The tests were conducted before and after the mass of the model was augmented with iron ballast. to meet the similitude requirements for gravity force and mass c…

为了达到模型相似要求，用铁块作为配重施加于模型上。上述试验项目是在配重施加前后分别进行的。配重前后的模型试验结果与理论分析结果符合良好。

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He grabbed an iron crowbar that was lying on the ballast and, with precise aim, thrust it between the spokes of one of the rapidly revolving front wheels.

NEWYORKER: Among Animals and Plants