An open train car rolls along a track while it is being filled with sand. There is negligible friction. As a result of the accumulating sand, what happens to the speed of the train car? (Assume negligible friction and the cart is
just rolling along, not receiving any additional force to regulate its speed.)

Velocity=total displacement/timefrom house to store is 500 from store to neighbor is 200 therefore total displacement=500+200=700metrestherefore,700metres/910seconds=0.8metres per second

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.

Lexy is correct because angle r is between the incident wave,  n  = 0, and a diffracted wave.