Question

The base diameter of a conical helix is 120 mm and other end diameter is 70 mm. The height of helix is 40 mm. What is the angle between the base and slanting side is?

(a) 58 degrees

(b) 60 degrees

(c) 30 degrees

(d) 45 degrees

I got this question in a national level competition.

My query is from Helix upon a Cone in portion Curves used in Engineering Practice of Engineering Drawing

Answer 1

Right option is (a) 58 degrees

The explanation: Base radius= 60 mm. Other end radius = 35 mm. 60 mm– 35mm = 25 mm. height is 40 mm. tan (angle) = height/ base radius = 40 mm/25 mm = 1.6. Angle = tan-1(1.6) = 57.99 degrees approximately equals to 58 degrees.