1. A bob of mass m is suspended from the ceiling with an inextensible and light string. It is released from X as shown. When the bob swings to Y, its kinetic energy (K.E.) is
http://i617.photobucket.com/albums/tt257/michaelcoco_/745ebc3d.jpg
The answer is mg L(1 – cos θ).
※試列明計算步驟※
一條關於物理的簡單問題
2010-04-11 7:36 am
回答 (2)
2010-04-11 7:58 am
✔ 最佳答案
P.E._x + K.E._x = P.E._y + K.E._ymgh_x + 0 = mgh_y + K.E._y
K.E._y = mgh_y - mgh_x
K.E._y = mgL - mgLcosθ
K.E._y = mgL(1-cosθ)
2010-04-10 23:59:18 補充：
你用睇triangle 既方法,會睇到X,Y,同頂點係直角三角形
參考: Hope can help you^^”
2010-04-11 8:02 am
The vertical distance of X with respect to Y
= L - L.cos(θ)
hence, loss of potential energy when the bob falls from X to Y
= mg[L - L.cos(θ)] = mg.L(1 - cos(θ))
Therefore, the gain in kinetic energy = loss of potential energy
= mg.L(1 - cos(θ))
= L - L.cos(θ)
hence, loss of potential energy when the bob falls from X to Y
= mg[L - L.cos(θ)] = mg.L(1 - cos(θ))
Therefore, the gain in kinetic energy = loss of potential energy
= mg.L(1 - cos(θ))
收錄日期: 2021-04-29 17:34:39
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100410000051KK01835