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標題: [Phy] mechanics(88ALQ2&07ALQ2) [打印本頁]

作者: qwer 時間: 2016-4-5 12:23 AM 標題: mechanics(88ALQ2&07ALQ2)

88ALQ2
A smooth block of mass 2 kg slides down a wedge. The wedge, of mass 10 kg, is placed on a horizontal table, and its inclined plane makes an angle of 30º with the horizontal. If the wedge remains stationary all the time, the normal reaction of the table acting on the wedge is
Ans:115N (20cos30cos30+100)
07ALQ2
A wedge of mass M is fixed to the ground. A block of mass m slides down the wedge with constant velocity. What is the normal reaction exerted by the ground on the wedge?
Ans

M+m)g

Why the method of calculation is different?How to decide which method should be used?

作者: yeungwk91 時間: 2016-4-5 12:23 PM

88ALQ2
smooth block = > move with const acceleration
=> no friction
07ALQ2
const. velocity => friction

作者: qwer 時間: 2016-4-16 09:15 AM

Why the method of calculation is different?How to decide which method should be used?
Thanks

作者: antonyluk 時間: 2016-4-20 03:03 PM

引用:

原帖由 qwer 於 2016-4-16 09:15 AM 發表
Why the method of calculation is different?How to decide which method should be used?
Thanks

沒有different, 問題應該出於你沒有清楚地畫好free body diagram就去計, 你試下畫下free body diagram先啦

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