- If a population grows at the rate of 2% per year, in how many years will it approximately double?
- A big coal digger is moving an average of 23 tons of subbituminous Wyoming coal per minute into dump trucks. This coal has an energy content of 10,750 Btu/lb. How many gigawatts (GW) of power does this flow of coal represent?
- Suppose 2 large tankers containing liquefied natural gas (LNG) leave a gas export terminal every day. The methane is stored in liquid form in the tankers, at -260°F, in a volume 600 times smaller than would be needed in gas form, at STP (Standard Temperature and Pressure: 0°C temperature, 1 atm pressure). Suppose the average tanker at this port carries an amount of LNG equivalent to 118 million cubic meters of methane at STP. The energy content of methane is 38.5 MJ per cubic meter at STP. How many gigawatts (GW) of power does this daily flow of natural gas through the port represent?
- Consider a heat engine that has an exhaust temperature of 227 degrees Celsius. If the Carnot efficiency for this engine is 34%, what is its high temperature (in degrees Celsius)?
- Suppose a region has been sprinkled with Cs-137 by a nuclear accident, and the radiation from the soil from Cs-137 is 581 times the normal background radiation. After waiting for 120.7 years, what would be the ratio of this Cs-137 radiation to the normal background radiation? The half-life of Cs-137 is 30.17 years.
- Suppose a bicyclist is burning 49 Calories per mile traveled. Convert this rate of energy use to a number of “miles per gallon of gasoline equivalent,” by comparing this to the caloric content of one U.S. gallon of gasoline (132 MJ). (This is similar to the number of miles per gallon of, e.g., olive oil, because gasoline and vegetable oils have similar mass density (~0.72 g/cc vs. ~0.9 g/cc) and caloric density (~11.6 Cal/g vs. ~9 Cal/g).)
Sample Solution
