Common sense push and pull are

Push and pull are elastic deformations.

After an object is deformed by an external force, if the external force is removed, the force by which the object can return to its original shape is called "elastic force". Its direction is opposite to the direction of the external force that causes the object to deform. Because objects can deform in many different ways, the elastic force produced also comes in various forms. For example, if a heavy object is placed on a plastic plate, the bent plastic will return to its original shape and generate upward elasticity. This is its supporting force for the heavy object. Hang an object on a spring, and the object stretches the spring. The stretched spring returns to its original shape, producing an upward elastic force. This is its pulling force on the object. Not only plastics, springs, etc. can deform, but any object can deform. There is no object that does not deform. However, some deformations are more obvious and can be seen directly; some objects are relatively hard and have very small deformations, which can only be detected with a microscope.

The change in shape or volume of an object under the action of force is called deformation. The deformation that can return to its original shape after the external force stops acting is called elastic deformation. When a deformed object returns to its original shape, it exerts a force on the object in contact with it. This effect is called elasticity. That is, within the elastic limit, the force exerted by an object on the force exerting the object to deform is called elastic force.

Elastic force is a contact force. Elastic force can only exist where objects are in contact with each other, but elastic force does not necessarily exist between objects in contact with each other. Because the generation of elasticity requires not only contact, but also interaction.

Elastic force occurs between objects that are in direct contact and undergo elastic deformation. The commonly referred to as pressure, support, and tension are elastic forces. The direction of elastic force is always opposite to the direction of deformation of the object. The direction of pressure or support force is always perpendicular to the support surface and directed toward the object being pressed or supported.

What is usually called tension is also elasticity. The tension of the rope is the elastic force of the rope on the object being pulled. The direction is always along the rope and points in the direction of the rope contraction.

When the spring deforms elastically, within the elastic limit, the size of the elastic force is proportional to the length of the spring extension (or shortening) (or the extension of the spring is proportional to the tensile force), that is, F= -kx (or △F=-k△x). Among them, k is called the stiffness coefficient of the spring (also called the strength coefficient or elastic coefficient), which is numerically equal to the elastic force when the spring is extended (or shortened) per unit length. The unit is Newton per meter and the symbol is N/m. The k value is related to the properties of its material. The difference between soft and hard springs refers to their different stiffness coefficients. And the stiffness coefficients of different springs are generally different. The negative sign in the above expression means that the elastic force generated by the spring is in the opposite direction of its elongation (or compression). This law was discovered by British scientist Hooke and is called Hooke's law.

As long as any object undergoes elastic deformation, it will definitely produce elastic force on the objects in contact with it. Once it exceeds the elastic deformation range, it will completely lose its elasticity. This deformation that exceeds its elastic bearing range is called "normal deformation". (That is, exceeding the elastic limit, except for plastic objects)

The essence of elasticity is the force between molecules. When an object is stretched or compressed, the distance between the molecules will change, causing the relative positions of the molecules to pull apart or move closer together. In this way, the attraction and repulsion between the molecules will not be balanced, and there will be a tendency to attract or repel each other. , and the total effect of attraction or repulsion between these molecules is the elasticity observed on a macroscopic scale. If the external force is too great and the distance between molecules is stretched too far, the molecules will slide into another stable position. Even after the external force is removed, they cannot return to their original position and will retain permanent deformation. This is the nature of elasticity.

I hope I can help you clear up your doubts.