This weeks lab is a simple experiment meant to introduce the concept of experimental uncertainty and basic ideas about statistics that will be useful in later labs. Students work in pairs to test each others reaction time by dropping a ruler while the other student catches it as quickly as possible. If the student trying to catch the ruler starts with his or her fingers positioned at "zero" the reaction time can be calculated from the freefall equations and the distance the ruler fell as measured by where the students fingers were on the ruler after catching it.
Issues to emphasize in this lab include the limited precision of the measurement of distance (students should reflect this in the number of significant digits in their data) and the use of Excel to calculate statistical properties of data.