ARROWBIG QUESTIONSWhy Are Manhole C

ARROWBIG QUESTIONSWhy Are Manhole Covers Round?BY ERIN MCCARTHY JANUARY 7, 2015iStockISTOCKIf you’re in the habit of looking down at your feet as you walk, you may have noticed that most manholes, and their covers, are round. Or perhaps you’ve been in a job interview where your prospective employer asked this question (which apparently happens enough that it was included in the third edition of The Complete Idiot’s Guide to Job Interviews). He wants to know about your ability to think on your feet, and isn’t so much interested in the correct answer, but it is a good question. Of all of the potential shapes for manholes, why was a circle chosen?There are a number of reasons, according to Larry Scheckel in his book Ask A Science Teacher: 250 Answers to Questions You've Always Had About How Everyday Stuff Really Works. Manholes are round because “it is the best shape to resist the compression of Earth around it.” Round shapes are easier to manufacture than square or rectangular shapes, and because manhole covers are heavy, being round makes them easier to move from place to place (just roll them!). As an added benefit, workers don’t need to line up the covers with any angles, making round covers easy to slip into place.But perhaps the biggest reason that manhole covers are round is that round covers can’t fall through a circular opening. “For all manholes, there is a ‘lip’ around the rim of the hole, holding up the cover, which means that the underlying hole is smaller than the cover,” Scheckel writes. “A round manhole cover can’t fall through its circular opening, because no matter how you position it, the cover is wider than the hole. But a square, rectangular, or oval manhole cover could fall in if it was inserted diagonally into the hole,” which would be bad news for unobservant pedestrians and drivers alike.

Results (Chinese) 1:

ARROW
BIG QUESTIONS
Why Are Manhole Covers Round?
BY ERIN MCCARTHY JANUARY 7, 2015
iStock
ISTOCK
If you’re in the habit of looking down at your feet as you walk, you may have noticed that most manholes, and their covers, are round. Or perhaps you’ve been in a job interview where your prospective employer asked this question (which apparently happens enough that it was included in the third edition of The Complete Idiot’s Guide to Job Interviews). He wants to know about your ability to think on your feet, and isn’t so much interested in the correct answer, but it is a good question. Of all of the potential shapes for manholes, why was a circle chosen?

There are a number of reasons, according to Larry Scheckel in his book Ask A Science Teacher: 250 Answers to Questions You've Always Had About How Everyday Stuff Really Works. Manholes are round because “it is the best shape to resist the compression of Earth around it.” Round shapes are easier to manufacture than square or rectangular shapes, and because manhole covers are heavy, being round makes them easier to move from place to place (just roll them!). As an added benefit, workers don’t need to line up the covers with any angles, making round covers easy to slip into place.

但也许是最大的原因，井盖是圆是圆井盖无法通过圆形开口落下。“对于所有孔，有一个‘唇部’围绕孔的边缘，阻碍了盖，这意味着潜在的孔是比盖较小，” Scheckel写入。“一个圆形井盖无法通过其圆形开口下降，因为无论你怎么定位它，盖比孔宽。但一个正方形，如果它是斜着插入孔中，”这将是眛行人和司机都坏消息长方形或椭圆形井盖可能里钻

Results (Chinese) 2:

箭头
大问题
为什么人孔盖是圆的？
由艾琳麦卡锡一月7， 2015
iStock
ISTOCK
如果你习惯在走路时俯视你的脚，你可能已经注意到，大多数人孔，它们的封面都是圆的。或者，也许你参加了一个工作面试，你未来的雇主问了这个问题（这显然已经足够了，它被包括在《完全白痴的工作面试指南》的第三版中）。他想知道你思考的能力，对正确答案不感兴趣，但这是一个很好的问题。在人孔的所有潜在形状中，为什么选择圆？

拉里·斯切克在他的著作《问一个科学老师：关于日常的东西如何真正起作用的250个问题的答案》中说，有很多原因。人孔是圆的，因为"它是抵抗地球周围压缩的最佳形状"。圆形比方形或矩形形状更容易制造，而且由于井盖很重，因此圆形更容易从一个地方移动到一个地方（只需滚动它们！作为额外的好处，工人不需要用任何角度排列盖，使圆形盖容易滑入到位。

但是，井盖是圆的，也许最大的原因是圆形盖不能通过圆形开口。Scheckel 写道："对于所有检修孔，孔的边缘周围都有一个'唇'，它固定了盖子，这意味着底孔比盖子小。"圆形人孔盖不能穿过圆形开口，因为无论您如何定位，盖都比孔宽。但是，如果将方形、矩形或椭圆形人孔盖对角线插入孔中，可能会掉落，"这对不注意的行人和司机来说，都将是坏消息。

Results (Chinese) 3:

箭头
重大问题
为什么井盖是圆的？
作者：ERIN MCCARTHY，2015年1月7日
伊斯托克
伊斯托克
如果你习惯走路时低头看脚，你可能已经注意到大多数检修孔和它们的盖子都是圆的。或者你曾经在一次面试中，你的潜在雇主问过这个问题（很明显，这个问题已经出现在《白痴求职指南》第三版了）。他想知道你站起来思考的能力，对正确答案不太感兴趣，但这是个好问题。在所有可能的检修孔形状中，为什么选择圆形？
根据拉里·谢克尔在他的书《问一位科学老师：250个问题的答案》中的说法，有很多原因。检修孔之所以是圆的，是因为“它是抵抗周围土壤压力的最佳形状”。圆的形状比正方形或长方形更容易制造，而且由于检修孔盖很重，因此圆的形状使它们更容易从一个地方移动到另一个地方（只需滚动它们！）。作为额外的好处，工人不需要把任何角度的盖子排成一行，使圆形的盖子很容易滑入到位。
但井盖之所以是圆的，最大的原因可能是圆的井盖不能从圆形的开口处掉下来。Scheckel写道：“对于所有的检修孔，在孔的边缘都有一个‘唇’支撑着盖子，这意味着下面的孔比盖子小。”。“圆形人孔盖不能从圆形开口处掉下来，因为无论你如何定位，孔盖都比孔宽。但是，如果将方形、矩形或椭圆形的井盖斜插入井中，井盖可能会掉进去，“这对不显眼的行人和司机来说都是个坏消息。