Will coins falling from skyscrapers kill people?

Can coins falling from skyscrapers really kill people?

Louis Bloomfield, an American physics professor, has done experiments to prove that

Will coins falling from skyscrapers kill people?

Can coins falling from skyscrapers really kill people?

Louis Bloomfield, an American physics professor, has done experiments to prove that coins falling from the sky are not so terrible. But my personal opinion is that it will kill people, but it will only be a small probability event. & amp#8205;

? Under what circumstances can coins kill people?

Why do I hold this view? This is because the hard disk is small, but it falls fast, hitting the vital parts of the human body, such as the temples, and it can still kill people. Or when the victim has physical defects, fatal events may also occur.

The temple is in front of the auricle, on both sides of the forehead and above the extension line of the outer corner of the eye. Temples are called "strange points outside meridians" in the study of meridians in traditional Chinese medicine, and they are also one of the "dead points" that were first listed as key parts by various martial arts boxing scores. It is recorded in Shaolin Boxing that once the temple is clicked, "it will faint lightly, but it will be fatal". Modern medicine has proved that hitting the temple can cause death or concussion, making people unconscious.

The position of the temple is the junction of several skulls, called the pterion, which is easy to fracture. At the same time, there is an anterior branch of the middle meningeal artery in the skull at the pterion. Once the skull at the pterion is fractured, it is easy to cause artery rupture, forming intracranial hematoma and death.

Of course, you may still doubt my opinion, but do you believe that hail will kill people? Do you believe that throwing peas at people will kill people? Of course, this is possible. The pea hit the victim's temple impartially and the victim died on the spot. Do you believe that one punch can kill people? Of course, this can happen, for example, the victim has a head injury. For example, if a bullet hits a person, do you think it will be fatal? The answer is no, the bullet must also hit the vital part of the person to cause death.

What's your point of view that you can't die?

Due to air resistance, coins fall at a limited speed and cannot be fatal. Of course, physicists are right about air resistance. For example, the effective range of rifle bullets is 1500m, and the maximum range is 2400m. However, when it exceeds the effective range, the damage will naturally weaken due to the influence of air resistance, wind speed and self-weight.

How much resistance will coins fall?

Take the RMB one-dollar coin as an example. The shape of the coin is a cylinder, but it is a cylinder with a height of only 2mm. When it falls from a height, it will have a different trajectory if there is no air resistance. The first is that the edge of the coin falls vertically downward; The second is the positive, negative, downward and vertical downward of coins; The former encountered little resistance, while the latter encountered great resistance.

The real situation is that when a coin falls, it will roll in the air under the action of wind resistance. So how much resistance will coins falling from skyscrapers encounter at the bottom of the road, and how fast will the bottom of the road go?

The formula of air resistance at high speed is as follows:

Where ρ is the density of air; C d is the resistance coefficient, which is very dependent on the shape of the object; A is the cross-sectional area of the object, and v is the velocity of the object relative to the air.

We still refer to the calculation conditions in the experiment:

Take 1 yuan coin as an example: the mass is about 6.3g, the diameter D is about 25mm, and the thickness H is about 2mm. Usually the air density ρ at temperature and pressure is 1.2 kg/ m 3, so we assume it is constant. When the coin falls horizontally, the resistance coefficient Cd is 1. 15. When the coin falls vertically, there is no exact data to query, but it is also around 1. Substituting these specific values, we can calculate the closing speed of coins when they fall horizontally and vertically as their minimum and maximum values, and get the results:

That is to say, no matter how high the coin falls, the final speed will not exceed 45.4 m/s. In real cases, the coin will roll in the air when it falls, so it can be considered that the closing speed of the coin in real cases is between the above two situations.

The latest research in the United States confirms that the above experiment is not established.

American scientists have proved through experiments that a coin falling from the sky will not kill people.

