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 Secrets of Lost Empires I—Inca Classroom Activity

Objective
To construct suspension cables out of newspaper.

• copy of "Hang in There!" student handout (PDF or HTML)
• newspaper
• four paper clips
• paper cup
• scissors
• tape
• stapler
• weights (such as washers, coins, books)
• various pieces of string, yarn, thread, twine, or rope
• hole puncher
• two chairs
• sheet of paper
1. Students can try constructing suspension cables out of strips of newspaper in this activity.

2. Organize students into small groups and distribute copies of the "Hang in There!" student handout and a set of materials to each group.

3. Encourage students to look at the weave in samples of thread, string, yarn, and rope as they investigate ways to increase the weight-bearing strength of newspaper strips.

4. Provide students with weights or washers to test simple cables. As the amount of weight the cables can sustain increases, students can suspend heavier objects, such as books. When twisting or braiding strips, students might want to staple or tape the ends together. Ask students how the staples or tape might affect the strength of the newspaper and have them think of ways to combine newspaper strips without these materials.

5. As an extension of this activity, challenge students to create a strong cable using a limited amount of newspaper. Give each team the same amount of newspaper (such as the front section) and have them create a cable that spans 2 m (6.5 ft) and supports the most weight. Ask each team to describe the method it used and why. Which method(s) sustained the most weight and used the materials most efficiently? Discuss how sometimes there is no one best design and how many different designs can meet the challenge.

Students' cable designs will vary. They will find that multiple strips of newspaper are able to support more weight than a single strip. They should also notice that many different methods support the same amount of weight. Students can evaluate methods using criteria such as the most efficient use of material, the most easily constructed method, or the method that supports the greatest amount of weight.

Ask students if they've ever crossed a suspension bridge. There are a number of suspension bridges in the United States, including the George Washington Bridge in New York City. This bridge spans 1.1 km (3,600 ft) and is supported by four main cables. Each cable is 1.6 km (1 mi) long and contains 26,000 strands of steel. If all of the strands that make up the cables were laid end to end, they would circle the earth four times.

 Secrets of Lost Empires I—Inca Original broadcast:February 11, 1997

 Grass Bridge Watch in this Teachers' Domain video segment (4m 50s) residents of the Peruvian Andes as they build a traditional and functioning grass bridge.