Question

In a regular cone, the angle between base and slanting surface is 60 degrees and the base diameter is 75 mm. If a helix is to be build on such a cone up to half of cones height with 6 revolutions in it. Pitch of the helix is?

(a) 10.8

(b) 5.4

(c) 6.4

(d) 12.9

I got this question in an internship interview.

This intriguing question comes from Helix upon a Cone topic in chapter Curves used in Engineering Practice of Engineering Drawing

Answer 1

The correct answer is (b) 5.4

Best explanation: Height of cone = diameter/2 x tan (angle) = 75/2 x tan (60) = 129.9mm/2= 64.95 mm. Half height is 32.475 mm. Helix made 6 revolution is this height so one revolution height is 32.475/6 = 5.4 mm which is the pitch of the helix.