What’s the difference between a cog and a gear?
In: Engineering
A cog can be any spinning wheel with sticky-outy bits which pushes against another wheel with sticky-outy bits so that they both spin together.
A gear is a special type of this mechanism in which the sticky-outy bits are specially shaped so that at the point where they touch the two pieces *roll* against each other rather than *sliding* against each other, as cogs would do.
Rolling generates less friction than sliding, so this special shape is more efficient at transferring power from one wheel to the other.
This special shape is called an involute.
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