Plucked Rulers

Students use photogates with pendulum timing mode on LabQuest interfaces to measure the period of a ruler clamped to a table and plucked. The photogates offer very high precision, so there's little value in many repeated trials at a single overhang length — instead, push students to collect data at many different lengths or conditions. The lab doesn't fill the full session on its own, so press groups to gather ample data and begin planning a second experiment for the following week.

Students should have a working experiment with rough initial analysis done by the end of the first session. Remind them that most experimental designs don't survive first contact with the equipment, so early testing matters.

For the second week, calculate presentation time in advance (about 3 minutes per group plus transitions) and communicate a clear cutoff for when experiments must wrap up. Presentations are informal — no slides, just explanation — with all group members participating.

The scoring rubric can be treated as an interim score in the first week, replaced by the second week's score if it improves. This gives students two full weeks to meet the goals without the pressure of two separate deadlines.

A makeup option for absent students: provide them with data sets from multiple groups and have them calculate and interpret t′ for various combinations, identifying which data best addresses whether the chosen factor affects the period. Expect about two hours for this analysis.

This is the fourth and fifth lab in a ten-lab introductory physics sequence focused on waves, oscillations, and sound. It follows three weeks of spring experiments (Springs 1–3) where students develop foundational skills in data collection, uncertainty, comparing data sets, and identifying relationships between variables. By this point students should be comfortable with basic statistical comparisons and have encountered the distinction between objective measurement and subjective interpretation.

The rulers unit introduces scientific integrity and bias mitigation as new themes layered on top of those existing skills. It also serves as the first experience with student-directed experimental design, where groups choose their own variable and methodology.

After this unit, students move to a Tones lab investigating sound, then to a multi-week independent investigation project where they formulate their own research questions and present findings. The mini-presentations at the end of the rulers unit serve as deliberate preparation for those later formal presentations. The follow-up homework asks students to begin brainstorming testable questions for the independent project.