Which of the following is an example of a first-class lever?

The concept of a first-class lever revolves around the positioning of the fulcrum, the effort, and the load. In a first-class lever, the fulcrum is situated between the effort and the load, allowing for a change in direction of the applied force and enabling a mechanical advantage.

The use of a screwdriver to pry the lid off a can of paint illustrates this principle clearly. In this scenario, the fulcrum is the edge of the can where the screwdriver contacts it, the applied effort is where the user pushes down on the handle of the screwdriver, and the load is the lid of the can. By this configuration, the lever allows the user to lift the lid with a relatively small amount of force, making it an efficient tool for such tasks.

This design distinguishes it from other options, such as a wheelbarrow, which is classified as a second-class lever because the load is between the effort and the fulcrum, or a fishing rod, which operates more as a third-class lever. Understanding these classifications helps in visualizing mechanical advantages and understanding how tools and machines function based on the lever principles.