When I push on my refrigerator, there is a force acting on it that wasn't there before. That means it should be experiencing an unbalanced force and begin to move. Why doesn't it?
The reason your refrigerator doesn't move when you push on it, even though there is an unbalanced force acting on it, is due to the presence of static friction.
Static friction is the force that prevents an object from sliding or moving when a force is applied to it. It occurs when there is no relative motion between two surfaces in contact. In the case of your refrigerator, the static friction between the refrigerator and the floor provides an opposing force to your push. This counteracting force matches the force you apply, resulting in no net force being exerted on the refrigerator.
Static friction is typically stronger than kinetic friction (the friction when two surfaces are sliding against each other). It allows objects to stay in place unless a force greater than the maximum static friction is applied. This is known as the "limiting friction" or "maximum force of friction." When the applied force exceeds the limiting friction, the object will start to move.
So, in the case of your refrigerator, unless you exert a force greater than the maximum static friction between the refrigerator and the floor, it will remain stationary despite the presence of an unbalanced force.