Welcome to Easter Island..

Background

• Lever LiftHistory 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 you 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.

Rules• Secrets of Lost Empires: Pharaoh's Obelisk & Easter Island • Student Handout • Lever Lift• A Great Ruler has selected your team to erect a brick obelisk. How

will your team raise it? Because a brick is tiny compared to a real Easter Island head, you must work under the following conditions to begin to experience the difficulties the ancients faced:

• You may not touch the brick with your hands.• You are limited to 2 bamboo shish kebab skewers for your levers.• You must use the small pebbles for support stones.• A team member or members must act as scribe to draw and record

what class of levers you used, what difficulties you had, and how you overcame them.

I. Objective

• To calculate the force needed to lift an object with a lever and the mechanical advantage of a lever.

II. Hypothesis

If I calculate the ______________ of an object and measure the ________(s) the object is raised and the lever travels, then I can calculate the ____________ needed by the lever.

III. Procedure

• Gather materials– 1 brick– 2 shish kebobs– 1 bin of small stones– cm ruler

• Use shish kebobs and small stones to create levers (either class 1,2,or 3)

• As you raise the brick, slide small stones under the brick to keep it from falling.

• Raise the brick as high as you can in the time allowed.

III. Procedure

• Analyze three of your lever steps– First determine if you have constructed a class 1,2, or

3 lever and why (check lever slide to verify) – Illustrate your levers, label fulcrum, effort, and load. – Measure the height the brick raises and the distance

the lever arm travels in cm. Convert to meters. record– The bricks mass is 2.7 kg, calculate the force (weight)

of the object due to gravity. F=ma– Now calculate the force needed by each of the three

levers. • remember: (Force of brick)(distance of brick)=(force of lever)

(distance of lever) Because the force of the brick in BIG and the distance you can make it travel is small, then the distance the lever travels is BIG and the force is small.

III. Procedure

• Fd=fD• Solve for

f• f=Fd D• Repeat

for two more levers

F=Force of brick (N)

d=distance of brick (m)

f=force of lever (N)

D=distance of lever (m)

Now calculate the Mechanical Advantage (MA) that the lever gives you by comparing how many times greater the force of the brick is compared to the lever.

IV. DATA

F, Force of Brick (ma)

d, Distance brick lifts

D, distance of lever

f, force of lever

(f=Fd/D)

Lever 1

Lever 2

Lever 3

V. Analysis

1. Calculate the MA (Mechanical advantage) of each lever.

2. If you used a lever with the same mechanical advantage, what force would you need to supply to lift one of the Easter Island heads? Easter Island heads weighs 12700kg.

VI. Conclusion

• Did you support or reject your hypothesis?• How much of a mechanical advantage did the

lever give you?• By comparing the small scale Easter Island head

system to the mass of the actual artifacts give you an understanding of how important levers are as tools? Is it practical to believe that humans accomplished these great tasks with only simple tools?

• What error may have occured in your lab, what changes would you have made to the lab to reduce error?