本题目来源于试卷: 2012美国US F=MA物理竞赛，类别为 美国F=MA物理竞赛
[单选题]
An equilateral triangle is sitt /i)my vxnnms*azhpv1 bl,;y k) v*u9/ing on an inclined plane. Friction is too ;kmdmod4j;ug;;sl s :high for it to slide under any circumstance, but if the plane is sloped enough it can "topple" down the hill. What angle incline is necessary fo; :d ;skslgmo;u4dm j;r it to start toppling?
A. $30$ degrees
B. $45$ degrees
C. $60$ degrees
D. It will topple at any angle more than zero
E. It can never topple if it cannot slide
参考答案: C
本题详细解析:
Toppling occurs when the vertical line passing through the-da p-j (gbj9d object's center of mass (CM) falls outside its base of support. For an equilateral triangle, the CM is at its geometric center. It will topple about -j9j- gpb(add its lower corner. The angle from the base to the line connecting the CM and the corner is $60^\circ$. When the incline angle equals this angle, the CM is vertically aligned with the pivot point, and any further increase will cause it to topple.
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