Which of the following is an example of a class 2 lever?

A class 2 lever is characterized by having the load positioned between the effort and the fulcrum. In this example, when standing on the balls of your feet, the toes act as the fulcrum, the body weight is the load, and the effort is applied at the calf muscles to lift the heels off the ground. This arrangement exemplifies the mechanics of a class 2 lever where the effort moves the load upward, with the fulcrum located at one end.

In contrast, the other scenarios do not follow the structure of a class 2 lever. For instance, a seesaw, which functions more like a class 1 lever, has the fulcrum in the middle, with the loads on either end. Nodding your head involves the motion of a class 1 lever as well, where the fulcrum is at the atlas vertebra, with the load being the weight of the head on one side and the neck muscles providing the effort on the opposite side. Similarly, elbow flexion is an example of a class 3 lever, where the effort is applied between the load (forearm) and the fulcrum (elbow joint). Cervical compression relates to axial loading rather than levers,