(2r93？ Yongkang City Simulation) 2RR 9 Since September 9, 2009, the northern and central and western regions of China have ushered in rare snowstorm weather, which has brought serious problems to the

(2r93？ Yongkang City Simulation) 2RR 9 Since September 9, 2009, the northern and central and western regions of China have ushered in rare snowstorm weather, which has brought serious problems to the safe operation of the power grid. Solution:

A, take the conductor between ab as the research object, and exert force as shown in Figure J. From the topic, we can see that α > β, FB > FA, and the tension at point B on the conductor is greater than that at point A, so point B is more easily broken than point A in a snowstorm.

Taking three wires between B and C and the tower and three wires between D and the tower as the research object, the stress diagram is shown in 2 and 3.

& ampnb6p& ampnb6p& ampnb6pFc=Gjaanθ，Fb=G2aanθ

From the topic, GJ < G2, so FC < FB. That is to say, the wire tension at point C is less than that at point D, so B is correct.

C, Zhang Liwei F with two towers on the conductor, as shown in Figure 5, is larger according to the balance condition.

& ampnb6p& ampnb6p& ampnb6p& ampnb6pG=2Fco6α2

Big, the tension of the tower on the conductor is F=G2co6α2. When the transmission line between two towers descends in an arc, α2 decreases, co6α2 increases and F decreases, so the tension in the line can be reduced. So, C is correct.

The wire tension on both sides of tower D and tower 2 is the largest, and the included angle between them is the smallest, so the resultant tension of transmission line is the largest. So, d is wrong.

So choose BC