Question

If the polar moment of inertia of a shaft is doubled keeping length same, then torque required to produce the same angle of twist

Answer 1

Answer:

If you are asking about the shaft which can resist the torsion load more with the same resisting area (same weight), than the answer should be Hollow shaft.

If you see the shear stress diagram of a shaft on application of torque it

Here, you can see that the maximum shear stress applied is at the outer diameter, so the elements at the outer diameter is contributing it's full resistance force to the torque applied. while at the inside the elements are not applying it's full resistance thus causing waste of their strength.