Definition of force: Force is one of the basic concepts in mechanics, and it is the fundamental reason to change the motion state or deformation of an object. In dynamics, it is equal to the product of the mass and acceleration of an object.

Physical meaning of force: the physical meaning of force is an external cause that changes the motion state or deformation of an object.

Force is the action of objects on objects. Without objects, force cannot exist alone. There may also be a force between two objects that are not in contact. The action of force is mutual.

Nature of force

1. materiality: force is the action of an object (matter, mass) on an object (matter, mass). When an object is acted on by a force, another object will inevitably exert this effect on it, and the force cannot exist independently without this object.

2. Vectorality: Force is a vector with both magnitude and direction.

3. simultaneity: the force is generated at the same time and disappears at the same time.

4. Independence: The action of one force does not affect the action of another force.