本题目来源于试卷: Electrostatic Force and Electric Field，类别为 美国物理杯赛(Physics Bowl)
[单选题]
94.39: A small object with charge q and weight mg is atta n 7pkb:tp/mttf /g6e0ched to one end of xyr-/ c0y7b+2lw xqbpa string of length L. The other end is attached to a stationary s /wyy0cb 2rx q7px+l-b upport. The system is placed in a uniform horizontal electric field E, as shown in the accompanying figure. In the presence of the field, the string makes a constant angle q with the vertical. What is the sign and magnitude of q?
A. positive with magnitude mg/E
B. positive with magnitude mg tanθ/E
C. negative with magnitude mg/E
D. negative with magnitude mg tanθ /E
E. negative with magnitude E tanθ /mg
参考答案: B
本题详细解析:
暂无
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