Shown below is a configuration of a circle and a rigid rod. The length of the rod PQ is equal to the circumference of the green circle. The rod tangentially revolves around the circle till point Q reaches point P. Which option represents the CORRECT tracing of point Q?
A
B
C
D
This question is about the curve a point traces when a taut rod unwinds while staying tangent to a circle. That curve is a classic involute construction.
The free rod length keeps falling from the full circumference down to zero as the rod winds. Only option C shows a curve that behaves this way and lands exactly on P.
the correct answer is Option C.








