What is meant by radioactivity?

high-energy subatomic particles
disintegration of the nucleus
unstable atoms
all of the above

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?

Which situation will have the highest resistance? a.long wire and high temperatureb.short wire and high temperaturec.long wire and cold temperaturedshort wire and low temperature

In what direction does an applied force move an object