(a) Calculate the gravitational potential energy stored in the pyramid, given its center of mass is at one-fourth its height. (The pyramid’s dimensions are slightly different today due to quarrying and some sagging.) Historians estimate that 20,000 workers spent 20 years to construct it, working 12-hour days, 330 days per year. Its square base, originally 230 m on a side, covered 13.1 acres, and it was 146 m high, with a mass of about 7 × 10 9 kg 7 × 10 9 kg. The awe-inspiring Great Pyramid of Cheops was built more than 4500 years ago. 05 × 10 20 J ) ? size 12 (These energy consumption values are from 2006.) (This small conversion efficiency is due to the devices themselves, and the fact that the sun is directly overhead only briefly.) With the same assumptions, what area would be needed to meet the United States’ energy needs ( 1. Calculate the area in km 2 km 2 of solar energy collectors needed to replace an electric power plant that generates 750 MW if the collectors convert an average of 2.00% of the maximum power into electricity. ) (b) Part of this is absorbed and reflected by the atmosphere, so that a maximum of 1.

(Take the power output of the Sun to be 4. (a) Calculate the power per square meter reaching Earth’s upper atmosphere from the Sun.

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