Why should that apple always descend perpendicularly to the ground, thought he to himself... Why should it not go sideways, or upwards?

他心想，为什么苹果总是垂直落到地面？

youdao

Such surfaces reflect most of the bats' echolocation energy away from it, but some energy hits the surface perpendicularly, sending an echo back directly beneath the bat.

这样的平面反射了大部分蝙蝠的声波，但是有一部分能量垂直撞击到表面上，声波回传至蝙蝠。

youdao

About the 15th of May the keel of the new vessel lay along the dockyard, and soon the stem and stern-post, mortised at each of its extremities, rose almost perpendicularly.

5月15日前后，新船的龙骨已经搁在造船所了；不久，船首材和船尾材也已用榫头分别接在龙骨的两头，几乎直立起来。

youdao

"We want to get the lead inside, so instead of chopping the pencil up perpendicularly and exposing just the ends, we strip the wood casing off the outside and expose the length of the lead, " says Litzen.

FORBES: Ethanol

"We're finding that when you rub a natural biological surface that has an orientation - that has a grain, if you will - and you run that grain perpendicularly to the long axis of the ridges, we find a dramatic increase in friction, " Dr Dominy told BBC News.

BBC: Artificial finger tests evolutionary origin of prints