How bicycles works?

Answer 1

A bicycle is one of the most efficient forms of transport. It works with pedals, which are connected via a chain to the back wheel. The rotation of the pedals moves the chain across gears on the rear wheel, rotating it. To change the gear ratio, the chain is moved to different sized gears of the wheel. The steering works by rotating the front wheel using the handle bars, reorienting the bicycle in a different direction. The brakes work with cables, pulling two rubber plates against the wheel. Newer models have circular plates, which lock onto the spokes of the wheel. This prevents the rubber from being worn down, and is more efficient.

Manpower.

Bicycle uses mechanical energy. It takes the principle of axle and chain. When we paddle, the chain rotates the axle and the wheel also revolves.
The pedals on a bike are connected to a gear that turns the chain. The chain is also connected to a gear that is attached to, and therefore turns, the rear wheel. The rear gears are set up so that when turning forward the will turn the wheel but when turning backward or not moving at all the gears have no effect on the wheel. Different gears are used to gain more speed - a larger gear at the front means the smaller gear at the back will turn faster.
bicycles work through a series of gears and pulleys that move when you petal your petals. When they move the gears and pulleys move thus making the wheels move, propelling you forward so long as you're balanced. that is how a bicycle works.