The force exerted by expanding gases is what propels a shell out of a gun barrel. Suppose a force that has an average magnitude F propels the shell so that it has a speed v at the instant it reaches the end of the barrel.
A) What magnitude force is required to double the speed of the shell in the same gun?

The third hammer 8 pounds

You will hear a hissing sound because of the carbon dioxide escaping the can or bottle

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.