Which item serves as an example of a class 1 lever?

A class 1 lever is characterized by the placement of the fulcrum between the effort and the load. In the case of a crowbar, when used to lift a heavy object, the fulcrum is positioned at one end, with the effort applied on the opposite end and the load being lifted located in the middle. This configuration allows for a mechanical advantage, enabling the user to lift heavy objects with less effort.

Tweezers, wheelbarrows, and scissors do not fit the definition of a class 1 lever. Tweezers are more akin to a class 3 lever as the effort is applied closer to the fulcrum than the load. A wheelbarrow is a class 2 lever, where the load lies between the fulcrum and the effort. Scissors function as a pair of class 1 levers but are dependent on each half acting independently to cut, which complicates their classification as a single lever system. Hence, the crowbar is the best example as it clearly demonstrates the essential structure of a class 1 lever.