關於動能的問題

Kinetic energy of an object is the energy carried by the object when it is moving.
When the object has mass m and it is moving with speed v, its kinetic energy = 1/2mv^2
Also, this kind of kinetic energy is called mechanical kinetic energy. This is related to the motion(including translation and rotation) of the whole object.

Molecular kinetic energy of a molecule is the energy carried by the molecule when it is moving. As you know, molecule is vibrating in an object. For high temperature, the vibration is more violent. Since vibration of molecule is also a motion, energy can be considered. The energy related is molecular kinetic energy. This energy is used to show us the information about heat. In addition, molecular kinetic energy is a type of kinetic energy. It implies that molecular kinetic energy may / may not equal kinetic energy.

For a moving object, total kinetic energy = mechanical kinetic energy + molecular kinetic energy. However, the molecular kinetic energy is very small. It is normally neglected.