Which type of lever is commonly represented by a wheelbarrow?

A wheelbarrow is a classic example of a second-class lever. In a second-class lever, the load is positioned between the effort (or force) applied and the fulcrum (the pivot point). In the case of a wheelbarrow, the wheel's axle acts as the fulcrum. When you lift the handles of the wheelbarrow, you apply force at one end (the handles) while the load—a heavy item in the wheelbarrow—sits in the middle.

This setup allows the user to lift heavier loads with less effort compared to a first-class or third-class lever. In a first-class lever, the fulcrum is positioned between the load and the effort, which often requires more exertion to lift a given load. Conversely, in a third-class lever, the effort is applied between the load and the fulcrum, which typically results in less mechanical advantage, making it harder to lift the same load.

Thus, the structure and functioning of a wheelbarrow clearly illustrate how it serves as a second-class lever, making the correct choice evident.