Designing Harmonic Timing Devices: Ready, Set, Escape

Engineers continually challenge themselves to make better and more accurate devices, tools, systems and processes, including timing devices. Typically, engineering projects also must consider design constraints, which are requirements and limitations unique to the challenge.

After this activity, students should be able to:

• Describe the steps of the engineering design process.
• Explain the concept of conservation of energy in relationship to kinetic and potential energy.
• Describe simple harmonic motion.

Your Engineering Design Challenge: You have been taken prisoner in a foreign country. You are going to try to escape from the prison. In order to escape, you must time the movements of the guards exactly! You have to design a method of timing three minutes, which is the time it takes the guards to change posts, so you can make your break.

You will be able to use a timing device to check the accuracy of the device. No clock/watch may be used in the device itself. You will be graded on how close you come to the three minutes. Good Luck!

Before the Activity

• Gather materials and make copies of the Pre-Activity Vocabulary Quiz (PDF)and Student Handout (PDF).
• Administer the quiz; glance at student answers.
• Divide the class into groups of four students each.
• Distribute the materials and handouts.

With the Students

Read aloud to the class the design challenge (the Introduction/Motivation section). Remind students of the steps of the engineering design process. Then have groups proceed with the activity, as described on the handout.

• In groups, brainstorm ideas to complete the task (record all ideas).
• Make a list of three materials you would like to bring from home (may not include any timing devices).
• Choose the best solution.
• Get approval from your teacher on additional materials being brought in.
• Explain why that solution was chosen.
• Sketch your solution.
• Build a prototype.
• Test the prototype (record time).
• Redesign to get a more accurate time.

Pre-Activity Assessment

Quiz: Before beginning the activity, administer the Pre-Activity Vocabulary Quiz (PDF) to gauge students' initial understanding of the vocabulary terms and concepts.

Activity Embedded Assessment

• Observe teamwork.
• Observe brainstorming and decision making processes.
• Note students' ability to observe and understand when the existence of kinetic and potential energy is in the system.
• See how students fill in the Student Handout (PDF) blanks and questions to gauge their depth of comprehension.
• Base the grades for the devices on how close to three minutes groups are able to measure time with the devices. Refer to the Example Grading Scale (PDF) for a suggestion on how to assign points.

Post-Activity Assessment

Homework Questions: Assign students to answer for homework the concluding questions at the end of the Student Handout (PDF). As a class, teview their answers the next day.

• When did your system have potential energy and when did it have kinetic energy?
• Were you able to observe conservation of energy in your system? If not, explain how it was conserved.
• Did your device follow simple harmonic motion? Explain.

• Do not permit use of candles or any type of open flame due to the fire hazard.
• Check that student designs do not include materials that might be safety hazards, such as falling objects, splashing water, etc.