In Newtonian mechanics, the net force is the vector sum of all forces acting on a body.
Forces have both magnitude and direction, so they must be added as vectors rather than by simply adding their numerical sizes. Two equal forces pointing in opposite directions produce a net force of zero. Unequal opposing forces leave a net force pointing toward the stronger force, while forces at right angles combine according to vector geometry.
Newton’s second law links net force to acceleration: Fnet = ma for constant mass. A zero net force therefore means zero acceleration, although the object may be at rest or moving with constant velocity. This is the basis of mechanical equilibrium. A free-body diagram helps identify and combine the individual forces, such as gravity, friction, tension, and the normal force.
Net force is not the whole story for an extended object. Forces can produce torque as well as translation, and a body may have zero net force while still rotating if the torques do not cancel. Thus, translational balance and rotational balance are related but distinct conditions.