21. A solid rod is hanged by a wire attached to its right, as shown in the figure. The left of the rod contacts the wall with friction force. If the coefficient of static friction is μs, what is the maximum value of θ that the rod can keep stable?
(A) θ = tan⁻¹ μs
(B) θ = cot⁻¹ μs
(C) θ = sin⁻¹ μs
(D) θ = cos⁻¹ μs
(E) θ = sec⁻¹ μs

答案:登入後查看
統計: 尚無統計資料