For Exercises 16–20, refer to the following. Energy can be thought of as power applied over time. Power can be measured in kilowatts and energy in kilowatt-hours (kWh), where 1 kilowatt-hour is 1000 watts of power exerted for 1 hour. For example, a 40-watt bulb burning for 24 hours consumes 960 watt-hours ≈ 1 kWh. Other forms of energy, such as food or gasoline, can be converted to an equivalent in kWh.
17. The Toyota Prius recovers energy to its battery when the car brakes. In the “classic” Prius model (2002-2003), for each 50 watt-hours (Wh) of energy recovered, an icon appears on the dashboard screen. A gallon of gasoline contains 33.7 kWh of energy. Suppose gasoline costs $3.00/gal. How many icons would have to appear before the car saves $1 in gasoline cost? (We neglect consideration of the relative efficiency of the car in converting gasoline or recovered electrical energy into mechanical motion.)
17.
225 (So it’s mainly a “feel-good” icon.)