1. Complete the following problem (labeled P.3.5 here). In addition to what is asked, determine J in terms of given geometry (a,b,t).

2. Repeat problem 3.5 for the closed cross-section geometry shown at right. Also, define J in terms of given geometry. Note that the closed C/Shas the same area as the open section, and thus thetwo shafts would weigh the same.

3. Compare the results of parts (a) and (b) by deriving ratios of the max shear stress in the open c/s to the max shear stress in the closed c/s, and the rate of twist for the open section divided by the rate of twist for the closed section in terms of the problem variables. Also, computer numerical values for these ratios for the case a=b, and a/t=10. Comment on the significance of these results.

t N/it t +/N b t < < a, b