Oblique Projection

14 Grade 9 Pre-Technical Studies questions on Oblique Projection, with worked marking schemes. 14 questions are available on this topic in full.

1. Question 1

   1 mark

   A student compares cavalier and cabinet oblique drawings of the same box. The cabinet drawing looks more realistic because

   A. the receding angle is changed to 90 degrees

   B. halving the depth reduces the distorted, stretched appearance

   C. hidden lines are added

   D. the front face is drawn larger

   (1 mark)

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2. Question 2

   1 mark

   In cabinet oblique projection, the receding lines are drawn at 45 degrees but their length is

   A. drawn to full width instead

   B. kept equal to the true depth

   C. reduced to half the true depth

   D. doubled

   (1 mark)

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3. Question 3

   1 mark

   In oblique projection, the front face of an object is drawn

   A. reduced to half its actual size

   B. true to shape and size, facing the viewer

   C. as a hidden dotted outline

   D. at 45 degrees to the horizontal

   (1 mark)

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4. Question 4

   3 marks

   State three reasons why oblique projection is preferred for drawing objects that have curves or circles on one face.

   (3 marks)

   Marking scheme

   Any three (1 mark each): the front face is drawn true to shape/size so circles remain true circles (not ellipses); it is easier and faster to draw than isometric; it requires simpler instruments (45-degree set square); curved detail on the front is not distorted; measurements on the front face can be taken directly.

5. Question 5

   1 mark

   Which is the MAIN advantage of using oblique projection to draw an object with important detail on its front face?

   A. It removes the need for dimensions

   B. The front face is shown in true shape and is easy to draw

   C. It shows the inside of the object

   D. All three faces are equally reduced

   (1 mark)

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6. Question 6

   1 mark

   An object is best represented in oblique projection when

   A. it is a simple flat sheet

   B. it has circular or curved features on the front face

   C. all its faces are equally important

   D. it has no depth

   (1 mark)

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7. Question 7

   1 mark

   When setting out an oblique drawing, which drawing instrument is MOST suitable for producing the 45-degree receding lines accurately?

   A. A flexible curve

   B. A protractor set at 60 degrees

   C. A 45-degree set square

   D. A pair of compasses

   (1 mark)

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8. Question 8

   3 marks

   A learner is drawing a rectangular block measuring 40 mm wide, 30 mm high and 20 mm deep in cabinet oblique projection.

   (a) State the length to which the depth (receding) line should be drawn.

   (b) Give a reason for this length.

   (3 marks)

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9. Question 9

   6 marks

   During a technical drawing lesson, a learner is asked to represent a small rectangular wooden block using oblique projection on paper.

   (a) Explain what is meant by oblique projection. (2 marks)

   (b) State the angle at which the receding (depth) lines are most commonly drawn in oblique projection. (2 marks)

   (c) Name the type of oblique projection in which the depth measurements are drawn to HALF their true size. (2 marks)

   (6 marks)

   Marking scheme

   (a) Oblique projection is a method of pictorial drawing in which the front face of an object is drawn in true shape and size (parallel to the drawing plane), while the depth/receding edges are drawn going back at an angle to show the three-dimensional form of the object. (2 marks) (b) The receding (depth) lines are most commonly drawn at 45 degrees to the horizontal (30 degrees or 60 degrees are also acceptable angles used in oblique drawing). (2 marks) (c) Cabinet oblique (cabinet projection) — the receding/depth lines are drawn at 45 degrees but to half their true length. (2 marks)

10. Question 10

    2 marks

    Distinguish between cavalier oblique projection and cabinet oblique projection.

    (2 marks)

    Marking scheme

    In cavalier oblique the receding lines are drawn full/true length (1); in cabinet oblique the receding lines are drawn at half (reduced) length to give a more realistic appearance (1). (Both keep the front face true and receding lines at 45 degrees.)

11. Question 11

    1 mark

    A learner draws a cube in cavalier oblique projection. The receding (depth) lines are usually drawn at an angle of

    A. 90 degrees to the horizontal

    B. 180 degrees to the horizontal

    C. 15 degrees to the horizontal

    D. 45 degrees to the horizontal

    (1 mark)

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12. Question 12

    3 marks

    Outline three steps a learner should follow when producing an oblique drawing of a simple object.

    (3 marks)

    Marking scheme

    Any three in a logical order (1 mark each): draw the true front face/elevation of the object first; from each front corner draw receding lines at 45 degrees; mark off the depth along the receding lines (full length for cavalier, half for cabinet); complete/join the back edges to form the solid; darken visible outlines and clean up construction lines.

13. Question 13

    1 mark

    A learner is taught how to draw a box in oblique projection during a technical drawing lesson. Which statement correctly describes oblique projection?

    A. All three faces are drawn at 30 degrees to the horizontal

    B. Only the top view is shown without any depth

    C. The object is drawn as separate flat views side by side

    D. The front face is drawn true shape and size, with depth lines drawn at an angle (commonly 45 degrees)

    (1 mark)

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14. Question 14

    1 mark

    A learner is asked to draw an object using oblique projection. Which statement correctly describes how the front face of the object is drawn in oblique projection?

    A. The front face is drawn in true shape and size, facing the viewer

    B. The front face is drawn at 30 degrees to the horizontal

    C. The front face is drawn smaller than the back face

    D. The front face is hidden from the viewer

    (1 mark)

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