The physics of a bicycle.

　　The principle of a bicycle is the same as that of a gyroscope.

　　1. Application of measurement.

　　When measuring the length of a runway, use a bicycle. The diameter of the ordinary wheel is 0.71 meters or 0.66 meters. Then the circle length is the diameter by PI, which is about 2.33 meters or 2.07 meters. Then, let the car roll along the track and record the number of rolls. The runway length is 2.33n meters or 2.07n meters.

　　2. The use of force and motion.

　　The decrease of the number and the increase of friction. The front axle, shaft and rear axle of the car are rolled to reduce friction. To further reduce friction, people often lubricate these areas. There are uneven patterns to increase friction. While braking, the hand clenches the brake tightly and increases the pressure on the steel ring to stop the wheel rolling.

　　The reduction of the spring. The seat cushion under the car has many springs, which use its cushioning to reduce vibration.

　　3. Application of pressure knowledge.

　　The bicycle tyre has a bearing capacity. If the car is overloaded, the tyre is crushed by too much pressure.

　　It can increase the contact area between the seat cushion and the body to reduce the pressure on the buttocks, making it easy to get tired by cycling.

　　4. The application of simple mechanical knowledge.

　　The brake in the bicycle brake system is a labor-saving lever with the connecting rod, which can increase the pull on the brake leather. To save energy or distance, the bike also USES a wheel shaft: pedals and sprockets; Rear wheel and flywheel and faucet and rotating shaft, etc.

　　5. The application of knowledge of work and mechanical energy.

　　According to the principle of work: the labor force must be the distance. As a result, people often ride the "s" route on the ascent.

　　The transformation of the kinetic energy and the gravitational potential energy. It is easy to go up a few times before riding up a hill, where kinetic energy is converted into potential energy. And cycling downhill, without the pedal, the speed is faster and faster, this is the potential energy conversion to kinetic energy.

　　On the whole, the bicycle is a laborious machine. It is generally used to save distance to ride a bicycle. Riding the wind is harder than the wind, because the force of the ride is "blown up".

　　6. Precursor and rear drive.

　　The bicycle belongs to the rear drive, which is the rear wheel drive and the front wheel is passive.

　　After the bike is driven by the back drive, a straight, straight line of tire marks, a rule bent, straight for the rear tire mark, bent for the front tire mark.

　　Knowledge of friction

　　Why should the bicycle tyre have uneven pattern?

　　The magnitude of the friction is related to two factors: the size of the pressure, the roughness of the contact surface. The greater the pressure, the greater the friction; The rougher the contact surface, the greater the friction. The bicycle tyre has an uneven pattern, which increases the friction by increasing the roughness between the bike and the ground. The purpose is to prevent the bicycle from slipping.

　　After the brake, why did the bicycle stop?

　　When the brakes are on, the friction between the brake and the car will prevent the rear wheels from turning. The greater the pressure of the hand, the greater the pressure on the brake, and the greater the friction, the slower the rear wheel turns. If brake completely dead, then the rear wheels becomes the friction between sliding friction with the ground (originally to rolling friction, forward direction), backward direction, hindered the movement of the bicycle, so stop.

　　Where does the bike have steel balls? Why steel balls?

　　In the front axle of the bicycle, the shaft, the rear axle, the turning of the car, the pedal rotation, and so on, there are steel beads.

　　People always want to ride a bicycle with ease, flexibility and effort. Rolling instead of sliding can greatly reduce friction, so steel balls are installed where the bike is rotated. You can often lubricate the contact surface so that the friction becomes smaller.

　　The relevant knowledge

　　The lever on the bike.

　　A, the front wheel steering control lever: bicycle handlebar, is efficient to leverage, people can turn the bicycle with A small force, to control the movement direction of the bike and the balance of the bike.

　　B. Lever of brake lever: the brake on the handlebar is the lever of saving force, and people with very little force can make the brake handle with greater pressure on the steel ring of the wheel.

　　The wheel axle on the bicycle.

　　A. Pedal and disk gears on the central axis: make up the energy wheel shaft (the pedal radius is larger than the disk gear radius).

　　B. The bicycle handle and the front fork shaft: make up the energy wheel shaft (the radius of the rotation is greater than the radius of the front fork shaft).

　　C. Gear and rear wheels on the rear axle: make up the arduous wheel shaft (the gear radius is less than the rear wheel radius).

　　Knowledge of air pressure on bicycles.

　　Bicycle tyre inflation: the early variety of wheels are wooden, iron wheel, bumpy. The modern bicycle USES the inflatable inner tube, which mainly causes the pressure increase in the tire to act as a buffer, while reducing the resistance of the bicycle forward.

　　The action of the valve core: the air door core on the inner tube of the inflatable inner tube, the function of the one-way valve, only let the gas enter, do not let the gas leak out, facilitate the air intake, and ensure the airtight inner tube seal.

　　4. Optical knowledge on bicycles.

　　Red tail lights on the bicycle, unable to shine, but at night it can alert the driver, because the bicycle tail light is made up of a number of cellular small room, and every little chamber is consisting of about 90 ° three reflective surface. In the evening, after the car's light hits the bike's taillight, it produces reflected light, which can attract the driver's attention.

　　5. Matters needing attention on cycling:

　　Be prepared with the necessary equipment: helmet, cycling pants, riding gloves, glasses, scarves or masks.

　　There are at least two people walking together. This will ensure both safety and company.

　　The car has no problem with the quality of the car. With a set of hexagon wrench, a wrench is enough. The key is to pick up the tire. You also need glue. Practice it yourself. Also bring water 'food, knee pads.