Correct answer: 17.3 m/s
The velocity of B can be determined using the constraint relation for the rigid rod. The velocity components of A and B must satisfy the condition that the length of the rod remains constant. Using trigonometry, the velocity of B is given by v_B = v_A / sin(α). Substituting v_A = 10 m/s and α = 60°, we get v_B = 10 / sin(60°) = 10 / (√3/2) = 20/√3 ≈ 17.3 m/s.