Lifting the lid of a can of paint (with a screwdriver, or other similar solid rod) is an example of a first class lever. Levers are one of the simple machine types known since ancient times.
Levers are defined as first, second, or third class depending on where the fulcrum (the pivot point around which the lever operates) is in relation to the load (the thing we are trying to move) and the effort (where we exert force on the lever). Lifting a paint can lid uses a first class lever because the lid being lifted (the load) is at one end of the lever, the fulcrum (in this case the edge of the paint can) is in the middle) and the force (a person pushing down on the screwdriver outside of the paint can) is at the other end. A seesaw is another example of a first class lever.
Second class levers have the fulcrum at one end, and the effort at the other, with the load in between. Wheelbarrows and staplers are examples.
Third class levers have the fulcrum at one end, the load at the other, and the effort in between. An example for this type is use of a fishing pole.
See the link below for diagrams that will help you to understand the differences.
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