pendulum bob的用法和樣例：
例句
- The hydrometric pendulum is sometimes used to determine flow velocities in open channels.
測流速的擺錘有時用於確定明渠中的流速。 - Huygens saw that a pendulum traversing a circular arc completed small oscillations faster than large ones.
惠更斯觀察到，若擺錘沿著圓弧擺盪，那麽擺動幅度小的時候會比幅度大時振蕩得快。
