因为它们的两副翅膀叠在一起，在空气动力学的理论中，这意味着它们对自己身体缺乏控制力。

Because their two sets of wings effectively flap as one, that in theory gives them little control over the aerodynamic forces on their body.

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其他的一些研究人员，如威斯康星大学的伊丽莎白·罗伯茨(Elizabeth Roberts)和她的同事，已经做了踢球的动力学分析，同时考虑到力的作用。

Other researchers, such as Elizabeth Roberts and co-workers at the University of Wisconsin, have done dynamic analyses of kicking, taking the forces involved into account.

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的确鸟儿尾巴一样的飞机尾部改善了空气动力学性能，缓解了机体和机翼的阻力，同时还大大的增加了向上的力，缓释了由于飞机本身和货物重量而产生的向下的力。

But it was a birdlike tail that really amped up the aerodynamics, dampening the drag from the body and wings, as well as boosting the lift that lags under vehicle weight and cargo load.

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