Which feature signifies to astronomers that a distant star is part of a planetary system? A. The star periodically dims. B. The star expands into a red giant. C. The star moves through the sky. D. The star continuously gets brighter.

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?

Around faucet handle is part of a(n) a. lever b. screw c. inclined plane d. wheel and axle

Which radioisotope is used in dating geological formations?