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標題: 中六Physics friction問題..高手解答THX [打印本頁]

作者: 2c細成 時間: 09-4-18 10:43 AM 標題: 中六Physics friction問題..高手解答THX

作者: 無聊的＊晶＊ 時間: 09-4-18 08:58 PM

(c):Mgsin30>F, so we need a force P to prevent the block from moving downward...
So,F+P=Mgsin30,F & P must in the same direction....
I think...

If we remove P,Mgsin30 and friction are in opposite direction and the block will move downward, so friction and mgsin30 must in opposite direction...

I'm not sure at all,i'm not高手...

[ 本帖最後由無聊的＊晶＊於 2009-4-18 09:03 PM 編輯 ]

作者: Why? 時間: 09-4-19 01:26 AM

個block向下行嘛, 咁咪有個向下既force act on 個plane
咁個plane咪比番向上既reaction force(friction)頂番住佢

作者: 紫魂傲=] 時間: 09-4-19 05:58 PM

P+F岩岩好夠prevent佢moving down 唔洗再用額外既力

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