Why is there no wind when accelerating in the back of the bus, but there is wind when braking???????

When the bus is moving, the air will flow against the surface of the bus. When the bus accelerates, a negative pressure is formed at the rear of the car, that is, the air behind the car is forward with respect to the car, while on the front and sides of the car, the air is backward with respect to the car. This creates a gust of wind that blows across the surface of the bus, which is why there is no wind when the rear of the bus accelerates.

When the bus brakes, negative pressure is not formed at the rear of the car, on the contrary, positive pressure is formed at the back and sides of the bus, that is, the air flows in the direction of the inside of the bus. This creates a gust of wind that blows across the surface of the car, which is why there is wind when braking.

To put it simply, during the driving of the bus, due to the shape and speed of the bus, a pressure distribution will be formed on the surface of the bus. When the car accelerates, the pressure distribution allows air to flow against the surface of the car, while when the car brakes, the pressure distribution changes, allowing air to blow across the surface.

When a bus travels at a constant speed and accelerates, an area of low air pressure appears behind the rear of the bus, which causes some of the air behind the vehicle to move forward with the vehicle. When the bus brakes, the air that moves with the body continues to move forward due to inertia, and the body is not well sealed, or you open the window at the time, so you feel "windy". To sum up this phenomenon in a popular phrase, it is, "pulling the wind".

Then here it is.

First of all, the faster the flow rate of the fluid, the less pressure on the surrounding (not in the direction of its flow), because the wind speed around the car body is large and the pressure is small when accelerating, and the wind formed by the wind flows through the surface of the car body, that is, without the help of external force, the air does not flow from the low air pressure (that is, outside the car when accelerating) to the place with high air pressure (that is, inside the car at this time).

When braking (i.e., the car accelerates backwards) in the opposite direction, the phenomenon is reversed.

The air pressure outside the acceleration --- --- small.

The air pressure outside the deceleration --- --- to the inside.

In fact, the power of leaning back comes from yourself. When the car slows down, you lean forward due to inertia, and your body instinctively resists this forward leaning. When the car stops, the inertial force is gone, but your muscles are still tense, and the person leans back.

You can try to use the front seat against your body when the car brakes, and relax your whole body, and this tendency to lean back will be greatly reduced.

Before, people were moving forward with buses. When the bus brakes suddenly, the person is still moving forward due to inertia, so the person rushes forward.

Law of Inertia).

Large vehicles use air compressor brakes, and the car has an air pump that generally exhausts at 10 kg atmosphere, and there is an exhaust valve that can be adjusted.

It is the sound of air pressure reflux when the brakes are relaxed.

The stinging of the nose is due to the sensitivity of the nasal mucosa, which is generally a symptom caused by cold viruses, and the symptomatic medicine is "fast-acting cold and flu capsules" and "breathamine" that can improve the symptoms of nasal sensitivity, and at the same time, "banlangen" has antiviral effects and can promote the resolution of colds.

2AT based on x=vot+1 macro

Solve t1=1s x1=9m and t2=2s x2=7m to get a=-2m s vo=10m s

Then, according to v=v0+at

Bring v=0 a=-2m s into the leather and transport t=5s, that is to say, after 5s, the car stops and grips are changed.

That is, the displacement of 6s and 5s is the same.

Bring 5s to x=vot+1 2at

x=25m

Dear, give a little branch no

v=v0-at=20-4×3=8m/s

v=ata=v imitation a=20 4=5s

2011-8-6 21:01:26Meow Meow sauce Bo and the big stupid guest to accompany.

It is suspected that the exhaust valve of the pneumatic sub-pump is damaged or blocked, resulting in the high-pressure gas in the sub-pump not being able to quickly drop to atmospheric pressure, resulting in brake lag; You can let a person step on the brakes in the car, you listen below, generally the exhaust sound is very crisp after releasing the brake, if there is a slight exhaust sound in a short time after releasing the brake, it is the above reason; The brake adjustment arm and lever should also be checked.