Which pendulum will come to rest more quickly--a lighter pendulum or a heavier pendulum? When beginning this inquiry, I honestly did not know the answer to this question. I thought that the greater mass of the pendulum would definitely cause it to swing with more momentum, but was not sure if this greater amount of weight would end up stopping the pendulum sooner. I made the hypothesis that a greater weight would cause the pendulum to stop moving sooner than the pendulum with the lighter weight. I gathered the materials to make a homemade pendulum. I used string and two nails with very different masses. My first attempts at measuring the amount of time the pendulum swung made me realize that I had to be more precise in my experiment. In order to only change one variable I had to control all others. I realized I had to attach the nail to the same place on the string so that the length of each pendulum was equal. The only thing I wanted to change in my experiment was the mass of the nail. I decided to test each nail three times and compare each nail’s average time.
As I watched and felt the first nail swing on the pendulum, I noticed that it was moving quickly, but losing height quickly. After three trials, I came to the conclusion that the lighter mass allowed the pendulum to swing quickly, but because it did not have much mass, it slowed each period. The second nail had more mass. I repeated the same procedure for the second nail and quickly realized that it was moving slower. The mass on the end of the pendulum seemed to give it an added boost, like a child swinging their legs while swinging. Although this pendulum was moving slowly, it was not losing height nearly as fast. I could feel that the mass of the nail was giving it an advantage over the first nail.
My hypothesis was incorrect. Through experimentation I learned that a greater mass means that an object will be harder to stop. “Momentum is defined as the product of the mass of an object and its velocity” (Tillery, Enger & Ross, 2008, p. 43). Since I was beginning the nails at the same height and simply releasing them from the same pendulum, the nail with the greater mass caused the pendulum to move with greater momentum. Because the lighter pendulum did not have as much mass, it came to rest more quickly.
Before completing this experience I struggled to identify how to make my pendulum a different mass without altering the air resistance. I chose the nails because they were such different masses. I could have used the washers because they were similar sizes and shapes, but I thought they did not provide a big enough difference in mass to be effective. I worried that simply holding the string was not a scientific enough procedure, but I think that feeling the differences in the masses help explain why the object with the greater mass continues swinging longer than the pendulum with the lighter mass. I think that students should be made aware of the fact that they must make sure they hold the string still and in the same spot, but having them hold the pendulum will help them feel why the pendulum with the greater mass swings longer than the lighter one.
I think that having my students engage in a guided inquiry experience would build skills that would make them more scientifically literate. I want my students to move past memorizing definitions and explanations to higher levels of understanding. Designing their own investigation to answer a question will help students take their knowledge to the next level. Though they have read about the scientific method and that only one variable in the experiment can be changed, they do not realize the importance of these concepts until they have the freedom to investigate on their own. During my investigation, I discovered that I needed to think about how to control all the variables but one. My students would experience the effects and confusion of results if they do not set up the investigation properly.
Guided inquiry “is most successful when students have had numerous opportunities to learn and practice different ways to plan experiments and record data” (Banchi & Bell, 2005). I definitely could not have my students do this guided inquiry experience on their own tomorrow. Although I see the benefits of having students design their own experiments, I understand that it takes much practice to get to this point. I could however, do this investigation in front of the class. I could take suggestions for what materials to use, what procedures to follow, and have students analyze and record the data. This sort of whole class practice will help my students build the skills and confidence they need to design and carry out an investigation of their own. “Students need to experience science through direct experience, consistently practicing the inquiry skills and seeking deeper understandings of science content through their investigations” Banchi & Bell, 2005).