Simple machines are mechanical devices that are used to make work easier. Combinations of two or more simple machines working together are called compound machines. These machines create systems for different kinds of movement to occur when force is applied to a load. Both simple and compound machines make work easier by changing the size or direction of the force.
A LEVER is a simple machine made of a rigid beam and a fulcrum. The effort (input force) and load (output force) are applied to either end of the beam. The fulcrum is the point on which the beam pivots. When an effort is applied to one end of the lever, a load is applied at the other end of the lever. This will move a mass upward.
Levers are very useful simple machines used for transferring force. You may not realize it, but you use levers every day!
There are three types, or classes of levers:
1. In a first class lever, the fulcrum is located between the load and the effort.
If the fulcrum is closer to the load, then less effort is needed to move the load a shorter distance. If the fulcrum is closer to the effort, then more effort is needed to move the load a greater distance. A teeter-totter, a car jack, and a crowbar are all examples of first class levers. First class levers are very useful for lifting large loads with little effort.
2. In a second class lever, the load is located between the effort and the fulcrum.
If the load is closer to the fulcrum than the effort, then less effort will be required to move the load. If the load is closer to the effort than the fulcrum, then more effort will be required to move the load. A wheelbarrow, a bottle opener, and an oar are examples of second class levers.
3. In a third class lever, the effort is located between the load and the fulcrum.
If the fulcrum is closer to the load, then less effort is needed to move the load. If the fulcrum is closer to the effort, then the load will move a greater distance. A pair of tweezers, swinging a baseball bat or using your arm to lift something are examples of third class levers. These levers are useful for making precise movements.
