Whenever you exert a force on an object, according to Newton's third law of motion, the object exerts an equal and opposite force back on you. This is often referred to as the action-reaction pair of forces.

Mathematically, this relationship can be expressed as:

F12 = -F21

Where F12 represents the force exerted by object 1 on object 2, and F21 represents the force exerted by object 2 on object 1. The negative sign indicates that the forces are in opposite directions.

In simpler terms, when you push on an object, it pushes back on you with the same amount of force, but in the opposite direction. This principle is fundamental to our understanding of forces and interactions in the physical world and has applications in various areas such as mechanics, engineering, and sports.