Bicycles with external gears have two, one guide pulley and one tension pulley, both in the rear derailleur. Some bicycles have further pulleys on the frame for either the brake or the shifter wire to run over.
pulley
The chain is wrapped around a cogwheel, which could be described as a pulley.
The bicycle is not a simple machine, there are too many interacting moving parts.
pulley
lever at crank, connected by chain to lever at rear wheel
pulley
A bicycle is an example of a complex machine.
A common example of a pulley is a flagpole pulley system, where a rope is used to raise and lower a flag. The pulley helps to reduce the amount of force required to lift the flag by distributing the load.
gears and wheel and axle
The rear derailleur pulley in a bicycle's gear shifting system guides the chain to move smoothly between different gears, allowing the rider to change the resistance and speed of pedaling.
Using an oversize derailleur pulley in a bicycle drivetrain system can reduce friction, improve shifting performance, and increase efficiency by allowing for smoother chain movement and better alignment with the cassette cogs.
No it is not. A belt, for example, goes around a pulley.