The decay of 40K has a half of 1.3 × 10 9 years. The age of the earth is estimated at 4.6 × 10 9 years. The decay of 40K is a major heat source for the earth's interior. Relative to today, how much more heat was produced by 40K in the early Archaeon era or 3.9 × 10 9 years ago?

Panel bc in fig. p2.76 is semi-circular, with the 3 meter radius and horizontal straight edge through point b. compute (a) the hydrostatic force of the water on the panel, (b) its center of pressure, and (c) the moment of this force about point b. assume atmospheric pressure on the dry side of the panel