Problem 1.306

Calculate the torque $N$ twisting a steel tube of length $l=$ $=3.0 \mathrm{~m}$ through an angle $\varphi=2.0^{\circ}$ about its axis, if the inside and outside diameters of the tube are equal to $d_{1}=30 \mathrm{~mm}$ and $d_{2}=$ $=50 \mathrm{~mm}$