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Secrets of Lost Empires II—Pharaoh's Obelisk

Classroom Activities

Objective
To discover how levers work by raising a brick with shish kebab skewers.

• copy of "Lever Lift" student handout (HTML)
• brick
• 2 bamboo shish kebab skewers
• small pebbles about the size of a quarter or half dollar (thin or flat stones work best)
• coffee can to hold small pebbles
• newspapers
• paper and drawing paper
• pencil and crayons

1. Review classes of levers with students. (See Activity Answer.) Remind students of the levers they saw in the videos. Provide each team with a copy of the "Lever Lift" student handout. Set up work area on newspapers. Go over the rules for erecting the brick. Require the scribe to use words and drawings to describe the team's work.

2. Stop the activity after a given amount of time. Measure the brick's height off the ground for each team. Discuss the processes used and difficulties faced.

3. Discuss with students what classes of levers they used and how they used them.

4. Have students present their work, explaining what did and did not work. Presentations might include drawings of the lever lift from different angles.

About Levers
Students will use levers in two of these four activities. They will use a Class 1 lever to raise the brick and a Class 2 lever to turn or move it. They will also use a Class 1 lever in designing their trebuchets.

If students are unfamiliar with classes of levers, run a mini-lesson with the following information:

When describing levers you need these four terms: lever, fulcrum, effort, and load. The lever itself is long and stiff. The fulcrum is the resisting point where the lever turns or pivots. Effort is the force you apply and load is what you move. When you apply effort, the lever pivots around the fulcrum moving the load.

The job the lever must do determines how the load, effort, and fulcrum are arranged. This arrangement determines the class of lever. Look at the following illustrations:

Once students understand the three different classes of levers, they will recognize them all around. Here's a quick method to classify levers.

1. Find the fulcrum. If it's in the middle, it's a Class 1. On the end, it's a Class 2 or 3.

2. To determine whether it's 2 or 3, find the load. If it's in the middle, it's a Class 2. On the end, it's a Class 3.

Ask students to identify the class of lever for the following:

• A claw hammer pulling a nail (Answer: Class 1. A hammer pivots on the middle of its head.)

• A wheel barrow (Answer: Class 2. The wheel is the fulcrum and the barrow is the load.)

• An oar rowing a boat (Answer: Class 1. The oarlock is the fulcrum.)

• A paddle paddling a canoe (Answer: Class 3. The top hand is the fulcrum and the blade is the load.)

• A bottle opener (Answer: Class 2. The fulcrum is on the end and the load is in the middle.)

Lever Lift
History records that Archimedes, an ancient mathematician and physicist, said, "Give me a lever long enough and a place to stand, and I will move the earth." His exaggeration proclaims the power of the simple lever. With levers, ancient Egyptians raised huge obelisks and the people of Rapa Nui raised massive moai. Because of their utility, levers became part of many other machines from trebuchets to modern devices.

This activity will help students understand the difficulties ancients faced in raising the obelisk or moai, including the instability of the rock pile and the problem of creating adequate fulcrums as the brick rises higher. For a follow-up exercise, students may want to raise a brick to the vertical. But as the ancients discovered, students will find that this will take many more stones and much more time.

Weighing In
Students may choose to find their own weight comparisons. To get them started, you may want to give them the following weights of some common objects: sport utility vehicle = 4,500 pounds (2,025 kilograms); blue whale = 150 tons (135 metric tonnes); bowling ball = 16 pounds (7.2 kilograms); refrigerator = 200 pounds (90 kilograms).

National Science Education Standards
Grades 5-8/9-12
Standard B: Physical Science—Motions and Forces