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Lever Loads Activity adaptation
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The Lever Loads Activity has students follow directions to devise a lever and then think about some of the aspects related to levers. This adaptation adds a level of complexity by having the students complete a challenge:

Materials for each group

one spring scale
two textbooks or notebooks
one wide, flat board, about 3 or 4 feet long, prepared with thumbtacks and hook as described below.

Board preparation

The board should have 3 pairs of thumbtacks (the kind with the large, plastic, brightly colored handles) inserted into it on one end; one pair very near the end, one pair about 1 foot from the same end of the board, and the last pair a second foot from the same end of the board. These pairs of thumbtacks are to act as braces to keep the "load" (a textbook or notebook) from sliding off the end of the board. Having three pairs of the braces allows the students to try putting the load in three different locations on the board, to test how moving the load closer to the fulcrum affects how much force is needed to lift the load. The board should have a screw hook inserted into end opposite from the thumbtacks. This will serve to hook up the spring scale.

        Board--> _T________T_________T_______________________________H

T = Pair of thumbtacks
H = Hook to attach spring scale

Procedure

Introduce the concept of a lever with something like this: "This is a lever. It's just like a seesaw on the playground. As you apply a force downwards on one end, the other end lifts a load. Between the two ends is the fulcrum; the point over which the lever swings."
Then the students could be given some materials and a challenge: Use the given materials to lift the load with the least amount of force. Do this by varying the placement of the load, the force, or the fulcrum. Draw your solution on a piece of paper and label the three parts of the lever. Draw every solution which you try, whether or not it works.
While one student holds the fulcrum (an upright book or notebook) in place, the board is placed over the fulcrum, and a second book or notebook is placed on the end of the board with the thumbtacks. The spring scale is attached to the hook, and a different student begins to pull down on the spring scale, which should begin the lift the load on the opposite end of the board. The student can then read what the spring scale says, and the two students can try different configurations of the lever, until they are certain they have found the way to lift the load with the least amount of force. Doing this should drive them to the conclusion that the easiest way to lift a load is to put the fulcrum as close as possible to the load.
The next challenge to the students would be to find the way to move the load the greatest amount of distance, using the same materials. Have students keep track of each setup tested and how much force registered on the spring scale for each setup. When they finish, they should have concluded that the way to move the load the most is to keep the fulcrum closer to the force acting on the lever.
When they are finished, have a class discussion about the advantages and disadvantages of each setup—one is good for lifting heavy loads a short distance; the other can move objects a long distance but requires much more force.

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