I. Mechanics
1, the chassis of the car are larger in mass, so as to reduce the center of gravity of the car and increase the stability of the car when driving.
2, the body of the car is designed into a streamlined shape, in order to reduce the resistance of the car driving
3, the car forward momentum - the friction of the ground on the active wheels (active and driven wheels and the ground friction in the opposite direction)
4, the car in the flat and straight roadway at a constant speed forward -- traction and resistance to balance each other, the car by gravity and the ground support force balance
5, the car corner: ① the driver to hit the steering wheel -- force is to change the cause of the object's state of motion; ② the passenger will be tipped in the opposite direction of the turn -- due to passenger inertia
6, the car brakes sharply (deceleration), ① driver to step on the brakes -- force is the reason for changing the state of motion of the object; ② passengers will be tilted in the direction of the car - - inertia ; ③ driver with a small force can brake the car - the principle of leverage ; ④ hard on the brakes - increase pressure to increase friction ; ⑤ emergency braking, the friction between the wheels and the ground from rolling to friction into sliding friction
7. There are also differences in the size and number of wheels of cars for different purposes - this is related to the amount of pressure the car exerts on the road surface
8. The seats of a car are designed to be both wide and large, which reduces the pressure on the rider and makes it comfortable to ride
9. When a car is moving fast, a low air pressure is formed at the The tail will form a low-pressure area, which is often seen in the movement of the car tail dust rolled up to form the reason
10, the traffic management department requires: ① the driver of the car and the front passenger must be fastened with a seatbelt - so that you can prevent the hazards of inertia; ② prohibit overloading of the vehicle -- not only reduce the damage to the road surface of the vehicle, as well as reducing friction, inertia, etc.; ③ prohibited vehicles speeding -- to prevent emergency braking, due to the reaction distance and braking distance is too long and cause a car accident
11, the application of simple machinery: ① steering wheel, wheel, window cranks Wheels, window cranks, etc. are axles, ② speed lever, automatic door opening and closing device is a lever
12, the car climbing a slope to low speed: by P = Fv, power must be, reduce the speed, you can increase traction
13, on the speed of the journey, the calculation of time; reference and the state of the movement of the description of the problem
14, speed limit, mileage, no-beeping signs, to understand the speed limit, the speed limit, the mileage, and so on. Prohibit signage, understand its meaning
Two, acoustics
1, car horns should be loud, the engine sound should be eliminated as much as possible (engine assembly muffler) - this is the source of the sound to reduce the noise
2, in order to mitigate the impact of the noise of the vehicle on the residents alongside the road. Setting up barriers or planting trees next to the road - can attenuate the noise in the process of propagation
3, the horn sound: electrical energy - mechanical energy
Three, thermal
1, car engines commonly used diesel or gasoline engine --they are internal combustion engines--using internal energy to do work
2, the engine is equipped with a water jacket outside, with circulating water to help the engine dissipate heat--water has a large specific heat capacity< /p>
3, winter, in order to prevent freezing bad tank, the night to drain the tank of water - to prevent the hazards of thermal expansion and contraction
4, the car's rear window glass panels embedded in a channel of electric wire - it can prevent the formation of fog inside the car Attached to the glass and condensation
5, just sat in the car or a car driving past you, you will smell the strong smell of gasoline - diffusion phenomenon
6, air-conditioned car window glass is designed as a double - to prevent the transfer of heat
7, environmentally friendly cars use gas fuel, can reduce the pollution of the atmosphere
Four, electrical
1, the car's engine is commonly used in low-voltage motor starting: motor is based on the role of the magnetic field on the current of the rationale for the work of the motor is made, the conversion of electrical energy into mechanical energy.
