Attach a sharp stone to the end of astout piece of wood, and with this lever you can hugely increase thespeed, force, effectiveness and safety with which the axe can bewielded.

将一块带有尖刃的石器和一根强壮的树枝接在一起，利用这根长矛人类可以极大地提高速度、力度、效率和安全性。

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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.

机械装置一个简单装置，如杠杆、滑轮或斜面刨，可以改变作用力的大小或方向或同时改变；简单机械装置。

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The force needed at one end of the lever to move the load at the other end of the lever depends on the distances to the pivot.

杠杆的一端所需要的、去移动另一端的东西的力，取决于与支点的距离。

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Similarly, the Saudis have rejected the use of oil exports to America as a lever to force policy changes.

ECONOMIST: The prince and the president | The