Final answer:
The student is instructed on how to draw the projections of a given line AB on the horizontal and vertical planes when the line is parallel to both of these planes. The steps include setting up a reference ground line, plotting the distance of point A above Hp, and drawing a line segment equal to the length of AB on each plane.
Step-by-step explanation:
The question involves a practical application of drawing projections in technical drawing, which is typically covered in engineering or technical drawing courses. The student is asked to draw the projections of a line AB, which is 60mm in length. This line has its end A at 20mm above the horizontal plane (Hp) and the end B 30mm in front of the vertical plane (vp). The key here is to understand that because the line is kept parallel to both Hp and vp, its projections on these planes will be lines of the same length as AB, since there is no change in length when projecting a line parallel to the plane.
Step-by-step Drawing of Projections
1. Draw a horizontal reference line that represents the ground line, separating the horizontal plane on top and the vertical plane below.
2. Mark point A on the ground line, which will be the projection of point A from the given line AB.
3. Measure 20mm above this point to represent the true distance of A above the Hp. This is because it is kept parallel to Hp.
4. From point A, draw a 60mm horizontal line parallel to the ground line in both directions to represent the true length of the line in projection.
5. Now from point B's projection on the ground line, measure 30mm in front of the vertical plane.
6. The final step is to connect the points that represent the vertical and horizontal distances to the corresponding ends of the 60mm line, which would represent the line AB in true length and position.
Since the line is parallel to both planes, there is no foreshortening effect. This means that the projection on the Hp will be a line segment 60mm long and the projection on the Vp will be the same length.