What is a common example of a first-class lever?

A common example of a first-class lever is a seesaw. In a first-class lever, the fulcrum is positioned between the effort and the load. This setup allows the user to lift a load with less effort by applying a force on one side of the lever while the load is placed on the opposite side.

In the case of a seesaw, the board rests on a central pivot point (the fulcrum), and when one end is pushed down, the other end rises, demonstrating the principle of leverage. This design allows for the efficient transfer of energy and can make lifting heavy objects easier, depending on where the load is placed relative to the fulcrum.

Other options represent different classes of levers: a wheelbarrow exemplifies a second-class lever because the load is between the effort (where the handle is lifted) and the fulcrum (the wheel), while a pair of scissors is a moving example of a second-class lever as well, with the fulcrum at the pivot, and the effort applied at the handles. A crowbar is typically a class two lever due to the effort applied farthest from the fulcrum, allowing it to lift heavy objects.