1. The problem statement, all variables and given/known data A rule often used in shaft design states that the angle of twist shall not exceed 1° on a length equal to 20 diameters. What stress in the material does this imply if the modulus of rigidity is equal to 80 × 103 N/mm2 ? 2. Relevant equations T/J=Gθ/L=τ/r J=π?32(D^4-d^4) G=shear stress/shear strain shear stress=F/A F=Wx9.81 3. The attempt at a solution so i found that the length of the beam is D(20) letting D equal its diameter so i got the equation (80x10^3)/(D(20)=Wx9.81Xπ(D/2)/(D/2) but im not sure if thats right or how to solve when there is two unknowns?