把包装放在一个光滑的表面，在腰部高度。

Put the pack on a smooth surface, at waist height.

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莱佛士的猪笼草来自婆罗洲的丛林，它产出的花蜜既能吸引昆虫，又能形成一个光滑的表面，让昆虫无法找到着力点。

Raffles' pitcher plant, from the jungles of Borneo, produces nectar that both lures insects and forms a slick surface on which they can't get a grip.

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这种油漆能附着于任何粗糙或光滑的表面。

This paint will adhere to any surface, whether rough or smooth.

《新英汉大辞典》

Somehow, if you could manufacture a really smooth frictionless surface, that if you took a hockey puck or something and an air cushion and you give it a push, in some idealized world, it'll travel forever.

如果你制造一个绝对光滑无摩擦的表面,然后在上面放个冰球或者别的什么,或者气垫,然后推它一下,在理想条件下,它会永远运动下去

耶鲁公开课 - 基础物理课程节选