One day when your friend from Problem 40 is picking up a package, you notice that he bends at the waist to pick it up rather than keeping his back straight and bending his knees. You suspect that the lower back pain he complains about is caused by the large force on his lower vertebrae ( in Fig. 8.32) when he lifts objects in this way. Suppose that when the spine is horizontal, the back muscles exert a force as in Fig. 8.32 (44 cm from the sacrum and at an angle of 12° to the horizontal). Assume that the cm of his upper body (including the arms) is at its geometric center, 38 cm from the sacrum. Find the horizontal component of when your friend is holding a 10-kg package at a distance of 76 cm from his sacrum. Compare this with the magnitude of found in Problem 40?

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