1) Action force = reaction force when the state is unchanged. For example, pushing a car without pushing, action force = reaction force. For example, if the car is pushed and moves at a constant speed, action force = reaction force. Because the states are all constant. 2) When the state changes, the action force does not = the reaction force. For example, if the car is pushed faster and faster, the action force is greater than the reaction force. If the car is pushed slower and slower, the action force is less than the reaction force until the state remains the same, or until the action force = reaction force. Because the car is getting slower and slower, the power is getting smaller and smaller, resulting in resistance to consume the power of power is getting smaller and smaller, that is, the reaction force is getting smaller and smaller, so it can produce a real state invariant.