How Did They Do It? Objective To learn what levers are and how they might have been used by the ancient Egyptians in building their monuments. To learn what center of gravity is, how to determine the center of gravity of asymmetrical objects, and how this knowledge might have helped the Egyptians in building their monuments. Resources Summary for: Obelisk Mysteries of the Nile Dispatches Lever an Obelisk Obelisk Video Lever Loads Activity The Great Trilithon Balancing Act Activity Procedure To acquaint students with the construction challenge, have them review the summary for Obelisk. You may want to have students view the Obelisk video to further acquaint them with the challenges of raising a multi-ton obelisk. (The video can be purchased as part of the Secrets of Lost Empires set or individually. Allow a week for shipping.) Now familiarize students with the concept of levers. Print out the Lever Loads Activity and have students conduct both parts of the activity. Once it is available (Week of March 15) have students do the Lever an Obelisk online activity to further investigate the principle of levers. You may also want to familiarize students with the concept of center of gravity. You can print out and use The Great Trilithon Balancing Act Activity, which demonstrates how locate an object's center of gravity using a cardboard trilithon. As students are learning about these concepts, have them follow the expedition's progress by reading recent dispatches. Use these dispatches to discuss how the concepts students are learning are involved in the raising of the obelisk. (Note: Dispatches are expected to be posted every two days.) Have students develop a poster or model of how they would raise the obelisk. The poster should outline how each science concept comes into play at different points in the process. Students' concepts will differ depending on which method they choose to use. For example, if they use a pulley they might point out the concept of mechanical advantage or if they use a lever, they might point out fulcrum and load points. After performing the suggested activities, students should evaluate the suitability of using levers to move large masses of stone to build buildings or lift monuments such as obelisks. Would a lever have worked to lift the obelisk? What kind of lever? What might be some disadvantages to using a lever to raise the obelisk? For another version of this activity, check out Lever Loads Activity II. Standards Connections National Science Education Standards Grades 5-8 Content Standard E: Science and Technology Abilities of technological design Evaluate completed technological designs or products Students should use criteria relevant to the original purpose or need, consider a variety of factors that might affect acceptability and suitability for intended users or beneficiaries, and develop measures of quality with respect to such criteria and factors; they should also suggest improvements and, for their own products, try proposed modifications. This week on NOVA | Previous Sites | Lesson Ideas | Teacher's Exchange Editor's Picks | Previous Sites | Join Us/E-mail | TV/Web Schedule About NOVA | Teachers | Site Map | Shop | Jobs | Search | To print PBS Online | NOVA Online | WGBH © | Updated November 2000