Does the mass of an object affect its momentum? One way to test this idea is to experiment with pendulums. The experiment I chose was to find out if a lighter or heavier pendulum comes to rest more quickly. In order to complete this activity, I engaged the help of my husband and son. The first thing we had to do was find a place to hang the pendulum. As a family, we enjoy doing experiments and building things so we utilized two eyehooks that are in our basement ceiling. We used a spool of string that has a kite hook at the end. We selected washers with three different masses. We confirmed the mass of the washers by using a digital scale. The first challenge we encountered was that we made the string too long. The pendulum was swinging for a very long time. We decided to shorten the string to two feet from the ceiling. The next problem we encountered was deciding what constituted the pendulum stopping. After a few test runs, we realized that the pendulum could swing for a fairly long time. We decided to put a box under the pendulum. On the box we drew a circle with a three inch diameter. We decided that once the pendulum was swinging within the circle we would consider that the end of the trial. Each time we did the experiment we pulled the pendulum back to a height of fifty-seven inches. We did this so that we were sure to test only one variable, the mass of the pendulum. Here are a few pictures of our set up.
As we put the experiment together, we discussed possible outcomes. The two ideas we came up with were that the pendulum with greater mass would have more momentum and would therefore swing longer. The other idea we had was that the washer with a greater mass would be more affected by gravity which would cause it to swing a shorter period of time. After we tested the three pre-selected washers and then we decided to put all three washers on the hook to see what would happen. The following is the data we collected.
Weight of Washer(s) | Swing Time |
59 grams (three washers) | 7:57 minutes |
34 grams (one washer) | 4:58 minutes |
20 grams (one washer) | 4:11 minutes |
5 grams (one washer) | 2:21 minutes |
From our data we discovered that the greater the mass of the pendulum the longer the swing time. We decided that the mass of the pendulum affects its momentum.
If I were going to use this experiment in my class I would set up the pendulum bars, but then I would provide students with lots of different items they could use to answer the question. If I wanted to make this experiment relevant to my students’ lives, I would not have them use pendulums. We would discuss how they think mass and momentum are related. I would then have them design an experiment based on something in their lives to test their ideas. Of course, safety would be crucial to these experiments.
Allowing my students to experience the satisfaction of finding their own ways to answer a question is important to me. For some time, I have been considering ways to improve my students’ problem-solving abilities. I find that many students become easily frustrated when they have to answer questions that are beyond the knowledge level. I think giving students a question and giving them the freedom to design a way to answer the question will encourage students to be creative and resourceful. Hopefully, the feeling of pride that comes from designing their own experiment and finding answers to their questions on their own will encourage them to become more tenacious when faced with a problem. Another goal for using this type of inquiry is that students will see the science concept at work instead of just reading about it in a textbook.
Great activity! I like the idea of drawing the circle on the box to determine the end of the trial. You did a great job controlling your variables. When doing this inquiry activity with students it will be amazing to see how well they control the variables in the experiment. How would you build their background knowledge about pendulums?
ReplyDeleteWow! You did such a great job setting up and executing this experiment.
ReplyDeleteYour write-up was easy to read and understand. I appreciated the inclusion of pictures and the data table. I could easily incorporate this lab in my classroom..thank you for the insight.
ReplyDeleteCarolyn: Thanks for your post. Recently, my students did an activity using the Mercalli scale to rate damage done by a simulated earthquake. In the description for one level of damage it said that pendulum clocks stop. I asked students if they knew what a pendulum was. Only about 5 students raised their hands. I asked how many students had a grandfater clock. Suddenly, almost everyone knew what a pendulum was. I guess I would start background info with this question and then build up to how they work and why they are used.
ReplyDeleteTiffany: Thanks for your comments. My family really had fun doing this experiment. We just bought a new camera so it was a good opportunity to try it out!
ReplyDeleteKelly: I agree that this would be an easy experiment to do in the classroom. I especially like experiments that do not cost very much to perform!
ReplyDeleteHello Jill,
ReplyDeleteI like your suggestion of using washers and am impressed with your addition of photos into your blog. I also had problems deciding what constituded the stopping of the pendulum since it seemed to keep moving forever. The circle was a good idea since the final movement of the pendulum makes a circle and not a swinging motion. I think I will give this suggestion to my students as well.
Thanks, Adam