고체역학 (Beer) — Torsion: Problem 3.149

3.149 Equal torques are applied to thin-walled tubes of the same length \(L\), same thickness \(t\), and same radius \(c\). One of the tubes has been slit lengthwise as shown. Determine (a) the ratio \(\tau_b / \tau_a\) of the maximum shearing stresses in the tubes, (b) the ratio \(\phi_b / \phi_a\) of the angles of twist of the tubes.