Question

which of the following requires the action of a first class lever in the body?
a. jumping
b. push - ups
c. waving
d. nodding

please select the best answer from the choices provided.
a
b
c
d

Explanation:

A first - class lever has the fulcrum between the effort and the load. When nodding (moving the head up and down), the fulcrum is at the joint between the skull and the first vertebra (the atlanto - occipital joint). The muscles at the back of the neck provide the effort, and the weight of the head is the load. For jumping, push - ups, and waving, the lever systems involved are not first - class levers. In jumping, the lever system in the legs is more of a second - class lever (load between fulcrum and effort). In push - ups, the lever system in the arms is a second - class lever (the body weight is the load, the hands are the fulcrum, and the muscle effort is applied at the elbow). In waving, the lever system in the arm is a third - class lever (effort between fulcrum and load).

Answer:

D. nodding