From the common mechanical phenomenon, present a theoretical method on how to judge the direction of static friction force.

本文以常见的力学现象为例，从理论上阐述判断静摩擦力方向的方法及作功问题的证明方法。

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The dependence of the static friction force on a rod immersed in granular matter on the filling height of granules and the diameter of the rod is studied experimentally.

通过实验研究了圆棒在颗粒物质中受到的摩擦力与颗粒填充高度及棒径的关系。

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One other embodiment has one piezoelectric element, one resistance part connected to the piezoelectric element and one rod normally fixed by means of static friction force.

在另一实施例中， 一压电元件与一阻力件相接，该阻力件与该杆件以静摩擦力相接触而固定；

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