## Pendulum Time

This lesson explores how the pendulum has been a reliable way to keep time for centuries. Students work in teams to build their own working clock using a pendulum. They will need to be able to speed up and slow down the motion of the pendulum clock.

• Learn about timekeeping and engineering.
• Learn about engineering design and redesign.
• Learn how engineering can help solve society’s challenges.
• Learn about teamwork and problem solving.

Age Levels: 8-18

### Build Materials (For each team)

Required Materials

• String
• Rubber balls, golf balls, ping pong balls, or ball, fishing weight (to use as pendulum weight)
• Pencil
• Aluminum foil
• Paper cups
• Paper clips
• Wire
• Plastic or paper plates
• Glue
• Pipe cleaners
• Pvc piping
• Cardboard
• Paper
• Velcro

#### Testing Materials & Process

Materials

• Clock design
• Stopwatch

Process

Teams test their clock design by demonstrating how the pendulum swings at a faster and slower speed. They will need to be able to record time with their clock and set up their own scale or chart to keep track of the pendulum movements. Use a stopwatch to see how many swings of the pendulum occur in 10 seconds. They will also need to speed up or slow down their clock.  (Hint: adjusting the length of string attached to the pendulum might assist with this task.)

#### Engineering Design Challenge

Design Challenge

You are part of a team of engineers who have been given the challenge of building a working clock based on a pendulum.  You’ll need to be able to set the clock at two speeds, and will have to figure out how to adjust the materials you are using to make the clock run faster and slower.

Criteria

• Must be able to set the clock at two speeds.

Constraints

• Use only the materials provided.
• Teams may trade unlimited materials.

#### Activity Instructions & Procedures

1. Break class into teams of 3-4.
2. Hand out the Pendulum Time worksheet, as well as some sheets of paper for sketching designs.
3. Discuss the topics in the Background Concepts Section. To introduce the lesson, consider asking the students how important it is to have a way to accurately measure time. Ask them to observe all the different types of clocks and time measuring devices they have at school and at home.
Explain that a pendulum is relatively simple, and consists of only a few components: a length of string or wire, a bob or some type of weight, and a fixed point where it is attached to a solid object.  A string may swing in various directions, but for the clock, they will want to fix it to something, or use another material to keep the motion along a single plane — back and forth, not wobbling.
4. Review the Engineering Design Process, Design Challenge, Criteria, Constraints and Materials.
5. Provide each team with their materials.
6. Explain that students must design and build a working clock based on a pendulum. They will need to be able to set the clock at two speeds, and will have to figure out how to adjust the materials they are using to make the clock run faster and slower.
7. Announce the amount of time they have to design and build (1 hour recommended).
8. Use a timer or an on-line stopwatch (count down feature) to ensure you keep on time. (www.online-stopwatch.com/full-screen-stopwatch). Give students regular “time checks” so they stay on task. If they are struggling, ask questions that will lead them to a solution quicker.
9. Students meet and develop a plan for their clock. They agree on materials they will need, write/draw their plan, and present their plan to the class. Teams may trade unlimited materials with other teams to develop their ideal parts list.
Tell students that their clock doesn’t need to be perfect, but does need to be able to measure time fairly consistently.  They can keep a chart or measurements of the “period of the pendulum” — which is the amount of time that it takes a pendulum to complete one full back-and-forth swing.
10. Teams build their designs. They should be sure to measure the length of the string they plan to use to attach their weight in order to form a pendulum. They will need to keep track of this when they are adjusting the speed at which their pendulum moves. They may wish to weigh their pendulum weight as well, to help them set their clock to work at two different speeds
11. Teams test their clock design by demonstrating how the pendulum swings at a faster and slower speed. They will need to be able to record time with their clock and set up their own scale or chart to keep track of the pendulum movements. Use a stopwatch to see how many swings of the pendulum occur in 10 seconds. They will also need to speed up or slow down their clock. (Hint: adjusting the length of string attached to the pendulum might assist with this task.)
12. As a class, discuss the student reflection questions.
13. For more content on the topic, see the “Digging Deeper” section.

Variations

For younger students, simplify the lesson by having the string/wire taped or tied to a chair frame, and just have them observe and record with a stopwatch the constancy of the pendulum motion.

For older students, require a gear system or escapement, so the pendulum is a working part of a larger mechanism.

Extension Activity

Have students build a working metronome that can keep a beat at equal time intervals. Have students explore the concept of isochronism.

