test tube clamps
both test tube clamps
green c-clamp alone
green and silver c-clamps

 

When you have finished collecting this data, place the motion detector safely back on the table and return your clamps in your group's box to the front instructor's table. At this time, EXIT from LoggerPro 3.1 and complete Data Table #3.

 

	trial number 1			trial number 2
Clamp Descriptions	elapsed time	number of vibrations	average frequency	elapsed time	number of vibrations	average frequency
empty balance
test tube clamp #1
test tube clamp #1 with green c-clamp
green c-clamp with both test tube clamps
both test tube clamps
green c-clamp alone
green and silver c-clamps

 

After completing Data Table #4 you will launch EXCEL and open the file 1-InertialMass.xls.

 

Clamp Descriptions	average frequency #1	average frequency #2	average frequency (hz)	Period T (sec)	Period2 T2 (sec2)	Mass M (kg)
empty balance
test tube clamp #1
test tube clamp #1 with green c-clamp					calculate but do not graph this point
green c-clamp with both test tube clamps
both test tube clamps
green c-clamp alone
green and silver c-clamps

 

 

 

The computer will now graph your data from Data Table #4. Double click My Computer, double click the shared drive called colwell/bay on Lederman, double click your period's folder and then finally double click 1-InertialMass.xls to launch both the file and EXCEL. You will most likely be asked to open the file as "read only" - that is fine. As soon as the file is open, use File Save As to rename the file as

 

LastnameLastnameMass.xls

 

Now input your final AVERAGE values for Mass and Period². As you enter your data, your graph has been preprogrammed and will grow. Mass (M), measured in kg to 5 decimal places; will be placed on the x-axis and Period² (T²), measured in sec² to 3 decimal places, will be placed on the y-axis. Remember to NOT ENTER the data for the trial using the green C-clamp and test-tube clamp #1. When your graph is finished, be certain that any points that are obviously out-of-line have been rechecked for accuracy - either in measurement, or for a mistake in typing.

 

Remember to resave your file and close. Then go to your teacher's station and obtain a printout of your graph.