Acosmic ray travels 60 km through the earth’s atmosphere in 400 μs, as measured by experimenters on the ground. how long does the journey take according to the cosmic ray?

Pe = 1/2k(x)^2  and .05n/m = .05x10^-9m = x 

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.