Question

A line of length 10 cm at first lied on the horizontal plane parallel to vertical plane and then keeping one of its ends fixed turned 30 degrees with respect to vertical plane and then turned 45 degrees with respect to horizontal plane. What is the length of line in top view?

(a) 5 cm

(b) 7.07 cm

(c) 3.53 cm

(d) 10 cm

This question was addressed to me in final exam.

My doubt stems from Projection of Line Inclined to both the Planes in chapter Projection of Lines of Engineering Drawing

Answer 1

Right answer is (b) 7.07 cm

Explanation: First imagine the line in horizontal plane parallel to vertical plane as here we are asked to find the top view’s length even if the line is rotated within the horizontal plane the line length will not change and then rotated with respect to horizontal plane which is calculated as follows. 10 x cos (45)= 7.07 cm.