Work can be negative as well as positive because an object or system can do work on its surroundings as well as have work done on it. Which of the following statements describes: a situation in which an object does work on its surroundings by decreasing its velocity and
a situation in which an object can do work on its surroundings by decreasing its altitude?
Choices:
a). A gasoline engine burns less fuel at a slower speed. 2. Solar cells capture sunlight to generate electricity.
b). A hybrid car charges its batteries as it decelerates. 2. Falling water turns a turbine to generate electricity.
c). Airplane flaps use air resistance to slow down for landing. 2. Rising steam turns a turbine to generate electricity.
d). An electric train requires less electrical energy as it decelerates. 2. A parachute captures air to slow a skydiver’s fall.