Wenru Zhang
Practice Two
A. Identify three (3) excellent reasons why manhole covers are round. (The
fact that manhole covers are round so that they can t into round
manholes does not count.) Provide three different reasons and cite a
different Internet reference for each reason. That means that each reason
will have to come from a di!erent source.
One of the reasons why manhole covers are around is for safety
reasons. Round manholes won’t fall into the center of the manhole
not even if is pushed in by accident. On the contrary square manhole
will for sure and easily fall into its hole causing serious accidents.
The second reason why manhole cover is round because is
more cheaper. A round manhole cover has a smaller surface than a
square one, so less material is needed to cast the manhole cover,
meaning lower cost.
The third reason is the convenience of alignment. Circular
covers do not need to be rotated to align with the manhole.
B. Research these questions about tornadoes:
