英文:Our flag is raised to the top of a pole by a rope and two pulley.
中文:我们的旗帜被用一根绳子和两个滑轮升到了竿顶。
英文:A simple device, such as a lever, a pulley, or an inclined plane, that alters the magnitude or direction, or both, of an applied force; a simple machine.
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