Please help me analyze the physics involved in a car rear end collision from a physics point of view

The concept of rear-end collision is actually to follow the back of a moving object in front, which can easily cause accidents. For example, a car rear-end collision is very dangerous. In physics, rear-end collisions use references.

Let's take a car as an example, the rear car is used as a reference, for example, when the speed is the same, the rear car is stationary relative to the front car. At this time, the car in front suddenly braked sharply, and the speed suddenly slowed down to stop, and the car behind did not react at this time, and it collided. The reaction is slow, the brakes are applied late, and there is physical acceleration.

Friction, inertia, etc.! After adding the car to step on the brakes, that is, locking, this friction is the sliding friction between the car wheel and the ground, this force divided by the mass of the car is the acceleration of the car at this time, and the direction and friction are in one direction, that is, backwards. At this time, the displacement of the rear car is s=, note that here a and v.

The direction is reversed, so it's a minus. ） v。is the initial velocity when the brake is applied, t is the time to stop, and a is the acceleration.

At this time, the moment the rear car steps on the brakes, this s is the distance that the rear car stops, when this s" to the distance from the front car to stop (calculated from the place where the rear car steps on the brakes), fortunately there was no accident, but when this S > this distance, congratulations, the accident!

That's mostly it, and the overall use of the reference, friction (static friction.

Sliding friction, rolling friction), inertia, acceleration, displacement, etc.!

Hope it helps the landlord. Word by word!

A car rear-end collision involves knowledge of the following physics:

Uniform linear motion, uniform variable speed linear motion, friction, force analysis, reaction time, displacement relationship and time relationship in the chase and encounter problem, etc.

Acceleration catch-up encounter problem The movement process of two vehicles before they collide.

Conservation of Energy vs Conservation of Momentum Problem The physical process that occurs at the time of collision of two cars.

It also involves inertia, friction, conversion of mechanical energy into internal energy, and so on.

If you don't understand, you can ask.

Inertia, acceleration, velocity, friction, work, power, ......

inertia, the car's headrest can play a protective role.

Hello, the reason for the decrease in the torque of the loss of power brake of Tianji transmission may be that the contact part is stained with moisture or oil and other substances, which will reduce the torque and the braking sensitivity will become worse, or the reason for the decrease in the torque of the loss of power brake is that as long as the brake spring fails and the brake skin is worn.

The reason for the decrease in the torque of the power loss brake is as long as the brake spring fails and the brake skin is worn.

Substances such as water or oil on the contact area will reduce torque and reduce braking sensitivity.

All ghost dreams cannot be easily broken, cannot be understood with modern source thinking, Freud's dream theory is the subconscious, repressed desires, the satisfaction of substitutes (images), metaphors, while the dreams of gods and ghosts are direct and have special meanings.

That's medicine The so-called ghost press is caused by your nerves, you think you're awake, but your nerve centers don't transmit your signals, it's just your sleep consciousness Don't be afraid! There's something for everyone!

There may be something in your life that you are afraid of, but try to overcome it as much as you can, and don't believe in any snake gods.

We know that when the ball is flying in the air, if it not only makes it forward, but also makes it rotate continuously, because the air has a certain stickiness, when the ball rotates, the air will rub against the surface of the ball, and the rotating ball will drive the surrounding air layer to rotate together. If the ball moves in a horizontal direction to the left and rotates clockwise around the axis of the perpendicular paper, the air flow flows to the right with respect to the ball, and the surrounding air circulation, which is also driven by the rotation of the ball, rotates in a clockwise direction. In this way, the velocity of the air above the ball rotates in addition to the translation to the right, and the two directions are the same; Underneath the ball, the translational velocity (to the right) is in the opposite direction to the rotational velocity (to the left), so its resultant velocity is less than the resultant velocity of the air above the ball.

According to Bernoulli's theorem of fluid mechanics, the pressure on the side with greater velocity is smaller than the pressure on the side with less velocity, so the pressure above the ball is less than the pressure below the ball. If the ball rotates quite fast, so that the upward resultant force of the air to the ball is greater than the weight of the ball, then the ball is subject to a vertical upward resultant force in the process of advancing, so that the ball will do a curved motion on one side and one side upwards in the process of horizontal movement to the left, and the ball will turn upward. To make the ball turn left and right, simply rotate the ball around the vertical axis.

