20. A bullet is fired vertically upward from a gun and reaches a height of 7000 ft. (a) Find its initial velocity. (b) How long does it take to reach its maximum height?
(c) How long is it in flight?

Acoal-fired plant generates 600 mw of electric power. the plant uses 4.8 x 10^6 kg of coal each day, and the heat of combustion of coal is 3.3x 10^7 j/kg. the steam that drives the turbines is at a temperature of 300° c, and the exhaust water is at 37° c. (a) what is the overall efficiency of the plant for generating electric power? (b) how much thermal energy is exhausted each day? (c) what is the change in entropy of the universe for this heat engine? (d) using the same heat reservoirs, what is the maximum possible (carnot) efficiency for a heat engine?

The movement of electrons between atoms is called an

2) the sun is wonderful source of energy. it is renewable and natural with few dangers. solar cells rely on the sun for energy. these cells would be more practical to use if they were