A woman who is late in her pregnancy often leans backwards slightly when getting out of chairs and even while walking.

(a) Using the concept of torque, explain why she does this. Standing and walking (while in the family way) often causes lower back pain. But when she wears a backpack this pain is reduced or even eliminated.

(b) Why is the backpack helpful

(c) Is there an optimum pack weight for minimal discomfort?