Question

The curve generated by a point on the circumference of a circle, rolling along another circle inside it, is called a ________

(a) Epicycloid

(b) Epitrochoid

(c) Hypocycloid

(d) Trochoid

I have been asked this question during a job interview.

Enquiry is from Curves Used in Engineering Practice topic in portion Lettering Practice, Scales & Curves of Civil Engineering Drawing

Answer 1

Right option is (c) Hypocycloid

To explain I would say: Hypocycloid is a special plane curve generated by the trace of a fixed point on a small circle that rolls within a larger circle. It is comparable to the cycloid but instead of the circle rolling along a line, it rolls within a circle. In the figure below, the circle with radius b rolls inside the bigger circle thus making the curves known as hypocycloid.