10 questions · Form 3 Mathematics Bab 7: Plans and Elevations
A triangular prism with a right-angled triangular cross-section rests on its rectangular base. What is the shape of its Front Elevation when viewed perpendicular to the triangular face?
Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.
1. A triangular prism with a right-angled triangular cross-section rests on its rectangular base. What is the shape of its Front Elevation when viewed perpendicular to the triangular face?
Answer: B
Looking directly at the triangular cross-section face gives an orthogonal projection of a triangle.
2. What is an orthogonal projection?
Answer: B
An orthogonal projection is formed when projection rays from an object intersect the plane of projection at right angles (90°).
3. Why are projection lines (construction lines) drawn lightly in plans and elevations?
Answer: B
Construction lines are thin guidelines used to transfer dimensions and maintain alignment between the Plan, Front, and Side elevations.
4. Which projection shows the view of an object onto a vertical plane from the front?
Answer: C
The Front Elevation is the orthogonal projection onto a vertical plane when looking directly at the front of the object.
5. What is the shape of the plan of a sphere with radius r?
Answer: B
The orthogonal projection of a sphere onto any plane (Plan or Elevation) is a circle of the same radius.
6. What is the orthogonal projection of a straight line segment that is parallel to the projection plane?
Answer: B
When a line is parallel to the plane of projection, its orthogonal projection is a line segment of equal length.
7. Which view allows us to measure the height of a 3D object?
Answer: B
Height is a vertical dimension, which is visible in both the Front Elevation and Side Elevation, but NOT in the Plan (top view).
8. A square pyramid has a base of 6 cm × 6 cm and height of 8 cm. What shape is its Front Elevation when viewed facing one side of the base?
Answer: B
When viewed perpendicular to one of the base edges, the front elevation of a regular square pyramid is an isosceles triangle with base 6 cm and height 8 cm.
9. Which view represents the orthogonal projection of an object onto a horizontal plane as seen from above?
Answer: C
The Plan is the view of an object from directly above, projected onto a horizontal plane.
10. What angle is used for the construction alignment line in the standard 4-quadrant layout for drawing plans and elevations?
Answer: B
A 45° construction line in Quadrant IV is used to project horizontal dimensions between the Plan and Side Elevation.