Quantized Mass Printer Friendly Version
Purpose

To let each student become familiar with measuring with a triple beam balance and to develop critical thinking skills. Secondly, to introduce student to a technique of data analysis using linear regression.

Measuring Masses

Each group of two will receive 10 envelopes containing identical index cards.

NOTE: If there are not enough balances, one group at a time should measure their envelopes. It ought to not take more than 5-8 minutes get the 10 mass measures. After each group is through with the balance, they can return to their own computer/lab station to complete their analysis and let a second group use the balance.

After zeroing your triple beam balance, measure the mass of each of the 10 envelopes. In the table below, record the number of cards identified as being in each envelope and the sealed envelope's mass. Do NOT open any of your envelopes. Two envelopes will be identified only by letters. Measure and record their masses and then place their values in the last two rows of the data chart.

 Envelope # or letter Mass (g) 1 2 3 4 5 6 7 8 9 10

Analysis.

EXCEL will now graph your data. To reach the template, open the physics shared drive using the icon on your desktop. Locate your period's folder and open the template 1-mass.xls. 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

QuantizedMass-LastnameLastname.xls

in your period's folder. This copy of the file now belongs uniquely to your group. Remember that there are to be no spaces in the file name.

 What is the name of your file?

Input your values for the number of cards and the mass of each envelop into the spreadsheet. (Do not enter the information from the envelope that has a letter instead of a number). As you enter your data, its graph will grow. 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. Update your saved file and print a copy of the data table and graph for each group member.

Conclusions.

 What was the numerical value of your line's slope?

 What was the numerical value of your line's y-axis intercept?

 What is the equation of your line using the variables M for mass and N for the number of cards?

Refer to the following information for the next two questions.

Use the equation of your line to answer the following questions. Place your answers on your graph's printout as well as in this form.
 What is the significance of the slope of the line? That is, what physical property does it represent?

 What is the significance of the y-axis intercept of your line? That is, what physical property does it represent?

Refer to the following information for the next four questions.

Use the equation of your line to experimentally determine the number of cards in your "lettered" envelope. Remember that you are not allowed to open any envelopes. Show any required calculations on the bottom of your graph printouts.
 Our letter was ___.

 It's mass was ____ grams.

 It contained ____ cards

 In physics we often refer to quantities being "quantized." For example, charged objects can only carry an electric charge that is an integer multiple of the fundamental charge (1 |e| = 1.6 x 10-19 coulombs). This tells us that a charged object could never have a charge of 12.5|e| or 20 x 10-19 coulombs. Give an example of a mass reading that would not have not been valid in this experiment. Explain your reasoning.

Lab Report. After you have submitted your online form, turn in your individual calculations for your conclusions to the one-way box.