Question

A line of length 15 cm at first lied on the vertical plane parallel to horizontal plane and then keeping one of its ends fixed turned 30 degrees with respect to horizontal plane and then turned 50 degrees with respect to vertical plane. What is the length of the line in top view?

(a) 9.6 cm

(b) 7.5 cm

(c) 12.99 cm

(d) 11.49 cm

This question was addressed to me in semester exam.

My enquiry is from Projection of Line Inclined to both the Planes topic in division Projection of Lines of Engineering Drawing

Answer 1

Right option is (c) 12.99 cm

The explanation is: First imagine the line in vertical plane parallel to horizontal plane as here we are asked to find the top view’s length so even if the line is rotated with respect to the horizontal plane the line length will not change and then rotated with respect to the vertical plane which is calculated as follows 15 x cos (30) =12.99 cm.