In the research, Louis bloomfield, a physicist at the University of Virginia, used a wind tunnel to simulate a penny coin falling from the sky, and found that the impact of the coin was very small. Figuratively speaking, it is like a leaf, not a torpedo. The results show that the air resistance and the shape of the coin prevent it from becoming a deadly weapon. The flat surface of the coin increases the air resistance. If you fall from a height of 50 feet (about 15 meters), the free fall speed is only 25 miles per hour (about 40 kilometers per hour), and the person who is hit will not feel any pain. If there is no air, the speed of a penny coin can reach 208 miles per hour (about 334 kilometers per hour), which is enough to cause serious injuries, but it still cannot pierce the skull.

However, if you change coins into ballpoint pens, the situation will be different. Bloomfield pointed out that if a ballpoint pen falls from a tall building in some way, it will easily lead to death. If you fall sideways, the people under the building will be safe. If you fall like an arrow, the speed can reach 200 miles per hour (about 32 1 km per hour), which is enough to pierce sidewalks and boards. He said, "You certainly don't want to be hit by a ballpoint pen falling from the sky."

Broomfield's experiment proved Galileo's law of free fall. The falling speed of an object is not determined by its mass, but by its shape and resistance. As early as16th century, Galileo pointed out that in a vacuum environment, objects with different weights fall at the same speed.

Another set of experiments on parabolic objects at high altitude

The purpose of this real danger is to tell us that throwing objects at high altitude is not dangerous? Obviously, I didn't say that. Let's look at another group of experiments done by Chongqing University, except that the items in the experiment changed from coins to eggs.

High-altitude falling experiment

Experimental equipment: balance, tape measure, transient digital measurement system of collision process, glass jar, plastic basin, 23 eggs (weighing between 60 and 80 grams) and two flat plates with a thickness of about 0.5 cm.

Experimental location: School of Physics, Chongqing University.

Experimenters: Mr. Wu Shichun, director of Mechanical Thermal Laboratory and senior engineer, Yang Xu, a senior majoring in applied physics in School of Physics, Chongqing University, and Qingqing Dance.

Parabolic experiments at high altitude are very dangerous. The higher the altitude, the smaller the target, and it is not easy to succeed. For the sake of safety, we abandoned the high-rise experiment and chose the heights of 8 meters and 1 1 meter. Then go to the lab to do collision experiments. )

Experimental process:

Yesterday morning 1 1: 30, we weighed 23 eggs in the laboratory and recorded their weight. Then I chose a corner of the physics experimental building and set up a cordon. Lock the glass jars, plates and plastic pots on the ground, let the eggs fall freely from different heights, and observe the smashed objects. These items are chosen as targets because they are hard and brittle. )

8 meters high:

After we measured the second floor and a half -8 meters high with a tape measure, Yang Xu and Qingwu stood on it, ready to let the eggs fall freely. Teacher Wu put a plastic basin with a diameter of about 50 cm in their vertical place. "The egg weighs 65.75 grams!" Yang Xu must weigh the eggs before laying them for record.

"3,2, 1, release!" Blink of an eye, Yang Xu loosened the egg. "pa!" The egg soon landed with a muffled sound. Unfortunately, the first egg deviated from the target and hit the ground, and the egg liquid splashed around two or three meters away. Because at the height of 8 meters, the target below has become as small as the fingernail. The egg missed the target twice in a row.

"Come again! The egg weighs 70.35 grams! " Yang Xu reported the finished weight. "hey!" With a loud cry, the egg finally hit the target. This time, the egg liquid did not directly hit the ground and splashed far away, and there was no crack in the target.

After recording the data, we replaced the basin with a ceramic plate with a thickness of about 0.5 cm and a diameter of 35 cm, and buckled the plate on the ground. Because the target area of the plate is too small, I hit it twice and missed it.

"3,2, 1, release!" When Yang Xu dropped the sixth egg from a height of 8 meters, he finally heard a crunchy sound of "pa" and hit the middle of the plate. After inspection, the plate is also intact, without any cracks, and the plate is surrounded by egg liquid.

