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

把包装放在一个光滑的表面，在腰部高度。

youdao

A smooth surface or track for sliding, usually inclined.

用于滑行的平面或路径，通常是倾斜的。

youdao

A smooth surface or track for sliding, usually inclined.

滑面，滑道：用于滑行的平面或路径，通常是倾斜的。

youdao

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

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In the vacuum, the sharp edges of the lunar soil cling together, leaving a smooth surface much as moist sand does on a beach.

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It revived its fortunes by retargeting itself as a productivity tool for warehouses, security teams at airports and other specialized locations where on-the-job effectiveness did require the ability to glide quietly along a smooth surface at 12 m.p.h.

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In 1969 he created a new curved ice ax, the Piolet, which gave climbers better purchase, say, on the smooth surface of a frozen waterfall.

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