Aball is dropped from the top of a building. it initially moves at 4.0 m/s. after 0.5 seconds, it moves at 3.8 m/s. what force is responsible for the slowing of the ball? air resistance gravity normal tension

Independent variable is something that is changed in a experiment. 

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.