Student Reflection (engineering notebook)

1. How similar was your original design to the actual clock your team built?
2. If you found you needed to make changes during the construction phase, describe why your team decided to make revisions.
3. Was your clock able to measure time at two different speeds? What measurement scale did you devise to measure time with your clock?
4. Which clock that another team made was the most effective or interesting to you? Why?
5. Do you think that this activity was more rewarding to do as a team, or would you have preferred to work alone on it? Why?
6. If you could have used one additional material (tape, glue, wood sticks, foil — as examples) which would you choose and why?

#### Time Modification

The lesson can be done in as little as 1 class period for older students. However, to help students from feeling rushed and to ensure student success (especially for younger students), split the lesson into two periods giving students more time to brainstorm, test ideas and finalize their design. Conduct the testing and debrief in the next class period.

#### Engineering Design Process

Divide into teams
Review the challenge and criteria constraints
Brainstorm possible solutions (sketch while you brainstorm!)
Choose best solution and build a prototype
Test then redesign until solution is optimized
Reflect as a team and debrief as a class

#### Background Concepts

Parts of a Pendulum

A pendulum is relatively simple, and consists of only a few components: a length of string or wire, a bob or some type of weight, and a fixed point where it is attached to a solid object. Remember that a string may swing in various directions, but for the clock, you’d want to fix it to something, or use another material to keep the motion along a single plane — back and forth, not wobbling.

#### Dig Deeper

Internet Connections

• Time’s Pendulum: From Sundials to Atomic Clocks, the Fascinating History of Timekeeping and How Our Discoveries Changed the World (ISBN: 978- 0156006491)
• The Pendulum: A Case Study in Physics (ISBN: 978-0199557684)
• Make Your Own Working Paper Clock (ISBN: 978-0060910662)

Writing Activity

Write an essay or a paragraph about whether you think a pendulum clock would work on the moon.

### Alignment to Curriculum Frameworks

Note: Lesson plans in this series are aligned to one or more of the following sets of standards:

#### National Science Education Standards Grades K-4 (ages 4-9)

CONTENT STANDARD A: Science as Inquiry

As a result of activities, all students should develop

• Abilities necessary to do scientific inquiry

CONTENT STANDARD B: Physical Science

As a result of the activities, all students should develop an understanding of

• Properties of objects and materials
• Position and motion of objects

CONTENT STANDARD E: Science and Technology

As a result of activities, all students should develop

• Abilities of technological design
• Understanding about science and technology

CONTENT STANDARD F: Science in Personal and Social Perspectives

As a result of activities, all students should develop understanding of

• Science and technology in local challenges

CONTENT STANDARD G: History and Nature of Science

As a result of activities, all students should develop understanding of

• Science as a human endeavor

#### National Science Education Standards Grades 5-8 (ages 10-14)

CONTENT STANDARD A: Science as Inquiry

As a result of activities, all students should develop

• Abilities necessary to do scientific inquiry

CONTENT STANDARD B: Physical Science

As a result of their activities, all students should develop an understanding of

• Properties and changes of properties in matter
• Motions and forces
• Transfer of energy

CONTENT STANDARD E: Science and Technology
As a result of activities in grades 5-8, all students should develop

• Abilities of technological design
• Understandings about science and technology

#### National Science Education Standards Grades 5-8 (ages 10-14)

CONTENT STANDARD F: Science in Personal and Social Perspectives

As a result of activities, all students should develop understanding of

• Science and technology in society

CONTENT STANDARD G: History and Nature of Science

As a result of activities, all students should develop understanding of

• History of science

#### National Science Education Standards Grades 9-12 (ages 14-18)

CONTENT STANDARD A: Science as Inquiry

As a result of activities, all students should develop

• Abilities necessary to do scientific inquiry

CONTENT STANDARD B: Physical Science

As a result of their activities, all students should develop understanding of

• Motions and forces
• Conservation of energy and increase in disorder
• Interactions of energy and matter

CONTENT STANDARD E: Science and Technology

As a result of activities, all students should develop

• Abilities of technological design
• Understandings about science and technology

CONTENT STANDARD F: Science in Personal and Social Perspectives

As a result of activities, all students should develop understanding of

• Personal and community health
• Science and technology in local, national, and global challenges

CONTENT STANDARD G: History and Nature of Science

As a result of activities, all students should develop understanding of

• Historical perspectives

#### Next Generation Science Standards Grades 2-5 (Ages 7-11)

Matter and its Interactions

Students who demonstrate understanding can:

• 2-PS1-2.  Analyze data obtained from testing different materials to determine which materials have the properties that are best suited for an intended purpose.

