Problem 1.61

Two touching bars 1 and 2 are placed on an inclined plane forming an angle $\alpha$ with the horizontal (Fig. 1.10). The masses of the bars are equal to $m_{1}$ and $m_{2},$ and the coefficients of friction between the inclined plane and these bars are equal to $k_{1}$ and $k_{2}$ respectively, with $k_{1}>k_{2} .$ Find: (a) the force of interaction of the bars in the process of motion; (b) the minimum value of the angle $\alpha$ at which the bars start sliding down.