phy tension problem

2010-01-01 11:39 pm

圖片參考：http://imgcld.yimg.com/8/n/HA00086912/o/701001010265613873389880.jpg

係呢幅圖道
點解T3=2W
但係T1同T2唔等如2W

T3唔係垂直2W, 如果將T3 折COMPONENT, 咪T3 sinθ 先係等如2W
點解會咁ge??

回答 (1)

天同

2010-01-02 12:52 am

✔ 最佳答案

If T3.sin(θ ) = 2W, then T3 = 2W/sin(θ ), i.e. T3>2W
The weight 2W will then go up and equilibrium is not reached, but that will contradict to the given condition.

The fact is that if you resolve T3 into verical and horizontal components at point D, there is NO force to counter-balance the hroizotnal component T3.cos(θ).

For T1 at point B, its vertical component is balanced by W and horizontal component is balanced by T2.

Likewise, at point C, the vertical component of T3 is balanced by W' and horizontal component by T2.

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