Motion and Stability: Forces and Interactions

Students who demonstrate understanding can:

• 3-PS2-1. Plan and conduct an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object.

#### Next Generation Science Standards Grades 2-5 (Ages 7-11)

Engineering Design

Students who demonstrate understanding can:

• 3-5-ETS1-1.Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.
• 3-5-ETS1-2.Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.
• 3-5-ETS1-3.Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.

#### Next Generation Science Standards Grades 6-8 (Ages 11-14)

Engineering Design

Students who demonstrate understanding can:

• MS-ETS1-1 Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.
• MS-ETS1-2 Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.

#### Standards for Technological Literacy – All Ages

The Nature of Technology

• Standard 1: Students will develop an understanding of the characteristics and scope of technology.
• Standard 3: Students will develop an understanding of the relationships among technologies and the connections between technology and other fields of study.

Technology and Society

• Standard 4: Students will develop an understanding of the cultural, social, economic, and political effects of technology.
• Standard 6: Students will develop an understanding of the role of society in the development and use of technology.
• Standard 7: Students will develop an understanding of the influence of technology on history.

Design

• Standard 8: Students will develop an understanding of the attributes of design.
• Standard 9: Students will develop an understanding of engineering design.
• Standard 10: Students will develop an understanding of the role of troubleshooting, research and development, invention and innovation, and experimentation in problem solving.

#### Standards for Technological Literacy – All Ages

Abilities for a Technological World

• Standard 11: Students will develop abilities to apply the design process.
• Standard 12: Students will develop abilities to use and maintain technological products and systems.
• Standard 13: Students will develop abilities to assess the impact of products and systems.

#### Student Worksheet

Build a Pendulum Clock

Research and Planning

You are part of a team of engineers who have been given the challenge of building a working clock based on a pendulum. You’ll need to be able to set the clock at two speeds, and will have to figure out how to adjust the materials you are using to make the clock run faster and slower. You’ll use every day items such as string attached to a rubber ball to serve as your pendulum. How you design your clock and what materials you use are up to you!

Read the handouts provided to you by your teacher, and if you also have access to the internet visit one of these sites to gain more understanding in the history and operations of pendulum clocks:

• A Walk Through Time (www.nist.gov/pml/general/time/)
• Clockworks — from Sundials to the Atomic Second (www.britannica.com/clockworks/startpage.html)

Parts of a Pendulum

A pendulum is relatively simple, and consists of only a few components: a length of string or wire, a bob or some type of weight, and a fixed point where it is attached to a solid object. Remember that a string may swing in various directions, but for the clock, you’d want to fix it to something, or use another material to keep the motion along a single plane — back and forth, not wobbling.

Design Phase

You have been provided with many materials from which to design and build your own pendulum clock. Remember that your clock doesn’t need to be perfect, but does need to be able to measure time fairly consistently. You can keep a chart or measurements of the “period of the pendulum” — which is the amount of time that it takes a pendulum to complete one full back-and-forth swing. Consider which materials you would like to use, and list them in the box below. On a separate piece of paper, draw a diagram of the clock you intend to build.

 Parts Required:

Measurement Phase

Measure the length of string you plan to use to attach your weight to in order to form a pendulum. You’ll need to keep track of this when you are adjusting the speed at which your pendulum moves. You may wish to weigh your pendulum weight as well to help you set your clock to work at two different speeds

Build it!  Test it!

Next build your clock and test it. You’ll need to be able to record time with your clock and set up your own scale or chart to keep track of the pendulum movements. Use a stop watch to see how many swings of the pendulum occur in 10 seconds. You’ll also need to speed up or slow down your clock.  (Hint:  adjusting the length of string attached to the pendulum might assist with this task.) You may share unused building materials with other teams — and trade materials too. Be sure to watch what other teams are doing and consider the aspects of different designs that might be an improvement on your team’s plan.

Reflection

Complete the reflection questions below:

1. How similar was your original design to the actual clock your team built?

1. If you found you needed to make changes during the construction phase, describe why your team decided to make revisions.

1. Was your clock able to measure time at two different speeds? What measurement scale did you devise to measure time with your clock?

1. Which clock that another team made was the most effective or interesting to you? Why?

1. Do you think that this activity was more rewarding to do as a team, or would you have preferred to work alone on it? Why?

1. If you could have used one additional material (tape, glue, wood sticks, foil — as examples) which would you choose and why?