Motion and Variables

Pendulums

Explanation of Experiment

  • The independent variables are mass, release position, and length.
  • The dependent variable are the number of pendulum swings in 15 seconds.
  • There are three levels, the mass, length and release positions.
  • The constant is pendulum.
  • The mass and release position are the controls.

Materials

  • Strings at different lengths
  • Pennies
  • Paper Clips
  • Number Chart
  • Pencils
  • Stopwatch
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Steps in the Lesson

1.Have students tape a pencil 5 cm from their desks.

2.Pass out materials to each group: pennies, stopwatch, strings of different lengths, paper clips, masking tape, and a ruler.

3.Students will connect the paper clip to the strings and adding a penny to the paper clip to create their pendulums.

4.Students will measure out the lengths of their strings in the following degrees: 13 cm, 17 cm, 20 cm, 25cm, 33cm, 55 cm, 90 cm, 170 cm.

5.After they measure out each length, have them make a loop at the end of the string and tape the loop in place.

6.Students will test their hypothesis of how many swings the pendulum will make in 15 seconds. Record answer in data table

7. Students will create their standard with a length of 38 cm.

8.Have students make their predictions of the amount of swings the pendulum will make when changing the release positions.

9.Students will test their release position changing from 0 to 45.Set stopwatch for 15 seconds and record data.

10.Students will change the mass of the pendulum by adding two pennies to a single paper clip. Have students make predictions of number of swings and record data.

11.Set stopwatch for 15 seconds and record data.

12.Students will then make six changes in length. They will go back to one penny and use the different lengths of strings.

13.They will make predictions of how many swings the pendulums will complete for each length and test their hypotheses using the stopwatch for 15 seconds.

14.Tape the number chart on a wall in the classroom and have each group hang their pendulum under the number of swings completed.

Analysis of Data

The reasoning we did this experiment was to focus on the idea of changing the mass, length, or release position of the pendulum have an affect on the numbers of swings the pendulum completes in a unit of time. We concluded when doing the experiment that as the length of the pendulum increases, the number of swings decreases and if the length is shorter than the pendulum swings increases. Along with this, we were able to see that mass and release position had no effect on the number of swings. We recorded the data on a data table then converted the information to the picture graph. Related to the scientific theory of cause and effect, the length of the pendulum effects the number of swings.The patterns that show us this are seen in the data table. The arch of pendulum is visible in the picture graph. (Seen above)

Teaching Notes

Related to the scientific theory of causes and effect, the length of the pendulum effects the number of swings. Some alternative conceptions students can have include that the mass of the pendulum will affect how many swings occurs in a given amount of time. To tackle this idea, have students increase the mass, or pennies, to show that the mass has no effect on the number of swings.

Scaffolding
To test student's knowledge after the experiment, have them journal their answer to the question "How does changing the mass, length, or release position effect the number of swings the pendulum completes in a unit of time?" Using a concept map on cause and effect can also assess their understanding of this experiment. This can allow the teacher to information needed to determine if there needs to be any reteaching done.