Distinguish between kinectic energy and potential energy.
Kinetic energy is energy of motion. A moving object has it. An object that’s not moving has no kinetic energy.
Potential energy is the ability to do work that something has, even though it’s just sitting there and not actually doing it. For example:
— A stone or a bowling on a high shelf or on top of a mountain has gravitational potential energy. It can do work whenever you decide to push it off the shelf and let it fall, or let it roll down the mountain.
— A wound-up spring or a stretched rubber-band has elastic potential energy. It can do work whenever you release it and let it sproing back to its normal unstretched shape.
— A can of gasoline or a stick of wood is loaded with chemical potential energy. It can do a huge amount of work when you mix it with oxygen, and make one little corner of it hot enough to start burning. Then the chemical energy comes pouring out of it.
— Same with dynamite, gunpowder, C4, and all the other explosives.
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