Well there are two kinds of energy density measures, energy-unit/volume-unit and energy-unit/weight-unit. For distance, it can be (usually is?) the energy/volu

Well there are two kinds of energy density measures, energy-unit/volume-unit and energy-unit/weight-unit. For distance, it can be (usually is?) the energy/volume that is the limiting factor, but for acceleration, it is the energy/weight as weight is the other balancing factor, besides power, of your acceleration equation.