Question: Which pendulum will come to rest more quickly—a lighter pendulum or heavier pendulum?
I tied a string with a washer to the end of a ruler to set-up my pendulum. I taped the ruler to the edge of a table. I released the washer and timed the swings until the pendulum came to a stop. I used three different size washers and repeated my trials three times. Before starting my investigation, I conducted research on pendulums. My research indicated that the length of string was more important than how heavy the object. I still made a prediction that the lighter pendulum would come to rest more quickly. I sat on the floor with a stopwatch and timed the pendulum until I believed it to be stopped.
My results surprised me because I thought the times would be fairly similar, but instead there was a vast difference. My results made question my experiment. I believe my challenge was in determining the precise moment when the pendulum stopped. I sat down until I perceived the pendulum motionless, but this observation was very subjective.
Washer size | Average time to stop |
Large | 6min 36sec |
Medium | 5min 31sec |
Small | 4min 29sec |
The set-up of my pendulum worked extremely well. I students would be able to recreate my pendulum easily. Timing the pendulum did not work well. I wonder if any of my students would find a solution to this problem.
The one modification would be to make this inquiry activity about variables. I would supply my students with different size washers, different length of string, and various materials to create their pendulum. This inquiry lesson will help students understand they are only allowed to change one variable at a time.
Hollie,
ReplyDeleteYou state that your research indicated that the length of string was more important than how heavy the object being swung is so did you at any time vary the length of string to test that theory as well? I think that would give you some insight into that aspect of the activity prior to having your students complete the activity and changing that variable.
As for your timing issue, unfortunately it seems that you may just have to live with the time it takes the pendulum to come to a complete stop. Maybe the thing to do is set up parameters in that the students have to allow the time to run until all back and forth movement has ceased.
Hollie,
ReplyDeleteI too believe that this would be a great inquiry lesson for students to learn about variables and which to change and when. The timing of the swings is very difficult to really evaluate I agree. Could you count the number of swings instead of timing it until it stops? Perhaps that would give you different results?
~Charity
Hollie,
ReplyDeleteI performed the same experiment as you did and experienced the same kind of results. The heavier the bob the more momentum it carried, therefore the longer the bob needed to come to a full rest.
The other variables remained the same; length of string,and the angle of release.
While conducting the investigation I wondered if I changed the angle of release would there be an increase in momentum and therefore longer for the bobs to come rest.
For my fourth graders I think I would prepare a structured inquiry investigation for this lesson because of the number of variables involved. I would introduce one variable at a time to them. Prior to the lesson I would present to the students background knowledge of pendulums and the variables involved.