三级aa视频在线观看-三级国产-三级国产精品一区二区-三级国产三级在线-三级国产在线

US EUROPE AFRICA ASIA 中文

Unpacking the mystery of wobbly suitcase syndrome

Updated: 2017-07-01 09:05:52

You are rushing to catch a train or plane and suddenly the suitcase you're pulling starts to rock from wheel to wheel, threatening to flip over.

Tens of millions of travelers suffer this annoyance every day, but up to now, nobody could say exactly why.

Poor design? Substandard construction? Faulty technique?

Perhaps a bit of each, but the underlying cause lies elsewhere, according to a study published recently in the no-nonsense Proceedings of the Royal Society A: Mathematical and Physical Sciences.

Call it wobbly suitcase syndrome.

"The tendency of a two-wheeled suitcase to oscillate from one wheel to another is due to an inherent mechanical instability," explained senior author Sylvain Courrech du Pont, a researcher at the Complex Materials and Systems Laboratory of Paris-Diderot University.

More precisely, the inbuilt unsteadiness arises at the intersection of types of motion, simulations with toy-scale models and theoretical calculations showed.

"The problem is the interaction"-the clash, in other words-"of rotational and translational motion," Courrech du Pont told AFP.

"It may seem paradoxical, but it is precisely because the suitcase is designed to roll in a straight line that it moves sideways."

Rotational motion occurs when an object, such as a wheel (or two), spins around an axis in a continuous way.

Stop or speed up

Translational motion involves sliding an object-in this case, the whole suitcase-in any direction.

"The wheels constrain the suitcase to roll in a direction that is perpendicular, or at a right angle, to the axis on which the wheels are turning," Courrech du Pont explained.

There is little tolerance for deviation: a sharp change in direction while walking briskly, or a wheel hitting a bump and lifting off the ground, is enough to make the suitcase tip from wheel to wheel.

The same kind of rocking oscillations can occur with any two-wheeled vehicle in which the wheels are on the same axis, such as a hand-truck or a trailer pulled by a car.

What to do? There are two options, according to the study.

One is to stop, stabilize, and start again.

But the suitcase-in theory-will also regain stability if wheel rotation speeds up, though running in an airport may carry risks of its own.

How did this interplay of two basic physics axioms go unnoticed for so long?

"I really don't know," said Courrech du Pont, who set up the experiments as a classroom project for his third-year university students.

"Earlier efforts to study this problem only looked at the motion of a solid block, so they missed the coupling," he said.

Only when he set about preparing a bibliography did he realize that no one had cracked this particular nut.

"The world is full of simple problems like this that are not solved," he added.

AGENCE FRANCE-PRESSE

Editor's Picks
Hot words

Most Popular
...
主站蜘蛛池模板: 国产一级大片 | 精品一区二区久久 | 国产一级特黄aa级特黄裸毛片 | 香港三级理论在线观看网站 | 国产一区在线mmai | a一级毛片 | 久久综合九色综合欧洲 | wwwxxxx黄色| 欧美一级毛片兔费播放 | 亚洲成网站www久久九 | 尤物视频在线观看网站 | 男生j桶进女人p又色又爽又黄 | 国产一二三区在线观看 | 国产精品黄色片 | 91精品国产综合久久青草 | 日本黄区免费视频观看 | 日韩欧美国产一区二区三区四区 | 亚洲一区二区三区亚瑟 | 日韩在线观看中文字幕 | 国产精品亚洲第一区焦香 | 成人午夜亚洲影视在线观看 | 国产欧美精品一区二区三区四区 | 一区二区不卡视频 | a毛片免费视频 | 亚洲精品入口一区二区在线播放 | 韩国美女丝袜一区二区 | 成人亚洲网站 | 国语一区 | 放几个免费的毛片出来看 | 香蕉国产 | 精品尤物 | 嗯~啊~哦~别~别停~啊黑人 | 情侣在线| 亚洲 欧美 中文 日韩专区 | 久久久久久久综合 | 国产在线拍国产拍拍偷 | 国产午夜视频在永久在线观看 | 成人夜夜嗨 | 欧美精品黄页免费高清在线 | 欧美精品国产日韩综合在线 | 亚洲一级毛片免费在线观看 |