In this experiment, we explore the wonderful world of simple machines, focusing on levers and how they work. Using some basic materials found around the home or classroom, students will construct a lever system and test several variables.

Levers belong to a class of objects called "simple machines" because they all have a minimal amount of moving parts. Other simple machines include the screw, the wheel and axle, the inclined plane, the pulley, and the wedge. The job of a machine, whether simple or complex, is to accomplish work more easily by somehow transforming energy or motion. To put it another way, machines help you get a job done with less effort.

The origin of the lever goes back to prehistoric times when people discovered that placing a rock under the end of a strong stick made it easier to lift heavy objects. All levers have two main parts: the arm, which does the actual movement, and the fulcrum, the point at which the lever pivots. In the case of this month's project, the pencil is the fulcrum. What we're working with this month is called a first class lever because the fulcrum is between the two ends of the arm. The end of the lever on which the force is applied is called the effort arm because this is where you must exert the effort. The end of the lever that does the lifting is called the load arm. By changing the position of the fulcrum, you can use a lever to lift a greater load without expending as much effort.

As with all simple machines, levers appear to give you "free energy" because your effort is reduced. However, as we all know, you don't get something for nothing. While it's true that moving the fulcrum closer to the load makes it easier to lift the load, you have to physically move the lever a greater distance. In this case, you're trading effort for distance. In the end, the amount of work you do is exactly the same.

The Dirtmeister's Science Lab on levers helps students meet the following science content standards as set forth by the National Research Council of the National Academy of Sciences:

• Students conduct a simple investigation. (A)
• Students employ simple equipment and tools to gather data and extend the senses. (A)
• Students use data to construct a reasonable explanation of how levers work. (A)
• Students communicate investigations and explanations. (A)
• Students discover that the position and motion of objects can be changed by pushing or pulling. The size of the change is related to the strength of the push or pull. (B)
• Technological solutions have intended benefits and unintended consequences. Some consequences can be predicted, others cannot. (E)
• Students learn that people continue inventing new ways of doing things, solving problems and getting work done. (F)

Classroom management is always a critical factor for any successful lesson, and the Dirtmeister's Science Lab is no exception. The following strategies will help to maximize the use of the activity in various classroom situations:

While younger students (grades 1 and 2) should have no problem manipulating the levers, they may have problems reading the rulers and quantifying the data. Instead of making actual measurements, they can trace the rulers and mark the balance point and the center of the ruler on a piece of paper. This way, they can graphically see how long the two ends of the rulers are.

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Extensions
Here are some suggestions to enhance the experience of Dirtmeister's Science Lab for your students:

Extensions on Levers

Grades K-2:

• Have the class make a list of all the levers that they encounter in the course of a week. What are some examples of the tools that use levers? Where do levers occur on the playground?
• Talk with your school librarian about available books and multimedia resources on levers and simple machines.

Grades 3-5:

• Have the class research levers that have been used in the past to solve problems in engineering. Were any ancient structures built with the help of levers? What did Archimedes have to say about them?
• For older students, work out the mathematics of levers. Use the formula for work (work = force x distance) and measurements of motion in a lever to prove that levers don't really give you "free energy."

General Extensions

Grades K-2:

• Provide space on a classroom bulletin board for the Dirtmeister's Science Lab. Assign different teams of students the task of designing the board and changing the postings to reflect the different Science Lab topics throughout the year.

Grades 3-5:

• Using computer software such as ClarisWorks(TM) or Microsoft Works(TM), have students create and maintain electronic science journals. Encourage students to illustrate their work by using drawing or painting features of the software. This is an excellent way of keeping notes and storing the labs for future use.
• Have each student write an article about their favorite science experiment. Compile the articles into a science newsletter. If your class already publishes a monthly newsletter, feature a science topic in each issue, rotating the responsibility of writing the articles throughout the class.

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Resources
The following Scholastic supplemental materials can be used in conjunction with Dirtmeister's Science Lab.

• Big Books: Science (Grades K-4). This book series covers a variety of topics, from bugs to wind. They are brightly illustrated and great for the classroom library.

• Environmental Atlas of the United States, by Mark Mattson (Grade Levels 4 and up). The only environmental atlas for young readers that emphasizes U.S. ecological information.

• Be a Scientist skills books (Grades 3-6). This series includes featured scientists, hands-on activities, and an emphasis on practical process skills. The series consists of three sets of three books each for grades 3-4, 4-5, and 5-6.

• Super Science (Grades 3-6). High-interest articles and hands-on activities teach basic science and technology concepts. Each theme-based issue presents timely news and stimulates students' interest through fun activities. Exercises develop critical-thinking skills and help you meet the Natural Science Education Standards.

• Quick and Easy Learning Centers: Science, by Lynne Kepler (Grades 1-3). This Professional Resource book focuses on the use of everyday materials to promote independent, hands-on learning. Information on how-tos, management, experiments, and reproducibles are included in this helpful book.

Call Scholastic directly at 1-800-724-6527 to order and for more information.

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Related Web Sites

Simple Machines

Lego Dacta Enrichment Project: Gander Academy
A site created by the Centre for Innovative Technology Education provides eight activities for using Lego Dacta equipment in the classroom to focus on gears and pulleys. Lesson plans and student worksheets are provided.
http://www.stemnet.nf.ca/CITE/

General Science Sites

Science and Technology for Children Curriculum
http://www.si.edu/nsrc/pubs/stc/overv.htm

Caroline Arnold
http://www.geocities.com/Athens/1264/

The Natural History Museum
http://www.nhm.ac.uk/index.html

Edison National Historic Site
http://www.nps.gov/edis/

Endangered Species Program
http://endangered.fws.gov/

National Inventors Hall of Fame
http://www.invent.org/hall_of_fame/1_0_0_hall_of_fame.asp

Understanding Our Planet Through Chemistry
http://minerals.cr.usgs.gov/gips/aii-home.htm

Maps and References
http://www.cgrer.uiowa.edu/servers/servers_references.html

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