Lesson 2.2: Exploring Conservation of Energy
Unit: Work and Energy, Component 2 – Conservation of Energy
Date: January 10th, 2013
Day/Block: Day 1 – A/E/F
Time Available: A 58min / E 48min / F 65min
You will be able to design and analyze a Rube Goldberg Machine using the Law of Conservation of Energy.
Criteria for Success:
Can I design my own machine that transfers mechanical energy between objects through work?
Can I use the Law of Conservation of Energy to explain how my design transfers energy?
Handout with machine design and analysis questions.
[10 min] DoNow:
The complicated chain of events in the music video is called a “Rube Goldberg Machine”. These machines use many transfers of energy between a whole lot of objects in order to do a very simple task.
Invent your own small (2 objects) Rube Goldberg machine. How would you use one object to make another object do something else? Where is there work and energy? How does one object transfer energy to another?
[10 min] Discussion: Music Video
Show OK Go’s music video for “This Too Shall Pass”: (4 min)
Note: Watching the video was assigned as homework the previous night, along with the following guided questions: Where do you see work? Where do you see energy being transferred from one form to another? Write down at least 1 example (note the video time), and make sure to explain what object is doing work on what other object, what kind of energy is being transferred, and how you know.
Talk to a partner next to you and share 1 example of work and energy being transferred from one object to another. I will ask several students to share an observation that their partner noticed, and explain to me what object is having work done on it and what kinds of energy are involved.
Possible questions to ask:
What did you see? Be specific, tell me what happened to the object that makes you think there was work done. What kinds of energy do you think that the object has? How do you know that the object has that kind of energy?
Record student observations on the whiteboard.
[15 min] In-Depth Analysis: Tire
Show video clip of the tire section twice (7 second clip starting at 1:03). Ask students to write down exactly what they see happening to the tire. Have students share their observations, and assemble a record of the tire’s journey on the board to refer to later. (Make sure that the bucket hitting the tire is included.) Hand out the worksheet for scaffolded analysis of the tire scenario.
Refer to your handout. Take 30 seconds to answer the first question by yourself. Ask one student to share what they wrote with the class.
1. At the beginning of the scenario, does the tire already have mechanical energy? If so, what form(s) is it in, and how do you know?
Take two minutes to answer questions 2 and 3 with a partner. Ask one or two pairs to share, depending on time.
2. During the scenario, is work done on the tire by any other object? Is this work positive or negative, and how do you know?
3. What happens to the tire’s total mechanical energy when the work is done to it?
Take four minutes to answer questions 4 and 5 with a partner. Ask one or two pairs to share, depending on time.
4. Describe what happens to the tire’s GPE, KE, and total ME as it goes through the scenario.
5. What happens to the tire’s mechanical energy at the end of the scenario?
[15 min] Creative Activity: Design and Analyze
Turn over your handout. Now you have a chance to design your own Rube Goldberg machine! Draw your machine in the space provided, and use the Tire Analysis as a guide to answer the analysis questions below. The questions are due tomorrow for stamps. If you don’t finish in class, please complete the analysis questions as homework.
6. Draw your own piece of this Rube Goldberg Machine that uses 1 object. You must include at least 1 transfer of energy from one object to another.
7. What is your main object in this scenario? :
8. Describe what happens to your object’s GPE, KE, and total ME as it goes through the scenario beginning to end..
9. Where is work done on your object or by your object? How does this work change your object’s total mechanical energy?
10. Explain how your machine obeys the Law of Conservation of Energy, MEi + W = MEf.