Manholes in general, at least in North America are designed in circular shapes for many reasons. Here is a list of reasons for the circular shape:
- A round manhole cover cannot fall through its circular opening, whereas a square manhole cover may fall in if it were inserted diagonally in the hole. (A Reuleaux triangle or other curve of constant width would also serve this purpose, but round covers are much easier to manufacture. The existence of a “lip” holding up the lid means that the underlying hole is smaller than the cover, so that other shapes might suffice.)
- Round tubes are the strongest and most material-efficient shape against the compression of the earth around them, and so it is natural that the cover of a round tube assume a circular shape.
- Similarly, it’s easier to dig a circular hole and thus the cover is also circular.
- The bearing surfaces of manhole frames and covers are machined to assure flatness and prevent them from becoming dislodged by traffic. Round castings are much easier to machine using a lathe.
- Circular covers do not need to be rotated to align them when covering a circular manhole.
- Human beings have a roughly circular cross-section.
- A round manhole cover can be more easily moved by being rolled.
- Tradition.
- Supply. Most manhole covers are made by a few large companies. A different shape would have to be custom made.
http://en.wikipedia.org/wiki/Maintenance_cover#Circular_shape
Here is the last question of the month. The winners in differen categories will be announced on may 7.
Thank you everyone for taking part in problem of the day. Look for more problems in the future.
Every time you walk on streets or sidewalks you come across these metal coverings that are mostly in circular shape. These are called Manholes. A manhole (alternatively utility hole, maintenance hole, inspection chamber or access chamber) is the top opening to an underground utility vault used to house an access point for making connections or performing maintenance on underground and buried public utility and other services including sewers, telephone, electricity, storm drains and gas.
Why are manholes in circular shape?
The active ingredient in peppers that is responsible for heat production is a chemical known as Capsaicin. The scientific name for this chemical is 8-methyl-N-vanillyl-6-nonenamide
Here is another kitchen chemistry problem:
Hot peppers are delicacies that are enjoyed by many cultures around the world. Chili peppers have been a part of the human diet in the Americas since at least 7500 BC. Hot peppers produce a lot of heat when consumed. The heat from peppers comes from certain chemical. What is this chemical?
(a b c) + ( a c) = 3 a 0
a, b, and c are digits, and . b > 0. ab represent 29.
Here is a math challange.
(a b c) + ( a c) = 3 a 0
a, b, and c are digits, and . b > 0. What numeral would ab represent?
The toilet paper is made from the Cellulose in trees which is a polymer of Glucose.
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. The tides occur with a period of approximately 12 and half hours. Therefore after four hours the number of rungs above water will still remain four.
There are only four more problems left in the month of April to determine the winners.
Today’s problem is testing your knowledge about bathroom chemistry.
Time for toilet paper trivia. It’s made from paper, which comes from the cellulose in trees. Cellulose is polymer of which sugar?
Here is the math problem you have all been waiting for.
A boat is docked, and its ladder is hung. Four of its 13 rungs are above water. The rungs are 1 feet apart. If the tide has begun to go out at a constant rate of 8 inch per hour, after 4 hours how many rungs will be above water?