2, the car motor (car motor) commonly used car battery (battery) power supply, the car can be used during the operation of the wheels to drive the car generator to generate electricity to charge the battery. To the battery charging, electrical energy into chemical energy stored, this time the battery is an electrical appliance; with the battery to the motor power supply, chemical energy into electrical energy, this time the battery is the power supply
3, car batteries are also used for the car fitted with air conditioning, fans, recorders, CD players and a variety of uses for the power supply of lamps, the convenience of the electrical energy into mechanical energy, sound, light and so on
3, the car batteries are also used for the car with air conditioning, fans, recorders, CD players and a variety of uses for power supply, convenient electrical energy into mechanical energy, sound, light and so on
3, tanker trucks usually hang a chain on the tail straight to the road, which is conducive to the transportation process due to the bumps generated by the charge quickly to the ground, to avoid disaster due to electrostatic discharge
4, lights emitting light: electrical energy - light energy
V. Optical
1, the viewer of the car next to the car, the electric fan, recorders, CDs, and various uses of electric lights. p>1, the car next to the rearview mirror, the intersection of the observation mirror are convex mirrors, you can broaden the field of view
2, the car driving at night, the car is generally not turned on, which prevents the car passengers in front of the driver's windshield imaging, interference with the driver's correct judgment
3, the car in front of the windshield is usually not upright (except for the chassis of the car is tall), because the windshield is equivalent to a flat mirror in the car, the windshield is the equivalent of a flat mirror, the windshield is the equivalent of a flat mirror, the windshield is the equivalent of a flat mirror in the car. The windshield is equivalent to a plane mirror inside the car objects are easy to image through it in front of the driver, affecting the driver's judgment
4, the car taillight lampshade: Angle Reflector can be shot back to the light, to ensure the safety of the vehicle behind
5, the car headlamps: concave mirror reflection principle, the near light filament in the vicinity of the focal point, the far light filament in the focal point
Bicycle Physics
Physical knowledge
You know that the bicycle /p>
Do you know what physics knowledge on a bicycle? Let's take a look below.
1.Knowledge of friction on a bicycle.
①Why the outer tires of bicycles have bumpy patterns
The amount of friction is related to two factors: the amount of pressure and the roughness of the contact surface. The greater the pressure, the greater the friction; the rougher the contact surface, the greater the friction. The outer tire of a bicycle has a bumpy pattern, which is designed to increase friction by increasing the roughness between the bicycle and the ground, and its purpose is to prevent the bicycle from slipping.
②Why does a bicycle move forward?
When we ride on a bicycle, there is friction between the bicycle and the road because there is pressure on the ground from the person and the bicycle, and there is no smoothness between the tires and the ground, but why does the bicycle move forward? It still relies on the friction between the rear wheel and the ground, and the direction of this friction is forward. So what does the friction on the front wheel do? It impedes the motion of the bike! Its direction is opposite to the forward direction of the bike. It is these two forces that are equal in magnitude and opposite in direction, so the bicycle moves at a constant speed. However, when one pushes the bicycle forward on the ground, the friction forces on both the front and rear wheels are directed backwards. So who balances these two forces? The friction of the foot against the ground goes forward!
3) Why does the bike stop after braking?
When you brake, the friction between the brake shoes and the rim prevents the rear wheel from turning. The greater the hand pressure, the greater the pressure of the brake shoes on the rim, and the greater the friction generated, the slower the rear wheel will rotate. If the brakes are fully applied, then the friction between the rear wheel and the ground becomes sliding friction (originally rolling friction, in the forward direction), in the backward direction, impeding the movement of the bike, and so it stops.
④Where are the steel balls installed on the bicycle? Why?
Steel balls are installed in the front, center, and rear axles of bicycles, where the handlebars turn, and where the pedals turn.
People always want to ride bicycles easily, flexibly and with less effort. And rolling instead of sliding can greatly reduce the friction, so to install steel balls in the bicycle rotation, we can often add lubricant, so that the contact surface away from each other, so that the friction can become smaller.
2. Knowledge of levers and axles on bicycles.
①Leverages on a bicycle
A, the lever that controls the steering of the front wheel: the handlebar of a bicycle, is a labor-saving lever, people can turn the front wheel of a bicycle with a very small force to control the direction of the bicycle's movement and the balance of the bicycle.
