# Keep in Time

#### Summary

## Learning Goals

Students will:

- Describe why the clappers don't all clap at the same time

- Calculate the speed of sound in air

- (optional) Make a graph of distance vs. time of the claps
- (optional) Relate the slope of the graph to the speed of sound
- (optional) Find meaning in the y-intercept of the graph

## Context for Use

## Description and Teaching Materials

Here is a worksheet (Microsoft Word 2007 (.docx) 2.5MB Aug24 14) to guide students through this activity:

worksheet solutions (Microsoft Word 2007 (.docx) 3MB Aug24 14)

These instructions have medium scaffolding, giving students fairly detailed instructions, but requiring students to determine the best way to measure the speed of sound in air. An instructor may chose to provide less detailed instructions to encourage independent thinking and problem solving.

## Teaching Notes and Tips

Students who watch this video sometimes think that the students in the video were waiting until they heard the metronome beat to react, but they weren't, they were clapping together with the periodic beats they heard. * *

If you have the time, I would encourage you to have your students try the graphing method. The results turn out closer to the expected value, it makes sense to use the data from all of the students (not just the first and the last one), and I think that the particular way that the data deviate from a straight line is especially instructive.