試題詳解

5.Patients with severe leg breaks are often placed in traction, with an external force countering muscles that would pull too hard on the broken bones. In the arrangement shown in the figure, the mass m is 5 kg, and the pulleys can be considered massless and frictionless. Note that sin20° ≈ 0.34 and sin70° ≈ 0.94. What is the horizontal traction force applied to the leg? About

(A) 20 N
(B) 40 N
(C) 60 N
(D) 80 N
(E) 100 N