2006-07-13 13:29:06 · 8 answers · asked by Anonymous in Science & Mathematics ➔ Other - Science
so the lid won't fall in when removed
2006-07-13 13:32:19 · answer #1 · answered by Anonymous · 8⤊ 4⤋
It has do do with the shape of the object. consider a circle versus another equilateral shape (all sides and angles equal).
A circle has a single radius. IE if you draw a line from the exact middle to the outermost point in any direction you always get the same number. Whereas if you take say a square or a triangle and draw a line perpendicular to a side you get a much shorter line that drawing one from the center to bisect one of the vertices (corners). What this means is that for any shape other than a circle, if you drop it with the shortest portion parallel to the ground through the manhole parallel to the line from the middle of the hole to the vertex, the manhole covers shortest point may be small enough to fit through the widest part of the hole and fall and flatten the worker. A circular mahnole cover does not have this drawback. Sinec all lengths are the same there is no difference between the widest and narrowest part of the manhole cover, thus the hole it fits over can be made a few inches smaller in diameter and the cover will NEVER fall through the hole. EVER. Unless the hole is widened or the covered gets shrunk.
And most places tend to not like the idea of their utility workers being killed on the job. Insurance is a B---- ... AD thing... *wink*
2006-07-13 20:38:42 · answer #2 · answered by Michael Gmirkin 3 · 0⤊ 0⤋
If they were square, the lids might fall into the holes and since they weigh about 90 pounds, it would take 2 or 3 strong men to lift them back out again. They are round so they won't fall into the hole they are covering.
2006-07-13 20:33:27 · answer #3 · answered by correrafan 7 · 0⤊ 0⤋
They are round because any other shape other than round will allow the lid to fall into the hole.
BTW not all man hole lids are round. There are some that are rectangle. They have a safety bar in them to prevent them from falling into the hole.
2006-07-13 20:34:19 · answer #4 · answered by fiestyredhead 6 · 0⤊ 0⤋
First off, it maximizes area for a given radius and secondly it's the ony shape that can't fall through a slightly smaller version of itself. Trust me, I did the math for it once. Also, you wouldn't have to rotate the lid to make it fit right.
2006-07-13 20:34:09 · answer #5 · answered by Nick N 3 · 0⤊ 0⤋
cause most men working on man holes are round as hell
2006-07-13 20:32:31 · answer #6 · answered by The King 6 · 0⤊ 0⤋
True answer: Because with a little flange around their edges, there is no way for it fall into the hole they cover.
Clever, huh?
2006-07-13 20:34:24 · answer #7 · answered by stevenB 4 · 0⤊ 0⤋
Hi, oops !! I was looking for the washroom !
2006-07-14 00:17:21 · answer #8 · answered by Anonymous · 0⤊ 0⤋