## A Laboratory Exercise in Fundamental Units

Discussion: This activity is analogous to the Millikan Oil drop experiment. The Millikan Experiment and the Standard Model both require that students recognize that charge and matter are observed in discrete units.

Purpose: To find the smallest common mass in a set of envelopes.

Procedure: You will be given a number of envelopes. Do not open the envelopes! Measure the mass of each envelope to the nearest 0.1 gram and record the mass on this sheet and on the board in front of the class. Also record the masses of all the other envelopes from your class.

Analysis: List all the envelope masses in ascending order. Envelope #1 will be the lightest. From this list construct a bar graph of envelope mass (vertical axis) as a function of envelope # (horizontal axis) on a separate piece of paper.

Questions:

1. What do you notice about the envelope masses on the finished graph?

2. List the "average" mass for each of the envelope "types."

3. What is the mass difference between the successive averages found in question 2?

4. What does this difference represent? Explain.

Included in the Topics in Modern Physics, May 1990, and Catching the Sun, 1992, Fermilab.