Forces can be balanced or unbalanced. Balanced forces occur when two equal forces acting on an object in opposite directions cancel each other out, resulting in no net force and no acceleration. Unbalanced forces occur when the forces are not equal, resulting in a net force that causes the object to accelerate in the direction of the larger force. Inertia is an object's resistance to changes in its motion. Objects with greater mass have greater inertia and are harder to accelerate or change the motion of than objects with less mass.