(II) Energy may be stored by pumping water to a high reservoir when demand is low and then releasing it to drive turbines during peak demand. Suppose water is pumped to a lake 115 m above the turbines at a rate of 1.00 × 10° kg/s for 10.0 h at night. (a) How much energy (kWh) is needed to do this each night? (b) If all this energy is released during a 14-h day, at 75% efficiency, what is the average power output? (ID Water is stored in an artificial lake created by a lam

4. Suppose that a nuclear power plant has an efficiency of about 0.34, and generates 1000 MW of power. It is located on the banks of a major river that is 67 m wide near the plant, approximately 3 m deep, and flows at a rate of 0.5 m/s. Suppose that the plant re-routes all of this water into the plant and dumps its waste heat evenly throughout the water, then returns the warmer water to the river. How much warmer is the river downstream of the plant compared to upstream? Water's specific heat is approximately 4184 J/kg/K, and its density is 1000 kg/m³. [Answer: The water is warmer by 4.62 K. This is a lot warmer!]

A bathroom extractor fan being sold on Amazon has a duct diameter of 10.0 cm. It extracts air from a bathroom at a rate of 70.0 m3/h and the power supplied to the fan is 7.0 W. With what efficiency does the extractor convert electrical power into the kinetic power associated with the air-motion? Take the density of air to be 1.2 kg/m3 and assume laminar air flow.