How to Make a Fulcrum Model for Science Class

The teeter-totter is a classic example of a Class 1 Lever.

The six simple machines are a focus of many a middle school science unit. With the inclined plane, wheel and axle, screw, lever, pulley and wedge, humanity has created some amazing things. The fulcrum is a key piece of one of these simple machines, the lever. The lever itself comes in three different types, or classes, depending on the relationship between the lever itself, the load, the effort and the fulcrum, or pivot. A fulcrum model helps demonstrate the uses of the different classes of levers, which you probably use in your daily life without realizing it.

Things You'll Need

• Ruler or long stiff piece of board
• Brick, cinder block or whatever will work as a fulcrum for your lever's board
• Object for the load

Instructions

1. Begin building any lever by placing the brick, cinder block or whatever you are using as the fulcrum in position. Make sure that it is stable, anchored and will not move, otherwise you will lose efficiency of your lever, and possibly incur damage.

2. To construct a Class 1 Lever, place the board that will function as the lever approximately centered on the fulcrum, or pivot, that you placed in Step 1. Place the load on the far end, and then apply effort on your end of the lever. You apply effort in the direction opposite that which you desire the load to go, in about equal force required to move the object.

3. 

   A wheelbarrow employs a traditional Class 2 Lever.

   To adapt your fulcrum model to create a Class 2 Lever, place the board so that it ends on your fulcrum, and place the load in the middle of the board. In this model, the effort is applied in the same direction that you desire the load to move. The simple machine Class 2 Lever in this case makes it such that more work must be done (you must pull further on the lever than you intend the load to move), but that work is easier (the object feels lighter).

4. 

   A fishing pole is a Class 3 Lever; your body is the fulcrum, and your arm provides the effort to move the load, or the fish on the far end.

   Using Class 3 Levers is more rare. To turn your fulcrum model into a demonstration of such a lever, leave the fulcrum and board in the same position as for Class 2, but move the load to the far edge, where you had been applying effort. Now the effort is applied in the middle, and you will raise the load a greater distance than you apply as effort. This machine's benefit is that the work is harder, but there is less of it to do.

References

• Glenn Learning Technologies: Resource Chart
• Enchanted Learning: Levers