We always hit the plate with two eggs, weighing 67.74 grams and 7 1.04 grams respectively. When we use a glass jar with a diameter of about 15 cm and a height of about 20 cm to do the experiment, we can't get eggs because the target is too small.

1 1 m high:

Then, we raised the experimental height to the fourth floor of the experimental building, and measured the experimental height as 1 1 m with a tape measure. With the increase of height, it is more and more difficult to hit the ball. Beat three or four eggs in a row, find the feeling and finally hit it.

"69.32 grams!" Yang Xu reported the weight of eggs. When the eggs hit the upside-down plastic basin, the basin still didn't crack. "73.14g!" When the egg hit the inverted ceramic plate, the egg liquid splashed as far as 4 meters around, but the plate did not crack.

"The wall of the board is very thick, and the four sides can help it to bear the force together. Eggshells are not as hard as plates, so they don't crack. " Teacher Wu analyzed.

After the outdoor experiment, in order to get more accurate data, we went to the laboratory and reconstructed it with the transient digital measurement system in the collision process (this system is adopted because it can simulate the instantaneous impact force experiment in the collision process).

Experimental results:

Some data can be obtained from the experimental results in the laboratory. When breaking eggs, the stress area is about 1 cm2, and the stress time is about 5 milliseconds. Then, at a height of 8 meters, an egg weighing 67.74 grams fell vertically, and the force of hitting the plate was about 180 cattle, 34 kilograms; At the height of 1 1 m, 73. 14 grams of eggs fall, and the force borne by the plate is 2 15 cattle, 44 kg.

How badly did the eggs fall from these floors?

Similarly, with more than 70 grams of eggs, Mr. Wu and his classmates measured the force falling from the height of the 4th floor, 8th floor,18th floor and 25th floor.

Falling from the fourth floor: the force is about 2 16 N/cm2, 44 kg, which is equivalent to the weight of a 7-year-old boy.

Falling from the 8th floor: about 304 N/cm2, 62 kg, equivalent to the weight of a boy 10 years old.

Falling from18th floor: about 456 N/cm2, 93 kg, equivalent to the weight of a 14-year-old boy.

Falling from the 25th floor: about 536 N/cm2, about 109 kg, and the stress area is only 1 cm2, which is equivalent to the weight of an adult woman.

"This data is only a conservative calculation, and the actual data is definitely greater than this force." Teacher Wu said that not only the measured data are conservative, but also when throwing objects at high altitude, the thrown objects often have additive power.

Will throwing eggs at tall buildings break people's skulls?

Generally speaking, the hardness of normal adult skull is very large, the thickness is about 0.95~ 1.2 cm, and the endurance limit is 200 ~500 kg. Static weight exceeding 280 kg may lead to fracture.

Teacher Wu said that these data are only theoretical data. After reading these data, you may think that throwing eggs from the 25th floor will not break people's skulls, but you should also consider everyone's own differences and throwing strength.

Orthopedics doctors also said that in addition to the individual differences of each person's skull, even if the same person suffers from osteoporosis due to calcium deficiency, the hardness coefficient will be reduced. Therefore, the problem of how much force the skull can bear depends on the situation, and the variable range is also relatively large. Although throwing eggs from the 20th floor did not reach the limit value of skull fracture in theory, it may be ok to hit some people's heads, and something will go wrong if you change one. Even if it doesn't break the skull, the weight of dozens or hundreds of pounds on the head may cause a concussion.

Conclusion: Injuries caused by throwing objects from high altitude happen from time to time. Please don't let it happen again. The parabolic objects in the sky were either hurt by you or by others.

For everyone's safety, please don't throw objects at high altitude!

Relevant information and pictures are all from the Internet: through Baidu search.

Relevant reference sources are as follows:

China French Open/FLAL/XSAL/XFAL/201001/309412.html.

Computer news/n/2013/0507/c354326-21395904.html

Guo Ke. Com/ Chongqing/201112/02/3381194.html.

Window of Hebei/html/2013/snzx _ 0723/33573.html