本题目来源于试卷: 2011 美国F=ma物理竞赛 F=ma physics competition，类别为 美国物理杯赛(Physics Bowl)
[单选题]
A turntable is suppor 2 bmobjr(br7 8i4m (bzu9jld8 7nhr h-(9x 9n 0vgffeu1dw;y*rmpz. ated on a Teflon ring of inner radius $R$ and outer radius $R+\sigma(\sigma << R)$, as shown in the diagram. To rotate the turntable at a constant rate, power must be supplied to overcome friction. The manufacturer of the turntable wishes to reduce the power required without changing the rotation rate, the weight of the turntable, or the coefficient of friction of the Teflon surface. Engineers propose two solutions: increasing the width of the bearing (increasing $\sigma$ ), or increasing the radius (increasing $R$ ). What are the effects of these proposed changes?
A. Increasing $\sigma$ has no significant effect on the required power; increasing $R$ increases the required power.
B. Increasing $\sigma$ has no significant effect on the required power; increasing $R$ decreases the required power.
C. Increasing $\sigma$ increases the required power; increasing $R$ has no significant effect on the required power.
D. Increasing $\sigma$ decreases the required power; increasing $R$ has no significant effect on the required power.
E. Neither change has a significant effect on the required power.
参考答案: A
本题详细解析:
暂无
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