求向心力的量值
我正係識計法向反作用力=5200N,答案話向心力係4330N,但我實在唔知點計出黎,唔該幫幫手比個步驟我睇thz!
更新1:
但係本野既答案話係4330N..
中四物理問題,實在不會解
2012-06-02 6:05 am
一輛車在傾斜路面轉入曲率半徑為120m的彎角.汽車的重量和作用於汽車的摩擦力分別是6000N和2000N.路面的傾斜角度是30度。
求向心力的量值
我正係識計法向反作用力=5200N,答案話向心力係4330N,但我實在唔知點計出黎,唔該幫幫手比個步驟我睇thz!
求向心力的量值
我正係識計法向反作用力=5200N,答案話向心力係4330N,但我實在唔知點計出黎,唔該幫幫手比個步驟我睇thz!
回答 (3)
2012-06-03 9:07 am
✔ 最佳答案
Your question is ambiguous. I suppose there should be a diagram showing the direction of frictional force, which could be pointing inward or outward.Assume the frictional force Ff is pointing inward towards the centre. Resolve it into two components, a horizontal component Ff.cos(30) and a vertically downward component Ff.sin(30).
Hence, consider the upward forces,
R.cos(30) = 6000 + 2000.sin(30)
where R is the normal reaction
solve for R gives R = 8083 N
[Notice that in a circular motion of a car, the normal reaction must be greater than or equal to the weight of the car, your calculated normal reaction is definitely wrong.]
Hence, centripetal acceleration
= R.sin(30) + 2000cos(30)
= 8083.sin(30) + 2000.cos(30) N
= 5774 N
I doubt if your given answer is correct.
2012-06-02 8:11 am
[IMG]http://i331.photobucket.com/albums/l445/asd256_2008/PHY.png[/IMG]
2012-06-04 11:44:15 補充：
天同answer 先係正確答案.我冇理個friction先計到4330
2012-06-04 11:56:42 補充：
同埋唔應該拆mgx_x 計唔到落去
2012-06-04 11:44:15 補充：
天同answer 先係正確答案.我冇理個friction先計到4330
2012-06-04 11:56:42 補充：
同埋唔應該拆mgx_x 計唔到落去
2012-06-02 7:39 am
我算出來是1154N耶
收錄日期: 2021-04-29 17:46:53
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120601000051KK00546