Begin the Investigation by reviewing with the class the concepts they explored while using the lever in Investigation Four.

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Use the following questions to help students apply their Recall tool as they review the concepts involved with the operation of a lever.

Ask students: What is a lever? A simple machine that uses a beam that turns on a fixed point, called the fulcrum.

How does changing the position of the fulcrum of a lever change the force exerted to lift the load? As the fulcrum is moved further from the load, the amount of force required to move the load increases. As the fulcrum moves closer to the load, the force required to lift the load decreases.

How does changing where the force is applied on the effort arm of the lever affect the force needed to lift the lever? As effort along the effort arm is moved closer to the fulcrum, the length of the effort arm decreases. As the length of the effort arm decreases, the force needed to lift the load increases.

Does a lever reduce the amount of work you do to lift a load? Why or why not? No. The amount of work done is the same whether the load is lifted with or without the lever. A lever is a simple machine. Simple machines do not change the amount of work done when performing a task, they simply make work feel easier. In the case of the lever, the force needed to lift a load is decreased by increasing the distance over which the force is applied. This occurs when the fulcrum moves closer to the load arm or the length of the effort arm increases. This reduction in force can make the work seem easier. A lever can also decrease the distance over which the force is applied by increasing the force required to lift the load. This occurs when the fulcrum moves further from the load or the length of the effort arm decreases. The reduction in the distance the load is lifted may also make work feel easier.

What is the advantage of using a simple machine like the lever? Simple machines make work feel easier by increasing the distance over which the force is applied thereby decreasing the force, or increasing the magnitude of the force in order to decrease the distance over which the force must be applied.

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Transition students into associating the concepts of force and work to the use of another simple machine, the inclined plane. Introduce the inclined plane to students. Ask students to refer to their Scientist’s Glossary during the discussion. Utilize the steps and questions that follow to encourage class discussion:

• Draw students’ attention to the drawing on this slide that represents an inclined plane.

Ask students: How would you define an inclined plane? A simple machine that has a flat surface that connects a low point to a high point. It has a certain height and length.

Ask students: Can you think of any examples of where you may have seen an inclined plane? Student answers will vary. Examples could include access ramps into buildings and sliding boards on a playground and roller coasters.

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Ask students: What are some similarities and differences between the three inclined planes shown in the slide? Student answers will vary. There are differences in the height and length of the inclined planes. The height and length of all of the inclined planes are not the same. The height of the inclined planes A and C is the same but the length is different. The length of inclined planes A and B is the same but the height is different. Students may also suggest that the steepness of the inclined planes differs.

Ask students: Look at the steepness of each inclined plane. How would you compare the steepness of incline planes A, B, and C? Is there one that is steeper than the other? Students should indicate that the steepness or angle (degree) of the inclined plane is not the same for inclined planes A, B, and C. Inclined plane A is steeper than incline planes B or C. Students may suggest that inclined planes B and C have the same steepness or angle (degree) of incline.

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• Think about the terms effort and load. Based on the descriptions in your Scientist’s Glossary and your experiments with the pulley and lever, where do you think the load would be placed and the effort applied on an inclined plane?
• Students may experience some difficulty in locating the placement of the load and effort on the inclined plane because the operation of the inclined plane is different from that of the pulley and lever.
• Explain to students that the placement of the load and effort on an inclined plane is different than the pulley and lever. Use the diagram of the inclined plane as a visual aid during the discussion. 
• As with the pulley and lever, effort is the force applied in order to move an object. On an inclined plane, if a person pushed or pulled a box up the plane’s surface, the effort would be the force of a person’s push or pull. The load is the object that is pushed or pulled along the inclined plane.

Ask students: Where is the effort applied? The effort is applied to the load in order to pull or push the load up the inclined plane.

Ask student: What is the load? The load is the object that is moved up the inclined plane.

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• Tell students that they will conduct experiments in Investigation Five using different inclined planes. As they conduct their experiments they should think about whether an inclined plane changes the amount of effort needed to lift a load. 

• Students should also think about whether differences in the steepness of the inclined plane will change the amount of effort applied to move a load and the amount of work done to lift a load.