A bicycle is a simple machine that helps you travel faster than walking. It has two wheels, a frame, pedals, and a chain. When you push the pedals, they turn a gear called a chainring. The chainring moves a chain, which turns the back wheel. This pushes the bike forward. The frame holds everything together and supports your weight. The seat lets you sit while you ride. Bicycles are fun and good for the environment because they do not use fuel. Most bikes have gears to make riding easier. Gears are different sized sprockets on the back wheel and the chainring.

When you shift to a small gear, the chain moves to a small sprocket. This makes the wheel spin more times for each pedal turn, so you go faster on flat ground. A large gear makes pedalling easier uphill because the wheel turns less. You change gears using levers on the handlebars. This lets you match your effort to the road. Brakes help you stop safely. On a typical bike, you squeeze brake levers on the handlebars. These levers pull cables that squeeze rubber brake pads against the wheel rims.

The pads rub the rims and slow the wheel down. Some bikes have disc brakes, which work like car brakes. Steering is done by turning the handlebars. The handlebars are attached to a fork that holds the front wheel. When you turn left or right, the front wheel points that way, and the bike follows. Riding a bike uses balance and simple physics. When you pedal forward, you push the ground backwards with the tyres. The ground pushes back, moving you forward. This is Newton's third law. To balance, you lean slightly and keep moving. A moving bike is stable because the wheels act like gyroscopes. When you brake, friction between the pads and rims turns motion into heat, slowing you down. Bicycles are a clever way to use your own energy to get around.

This makes the wheel spin more times for each pedal turn, so you go faster on flat ground.