Energy is not a single, easily definable entity, but rather an abstract collective conceppt: natural and anthropogenic phenomena.
Heat (therma energy)
Motion (kinetic or mechanical energy)
Light(electromagentic energy)
Chemical energy of fuels and foodstuffs
is associated with all moving masses.
Ek=1/2mv^2——at high speed, small objects can become very dangerous
A change in the spatial setting of a mass or of its configuration物体或者其结构在空间中位置的变化
Gravitational potential energy resulting from a changed position in the earth’s gravitational field
重力发电的一大应用是水力发电，20%的电是通过这种方式获得的
Ep=mgh