In physics, when analyzing forces on inclines, the choice of positive and negative directions is flexible and depends on the defined coordinate system. For inclined planes, it is common to align axes with the incline, often making the downward direction negative, but this can be reversed. When a box moves down an incline, friction can be considered positive, while the parallel weight is typically negative, though the perpendicular weight can also be defined as positive based on the chosen coordinate system. The normal force and perpendicular weight must balance each other, influencing their signs. Understanding this flexibility in sign assignment is crucial for correctly applying Newton's second law.
