請高手幫幫忙,,phy beyond2000

2009-12-29 10:44 pm

The diagram shows a heavy plank hinged to a vertical wall at one end and supported by a strut which inclines at θ=60 to the vertical. The weight of the plank is 200kN,Assume that the thrust from strut acts along it's length.Calculate

(a) the thrust from the strut,and,
(b) size and direction of the force at the hinge.

我唔明點解thrust from strut(a)不等於200000/sin 60...

還有,明明plank係horizontal地放著,但why它唔等於thrust x cos60,,反而係要分什麼Rx and Ry??

圖片參考：http://i83.photobucket.com/albums/j315/kinki_chung/phy2000.jpg

回答 (1)

NCY

2010-01-06 2:58 am

✔ 最佳答案

Since the plank exerts a downward inclined force along the strut, T must exert upward inclined along the strut.
This is because these two forces are action and reaction pair according to the Newton ’s Third Law of Motion.

圖片參考：http://i248.photobucket.com/albums/gg191/ncy_0916/phy-beyond2000.jpg?t=1262689074

2010-01-07 16:46:23 補充：
Please refer to the following link if you cannot see the image :
http://s248.photobucket.com/albums/gg191/ncy_0916/phy-beyond2000.jpg

2010-01-07 16:46:39 補充：
Please refer to the following link if you cannot see the image :
http://s248.photobucket.com/albums/gg191/ncy_0916/phy-beyond2000.jpg

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