Answer-
a. I have learnt -Torsional rigidity, Breaking twist, Shear modulus.
b. The twist for breaking of a yarn is called breaking twist. It also can be defined as the number of twists required to break a yarn. Breaking twist depends on the diameter of fiber and it is inversely proportional to its diameter.
That is, Tb ∞ 1/d
Where, Tb = Breaking twist,
d = diameter of fiber.