15. A wooden rod of uniform cross section and of length l is hinged at the bottom of a tank which is filled with water to a height h = l/3, as shown in right figure. If the density of wood is 0.45 g/cm³, find the angle θ from the vertical at which the rod is in equilibrium.


(A) θ = 60°
(B) θ = 30°
(C) θ = 45°
(D) θ = 37°
(E) θ = 53°

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詳解 (共 1 筆)

#7449327
所以這題只要搞懂一件事就是浮力等於排開液體重
木棒中心為支點,順時針力矩等於逆時針力矩
所以第一步先找凊在水中的棒長
6a5dcc13a1c10.jpg
木棒受到重力和浮力
6a5dcc3c7f624.jpg
然後使用力矩平衡去計算
6a5dcc56986c9.jpg
所以可以解出cita會等於
6a5dcc726f9ce.jpg
ㅤㅤ
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