E problem-setd-2022fa (2).pdf 5i (6pts) A person holds a box with a mass of 25 kg in two positions relative to the sacroiliac joint (Slin image below). In the position with the arms more extended, the center of mass of the box is 55 cm (0.55 m) from the 81 joint, while in the position with the arms more exed, the center of mass of the box is 30 cm (0.30 In) from the 51 joint. If the back extensor muscles operate with a moment arm of 4.7 cm (0.047 in) relative to the SI joint, how much force do the back extensor muscles need to generate while holding the box statically in these two positions? If we assume the individual weights 81 kgs and the combined center of mass of the head, arms and trunk are directly over the S1 and make up 68% of that person's total weight, how much force is there on the 51 joint in both positions. Draw the FBD (use a generic 'nm' for the box so that you only need to draw 1 FBD that represents both scenarios). Torque produced by the box about the 51 joint Extended arm position: Flexed arm position: Back extensor muscle force Extended aim position: Flexed arm position: W Extended arm position: Flexed arm position: DRAW FBD