Final answer:
The axis notation runs from the origin outwards in both positive and negative directions. In 3D space, the right-hand rule is used with the thumb, index, and middle fingers representing the x, y, and z axes, respectively.
Step-by-step explanation:
When facing a point (or pt), the notation of the axis runs from the origin, which is typically at the center where all axes intersect, and extends outwards in the positive and negative directions. By common agreement, the positive branches of the axes x, y, and z are like the thumb and the first two fingers of the right hand when extended such that they make the largest angles with each other. This is often referred to as the right-hand rule.
The cartesian coordinate system is based on two straight lines, or 'axes,' which are perpendicular to each other on a flat plane. These are the x-axis (horizontal) and the y-axis (vertical). For three-dimensional space, the z-axis is added, representing depth. Points above the plane have a positive z value, while points below it have a negative z value.
Choosing a direction as positive is essential for determining the direction of vectors or calculating forces in physics. For example, in the diagram where the vertical axis is y, upward direction is chosen as positive. Consequently, in the equation Fp - W1 - W2 = 0, the positive and negative signs indicate the directions of the forces involved.