B, the lever that controls the brake brake: the handlebars of the bicycle, which are labor-saving levers, one can use a small force to make the brake press against the steel rim of the wheel with a large pressure.
②The axle on a bicycle
A, the footpegs and the disk gear on the center axle: they form the force-saving axle (the radius of the footpegs is greater than the radius of the disk gear).
B, bicycle handlebar and fork axle: form a labor-saving wheel axle (the radius of rotation of the handlebar is greater than the radius of the fork axle).
C, the gear on the rear axle and the rear wheel: forming a labor-saving wheel axle (the radius of the gear is less than the radius of the rear wheel).
3. Knowledge of air pressure on a bicycle.
Inflatable inner tubes on bicycles: the early variety of wheels were wooden and iron and bumpy. Modern bicycles use inflatable inner tubes mainly to increase the pressure inside the tire, which can play the role of cushioning, and at the same time can reduce the resistance of the bicycle to move forward.
The role of the valve core: the valve core on the inflatable inner tube plays the role of a one-way valve, which only lets the gas in and does not allow the gas to leak out, which facilitates air intake and ensures the sealing of the inner tube.
4, optical knowledge on the bike.
The red taillight on the bike, can not shine on its own, but at night can remind the driver to pay attention, because the bike taillight is composed of a lot of honeycomb-shaped "chamber", and each "chamber" is composed of three about 90 degrees of the Each "chamber" is made up of three reflective surfaces at about 90 degrees. In this way, at night, when the lights of the car behind the bicycle tail light, will produce reflected light, because the red color is striking, can attract the attention of the driver.
The bicycle is a very popular means of transportation in China. In its "body" used a lot of mechanical knowledge
1. Measurement in the application
In the measurement of the length of the runway, you can use the bicycle. If the diameter of an ordinary wheel is 0.71 meters or 0.66 meters. Then the length of one turn is the diameter multiplied by the circumference π, which is about 2.23 m or 2.07 m. Then, let the car roll along the runway, and note down the number of turns rolled, n, then the runway is n × 2.23 m or n × 2.07 m long.
2. Applications of force and motion
(1) Reducing and increasing friction.
The front, center and rear axles of a car are rolled to reduce friction. In order to reduce friction even further, people often add lubricants to these parts.
Many parts are carved with uneven patterns to increase friction. Such as the car's outer tires, handlebar plastic covers, stirrup covers, gate handle covers. Change rolling friction to sliding friction to increase friction. Such as in the brake, the wheel is no longer rolling, and sliding on the ground, the friction greatly increased, so the car can be quickly stopped. At the same time in the brake, the hand hard to grip the brake handle, increase the pressure of the brake skin on the steel ring to achieve the purpose of stopping the wheel rolling.
(2) Spring damping effect.
There are many springs under the seat cushion of the car, which are utilized to reduce vibration by its buffering effect.
3. Application of knowledge of pressure
(1) The weight of a bicycle is engraved on the tire. If the load is too heavy, the tire will be crushed by too much pressure.
(2) The saddle-shaped saddle can increase the contact area between the saddle and the human body to reduce the pressure on the buttocks, so that people are not easy to feel fatigue on the bike.
4. Application of simple mechanical knowledge
Bicycle braking system in the brake handle and linkage is a labor-saving lever, can increase the tension on the brake pads. Bicycles also use axles in order to save force or distance: pedal boards and sprocket tooth plate; rear wheel and flywheel and tap and spindle.
5. Use of knowledge of work and mechanical energy
(1) According to the principle of work: to save energy must cost distance. This is why people often ride "S-shaped" routes when going uphill.
(2) Kinetic energy and gravitational potential energy are transformed into each other.
Such as cycling uphill, people often have to step up a few times, it is easy to go up some, here is the kinetic energy into potential energy. And cycling downhill, without pedaling, the car speed is getting faster and faster, this is the conversion of potential energy into kinetic energy.