Halliday, Resnick & Walker — Force and Motion-II: Problem 22

22 In Fig. 6-28a, a sled is held on an inclined plane by a cord pulling directly up the plane. The sled is to be on the verge of moving up the plane. In Fig. 6-28b, the magnitude \(F\) required of the cord’s force on the sled is plotted versus a range of values for the coefficient of static friction \(\mu_s\) between sled and plane: \(F_1 = 2.0 \text{ N}\), \(F_2 = 5.0 \text{ N}\), and \(\mu_2 = 0.25\). At what angle \(\theta\) is the plane inclined?