Guided Inquiry Lesson: Pendulum

I recently conducted a guided inquiry lesson to determine whether a lighter or heavier pendulum would come to rest more quickly. A basic experiment was set up to gather enough data in order to draw an accurate conclusion.

To build the base of the pendulum, two identical quart containers were used. Both containers were filled with water to ensure they would be stable enough for conducting this experiment. The containers were placed ten inches apart, and a twelve-inch wooden ruler was attached to the top of them using duct tape. A string was attached at the midpoint of the ruler with an excess of ten inches for attaching a weight. Three different size washers were used as weights and consisted of the following masses: 1.1g, 8.2g, and 16.4g.

To ensure accurate results, each washer was tested three times.

When testing each washer, they were attached to the string and placed on top of a small box that was 7 ¾ inches in height.

The box was slowed moved away until the washer fell off, due to the force of gravity, and the pendulum was in motion. The pendulum with the 1.1g washer remained in motion for an average of three minutes and thirteen seconds. When using the 8.2g washer, the pendulum remained in motion even longer with an average of four minutes and fifty-one seconds. The 16.4g washer caused the pendulum to remain in motion the longest with an average of six minutes and thirty-nine seconds. Based on these results, it can be concluded that a lighter pendulum will come to rest more quickly than a heavier pendulum. These were the results I expected.

This experiment could easily be modified by changing the length of the string before attaching the washer. Also, a pendulum could easily be built using different materials. Before I use this lesson with my third grade students, I need to ensure they fully understand why the only variable that should be changed is the size and mass of the washer. I think my students would really enjoy designing and building their own pendulums. This would be a great lesson to teach them about Newton's second law. Plus students would be able to understand how friction from the air eventually causes the pendulum to come to a rest.