# Civil Engineering Drawing Questions and Answers – Projections of Planes

This set of Civil Engineering Drawing Multiple Choice Questions & Answers (MCQs) focuses on “Projections of Planes”.

1. Planes are formed when any three _________ points are joined.
a) non-collinear
b) collinear
c) concentric
d) eccentric

Explanation: A plane is as two dimensional surface having length and breadth with negligible thickness. They are formed when any three non-collinear points are joined. Planes are bounded by straight/curved lines and may be either regular or an irregular. Regular plane surface are in which all the sides are equal. Irregular plane surface are in which the lengths of the sides are unequal.

2. When the plane surface is held with its surface parallel to one of the planes of projection, the view of the plane surface projected on it will be in __________
a) apparent shape
b) point shape
c) true shape
d) line shape

Explanation: When the plane surface is held with its surface parallel to one of the planes of projection, the view of the plane surface projected on it will be in true shape because all the sides or the edges of the plane surface will be parallel to the plane of projection on which the plane surface is projected.

3. When a plane surface is inclined to any plane of projection, the view of the plane surface projected on it will be its ____________
a) point shape
b) true shape
c) straight line
d) apparent shape

Explanation: An inclined surface is a surface that is perpendicular to one of the principal planes, and is at some angle to the remaining two principal planes. As such, an inclined surface will always appear as a line in one of the principal views and as a foreshortened area in the other two views. An inclined surface will not appear true size in a principal view.

4. A plane surface may be positioned in space with reference to the three principal planes of projection in any of the following positions, which one is false?
a) Parallel to one of the principal planes and perpendicular to the other two
b) Perpendicular to one of the principal planes and inclined to the other two
c) Parallel to both the planes
d) Inclined to all the three principal planes

Explanation: Planes may be divided into two main types: Perpendicular planes and Oblique planes.
And this perpendicular plane is further divided into three parts- a) Parallel to one of the principal planes and perpendicular to the other two. b) Perpendicular to one of the principal planes and inclined to the other two. c) Inclined to all the three principal planes.

5. An equilateral triangular lamina of 25 mm sides lies with one of its edges on HP such that the surface of the lamina is inclined to HP at 60 deg. The edge on which it rests is inclined to VP at 60 deg. How many lines with 3 coordinates will appear during the projection?
a) 5
b) 6
c) 3
d) 2

Explanation: Lines above xy line i.e. a’b’(c’) representing lines are the required lines, refer the figure below.

6. A circular lamina inclined to the VP appears in the front view as an ellipse of major axis 30mm & minor axis 15 mm. The major axis is parallel to both HP and VP. One end of the minor axis is in both the HP and VP. Determine the inclination of the lamina with the VP.
a) 45o
b) 90o
c) 60o
d) 105o

Explanation: On measuring the value of φ by making the projection, its value is found.

7. A hexagonal lamina of 30 mm sides rests on HP with one of its corners touching VP and the surface inclined at 45 deg. to it. One of its edges inclined to HP at 30 deg. What will be the value of α?
a) 32.31°
b) 42.32°
c) 52.32°
d) 62.32°

Explanation: Referring the figure below, on measuring the value of α, inclination is known.

8. A rectangular lamina of sides 20 mm X 25mm has an edge in HP and adjoining edge in VP, is tilted such that the front view appears as a rectangle of 20 mm X 15 mm. The edge which is in VP is 30 mm from the right profile plane. Find its inclinations with the corresponding principal planes.
a) 43.43o
b) 53.13o
c) 43.13o
d) 67.34o

Explanation: Referring the figure below, on measuring the value of φ, inclination is known.

9. A mirror 30 mm X 40 mm is inclined to the wall such that its front view is a square of 30mm side. The longer side of the mirror appear perpendicular to both HP and VP. Find the inclination of the mirror with the wall.
a) 48.76o
b) 36.78o
c) 51.76o
d) 41.41o

Explanation: Referring the figure below, on measuring the value of φ, inclination is known.

10. When a plane is perpendicular to a reference plane, its projection on that plane is a __________
a) straight line
b) true line
c) apparent line
d) point

Explanation: Top views of the two end points of a line, when joined, give the top view of the line. Front views of the two end points of the line, when joined, give the front view of the line. Both these Projections are straight lines.

Sanfoundry Global Education & Learning Series – Civil Engineering Drawing.

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