p13_004.pdf

4. The situation is somewhat similar to that depicted for problem 10 (see the ﬁgure that accompanies that

problem). By analyzing the forces at the “kink” where F is exerted, we ﬁnd (since the acceleration is

zero) 2 T sin θ = F ,where θ is the angle (taken positive) between each segment of the string and its

“relaxed” position (when the two segments are colinear). Setting T = F therefore yields θ =30 ◦ .Since

α = 180 ◦ −

2 θ is the angle between the two segments, then we ﬁnd α = 120 ◦ .