rotation of beam

例句：

1. 1.The car's engine is turning over smoothly.
   汽车的引擎平稳地运转着。
2. 2.The earth rotates on its axis every day.
   地球每天绕其轴旋转。
3. 3. The machine's gears are rotating at a high speed.
   这台机器的齿轮以高速旋转。