Final answer:
An object speeds up in a gravitational field by converting its gravitational potential energy into kinetic energy as it falls, resulting in increased speed and kinetic energy.
Step-by-step explanation:
When an object is observed to speed up in a gravitational field, the most accurate description of what is happening is that the object is falling in the gravitational field, so it has gained kinetic energy. This process occurs because gravitational potential energy is converted into kinetic energy. As the object descends without friction, it accelerates and its potential energy decreases, resulting in an increase in speed. This relationship between potential and kinetic energy is represented by the equation AKE = -APEg, where AKE is the change in kinetic energy and APEg is the change in gravitational potential energy.
For example, when a football falls toward Earth, the work done on the football by gravity is positive, indicating both the displacement and the gravitational force point vertically downward. As the ball speeds up, its kinetic energy increases, showing the conversion from gravitational potential energy back into kinetic energy.
The correct answer to the question is B. The object is falling in the gravitational field, so it has gained kinetic energy.