hefbomen

Hefbomen, or levers, are rigid bars that rotate about a pivot, called the fulcrum. They are one of the oldest and most fundamental simple machines, enabling people to lift or move heavy loads with a smaller input force.

A lever works by producing torque around the fulcrum. The product of the input force and its distance from the fulcrum (the effort arm) equals the product of the output force and its distance from the fulcrum (the load arm) when the system is balanced. The mechanical advantage is the ratio of the effort arm to the load arm, or equivalently the load force divided by the input force.

There are three classic classes of levers: first-class levers have the fulcrum between effort and load (examples: seesaw, crowbar); second-class levers have the load between the fulcrum and the effort (wheelbarrow, nutcracker); third-class levers have the effort between the fulcrum and the load (tweezers, human forearm when lifting a dumbbell). Each class provides a different balance of force amplification and speed.

History and use: The concept was formalized by Archimedes, who noted that a small force could move a heavy object given a sufficient lever arm. Levers are used in many devices, from door handles and pliers to scales and balancing mechanisms, and they underpin many engineering systems that convert force and movement.

In analysis, levers illustrate torque and mechanical advantage, and they interact with friction and elasticity in real-world applications. While simple, the lever remains foundational in physics and engineering education, and it forms the basis for more complex machines that combine multiple levers.