Question: Which pendulum will come to rest more quickly – a lighter pendulum or a heavier pendulum?
Hypothesis: I think that a lighter pendulum on a 15cm. string will come to rest faster than a heavier pendulum on a 15cm. string.
Materials: 3 washers of different masses, string, scissors, stop watch, ruler, and balance
Manipulated (Independent) Variable: size of washer for pendulum
Responding (Dependent) Variable: length of time for pendulum to come to a stop
Controlled Variables: same length of string for all pendulums, same stopwatch and time keeper, same chair to test pendulum and same release point for all pendulums
Time it takes for pendulum to come to rest
Mass of Washer | Trial 1 | Trial 2 | Trial 3 |
2g. | 52 sec. | 1 min. 53 sec. | 3 min. 3 sec. |
6g. | 1 min. 51 sec. | 1 min. 31 sec. | 2 min. 58 sec. |
16 g. | 51 sec. | 1 min. 50 sec. | 3 min. 7 sec. |
I expected these results because objects with a heavier mass have a greater momentum. Objects with a greater mass are harder to start moving and harder to stop moving.
Overall the experiment went well. I experienced few challenges during this guided inquiry. I decided early what question I would focus on. I gathered the materials that I would need and created time to complete the experiment. I carefully considered the variables for this experiment. The manipulated variable was the size of the washer, which was used as the object hanging from the pendulum. The responding variable was the length of time for the pendulum to stop, come to rest. I had many controlled variables for this experiment. Each pendulum had the same length of string. I used the same stop watch, the same chair to test the pendulum and the same release point. I conducted the experiment in my kitchen. The time for the lightest pendulum to come to rest was 52 seconds. I repeated the experiment three times. During the second trial, it took much longer for the pendulum to come to rest, a minute longer. I realized that my husband had opened the screen door and a breeze was blowing through the kitchen, causing the pendulum to keep moving. This was the only challenge that I encountered. I did learn from this and how this could cause the results to be invalid.
To get a different result using the same question, I would change the length of the string so that it was not the same length for all of the trials.
I would set this experiment up similar for my students. I would let the students decide what object they would use at the end of the pendulum. To relate this to student’s lives, I would have them compile a list of everyday objects that come to rest from a state of motion, and apply the law of Inertia. This experiment is easy to do and all materials are readily available. Students would not have to actually find the mass of the objects’ if a scale was not available. They could tell which object was heavier or lighter by holding them.
I would like for my students to learn that they could solve any problem by carrying out an experiment. In some ways scientists are like detectives, piecing together clues to learn about a process or event.
