What is the formula for calculating the efficiency of a heat engine?

The magnitude of the poynting vector of a planar electromagnetic wave has an average value of 0.939 w/m^2 . the wave is incident upon a rectangular area, 1.5 m by 2.0 m, at right angles. how much total electromagnetic energy falls on the area during 1.0 minute?

Lake happy times contains 100 km3 of pure water. it is fed by a river at a rate of 50 km3/yr. at time zero, there is a factory on one shore of lake happy times that begins introducing a pollutant to the lake at a rate of 2km3/yr. there is another river that is fed by lake happy times at a rate that keeps the volume of lake happy times constant. this means that the rate of flow from lake happy times into the outlet river is 52km3/yr. in turn, the flow from this outlet river goes into another lake, lake sad times, at an equal rate. finally, there is an outlet river from lake sad times flowing at a rate that keeps the volume of lake sad times at a constant 100 km3 . (a) find the amount of pollutant in lake sad times at the end of 3 months. (b) at the end of 3 months, observers close the factory due to environmental concerns and no further pollu- tant enters lake happy times. how long will it take for the pollutant in lake sad times (found in part (a)) to be cut in half?

Sometimes questions that involve graphs will ask you to consider the effect of a changing factor or factors. problem​ statement: right arrow the line labeled d1 in the graph to the right shows the number of cups of lemonade that caroline and emily can sell at their lemonade stand at various prices. caroline and emily have noticed that they sell more lemonade when​ it's hotter. click anywhere on the graph to open a window with a control labeled temperature. if you use the slider to change the​ temperature, the line will shift. change the temperature from 80 degrees to 100 degrees. ​question: right arrow at a price of​ $0.50, how many more or fewer cups of lemonade do caroline and emily sell when the temperature is 100 degrees than when the temperature is 80​ degrees? ​(note: indicate the change in cups of lemonade​ sold: fewer will be a negative number and more will be a positive​ number)