Engineering & MachinesEngineering Design
Why Manholes Are Round
A round cover can never fall into its own hole
So many of the heavy iron lids in the street are round. Why would a circle beat a square for that job?
You'll find out
- How a square lid falls into its hole
- Why a round lid never can
- The other shape that would work
Why it matters
The idea behind that shape turns up again in coins and drill bits. It all starts with a lid under your feet.
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