Final answer:
The question pertains to the forces exerted by the kneecap on the femur during knee extension facilitated by the quadriceps femoris muscle, with a consideration for the biomechanics of the knee joint and how gravitational potential energy changes during movement.
Step-by-step explanation:
The question is asking about the forces exerted by the kneecap on the upper leg bone (the femur) during knee extension, which is an action commonly associated with the quadriceps femoris muscle. The quadriceps femoris is a group of muscles located in the front of the thigh that are primarily responsible for extending the knee. According to the question, the quadriceps exert a force of 1250 N, and this force is transmitted via a tendon that runs over the kneecap.
In biomechanics, the interaction between the tendon, kneecap, and femur is significant because it influences how force is distributed during movements such as knee extensions. The patella serves to protect the tendon from the distal femur and to increase the mechanical advantage of the quadriceps. When the knee extends, it resists hyperextension and rotation, and a flexion movement in the sagittal plane takes place, decreasing the joint angle.
In terms of physics, when calculating gravitational potential energy (APEg) changes, such as during a fall, the equation KE = -APEg = -mgh is used, where 'm' is mass, 'g' is acceleration due to gravity, and 'h' is height. For smaller distances (such as the distance d the knees bend), the change in gravitational potential energy can usually be ignored if 'd' is significantly smaller than 'h'.