The Torsion Pendulum
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Torsional Stiffness
Torsional stiffness indicates how much effort is required to twist the spring steel wire.  The stiffness depends on several of the wire's properties:

Cross sectional shape and area (larger = stiffer)

Length of wire (longer = less stiff)

The material of which the wire is made (springs having the same shape but made of different materials will have different stiffnesses)

Spring steel wires of the size and length I use have a torsional stiffness values of around 0.350 to 0.400.