What causes water pipes to break in freezing weather

Let f(x) = x4- 8x2 . find the relativeextrema of this function using the second derivative test.

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?

Assume this car is driven off a cliff . how many arrows of force need to be drawn in the free body diagram? assume no air resistance -five -one -three -four