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Multiple SpringsIf you are using Fathom and the students are analyzing more than one spring, we recommend the students make a separate collection for each spring. Two potential problems are avoided if you have separate collections. First, the students might accidentally treat the case table like a more arbitrary data table. Fathom treats each row in the table as a separate case, whereas the students may set up their own data table so that each row has cases for several springs. If the students copy such a data table directly into Fathom, they will not be able to graph their data the way they want. Make sure the students understand, so they can input their data correctly the first time. Second, with one master collection, graphing the data and calculating stretch becomes much more complex. While having one master collection lets the students graph all their data on a single graph, it makes graphing force vs. stretch much more difficult. If you do want students to use one master collection, however, you will need to introduce them to some advanced tools of Fathom. First, the students need to create a third attribute called spring or springtype. The students will need to record which spring they used in each case. Second, they may need to use conditional arguments in their calculated columns if the springs have different rest lengths. For example, suppose the rest lengths of one long spring and one wide spring used in the lab are 6 cm and 8 cm respectively. To calculate stretch they would use: if (spring = “long”) then (length – 6 cm), otherwise (length – 8 cm) to calculate the stretch correctly for each case. In Fathom, the formula editor will look like this: Third, the students would need to add filters to the graphs to display one spring at a time. This is necessary if you want them to have a force vs. stretch graph and the springs have different rest lengths. 

