For the following question, imagine the book drops in free fall and falls a distance d.
1. For the system of the book and earth, the change in total energy of the system if the book falls a distance d.
O positive.
O is negative.
O is zero.
O has a sign which cannot be determined.
2. For the system of the book and earth, the network done on the system by external forces as the book falls a distance d.
O is positive.
O is negative
O is zero.
O has a sign which cannot be determined.

stands for electromotive force and it is measured in volts. despite its name, it is not actually the force in the sense of being a "pushing" or "pulling" (not measured in newtons).an equation that relates emf,  ℰ,  to a battery's terminal voltage, v, current, i, and internal resistance, r, is    ℰ = v + irin this case, the emf can be interpreted as a voltage—a difference in electric potential.i would not say that it would be considered an energy. if emf can be defined as the energy/work per a unit charge from a battery or other electric source, then it is not strictly energy.

B) erini just took the test and it is correct

The best answer i can think of is b