It seems that the key is the athlete's footwork at the moment of touching the ball, that is, not only to make the ball forward, but also to make the ball rotate rapidly, different rotation directions, the ball steering is different, which requires the athlete's hard training, in order to practice a set of skillful foot kung fu, only after thousands of tempering, in order to reach the point of perfection.

Where the flow velocity is large, the pressure is small; Where the flow rate is small, the pressure is strong. When the ball spins quickly, the velocity of the air on one side of the ball is greater than the velocity on the other side, so the pressure on one side of the ball is greater than the other, so the ball turns. When kicking the ball with your foot, rub the inside of your foot against the edge of the ball and the ball will spin, the inside of your foot will turn to the left, and the outside of your foot will turn to the right.

You don't need to exert any force, the main thing is to spin quickly when the ball flies out.

Air resistance is not considered here.

The rotation is of course due to the fact that the resultant moment with the center of the sphere as the axis is not 0

Only when the resultant force passes through the center of the ball so that fl=0 and the moment is 0 will not rotate the direction of the resultant moment is the direction in which the ball rotates.

In the presence of air, the ball will deform when it is kicked, so the shape is irregular, and it will arc if it does not rotate, which is not something that can be controlled if you want to control it.

It's not that so many people believe in horoscopes, but the concept of horoscope blood type is the same as fortune telling, ambiguous, and it feels yes and no.

For example, Pisces people always maintain a naïve and loyal temperament, Pisces people are warm, flexible and mysterious and so on, but Pisces people are sometimes at a loss because of cowardice, carelessness, laissez-faire and vague thoughts, and they will also be pessimistic and disappointed because of their silence and lack of unrestrained enthusiasm or something, which is a kind of first praise you how elegant you are, and then tactfully tell you how you may have flaws, so that you can agree with its views in a compliment After that, you will unconsciously and thoughtfully accept the so-called defects.

Actually, it's the same as fortune telling, everyone has similarities and differences, even if your zodiac sign says you're not naïve, it's another way to say you're kind, even if it's brutal, it's about having a personality.

Everybody has their own vanity, they want to be satisfied, and they want to know everything about themselves, such as fate, luck, and emotions.

All of this is fulfilled in the theory of constellation.

Superstitions are harmful, horoscopes are just a kind of entertainment for young people, even if they are.

People who usually believe in these things, when it is critical, if something happens, they will also use scientific methods to solve it, and will not wait for the judgment of the so-called fate, even if it is the so-called fate, but humans are animals who are born to fight against fate. That's why human beings will progress, so there is no destiny, their own way, and they will open up their own path.

It's a kind of mental suggestion and mental decompression.

If a person thinks on the good side, the person's mental state, physiological functions, etc. will be in a good state.

Modern people are stressed, and these are a way to decompress. It's normal.

Mind games can relax the mind, but there is no need to take it seriously. If the constellation says that if it is scientific, then where is its test report? How much does it have to sample, how long does it have to look at to get those results now?

What people believe, mostly influenced by books, fortune tellers, so hard, esoteric. People don't like it anymore, so who reads what books, and what books affect whom.

In fact, there is no scientific and technological foundation, most of them are just a kind of psychological comfort, because they don't know how to solve the problem, or they are too lazy to solve it, and they just want a quick and simple way to deal with the problem. Some people will believe it, it is only a matter of probability at best, and it is not surprising that there are so many people in the world that they have something in common!

You are selfish and haughty! Completely a modern product. At.

There is no theory of relativity, no calculus, no automobiles, etc., the ancient ideas are still admired by modern people, the four famous works are still deeply rooted in the hearts of the people, the connotation of the I Ching is incomparable, and Daji is still obsessed! And divination and the hotel and the spring building are still flourishing since ancient times, which shows that the connection between the three is extraordinary!

1There is no substitute. 2. There are problems to be solved. The 3 zodiac signs are accurate, have a long history, and have a high degree of social identity.

4. Herd mentality. 5 There are very few books on anti-horoscopes. 6. Propaganda of the major **.

The 7 zodiac signs claim that the planet's gravity influences fate, appearing "scientific". 8. There are many people who believe in the constellation to relieve boredom.

I was the second to answer the question.