Examples of common household levers include scissors, pliers, a hammer's claw, a stapler, a bottle opener, nail clippers, a fishing rod, tweezers and tongs. Other examples of household levers include a seesaw, crowbar and a balance scale. A lever is a simple machine that involves moving a load using a pivot motion as a force.
Levers are divided into three classes depending upon where the force is located. A first-class lever is where the pivot point (fulcrum) is between the weight being moved and the force moving the weight. First-class levers includes a seesaw, crowbar and pliers. A second-class lever is a stick where the fulcrum is at one end and the weight is in the middle. Examples of such simple machines include a wheelbarrow, door, stapler and can opener. A third-class lever involves the fulcrum at one end of the stick, the weight on the other and the force is in the middle. Third-class levers include a broom, hoe, fishing rod, baseball bat and human arms.
Levers were first identified as simple machines by Archimedes around 260 B.C. Animals such as orangutans and otters use levers to eat their food, and humans have used levers as tools for roughly 200,000 years.