Unbalanced forces are forces that are not equal in size and act in opposite directions on an object, resulting in a change in motion. When the motion of an object changes, it is due to unbalanced forces acting on it. In contrast, balanced forces are equal in size and opposite in direction, resulting in no change in motion for the object they are acting on. For example, if a person is pushing a wall, and the wall does not move, it means that the person and the wall are exerting balanced forces on each other. On the other hand, if a person pushes a rock into soft soil with a force greater than that of the ground, it is an example of an unbalanced force. Unbalanced forces can make an object at rest start moving, make a moving object stop, or change the direction and speed of the object.