Today, accelerometers are found everywhere and are in nearly all of our handheld devices. Thus, every student with a smartphone possesses these scientific instruments and can use them to take data. However, they are packaged in a small chip, and their function and data can be tricky to understand.1 For example, it can cause confusion as it reads “1g,” where g is the acceleration due to gravity, 9.8 m/s2, in the vertical direction, when it is just sitting there not moving, and only reads zero in free fall. We have created a simple, low-cost, yet reasonably functional model2 of an accelerometer using a tennis ball and its clear container, some electrical tape, and a plastic spring toy often found in party favors.

The model can be seen in Fig. 1. We calibrated ours with marks at ±1g and 0g, which...

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