Can a person really develop bones of steel by crushing rocks on his chest?

Breaking stones with the chest is a street performance that has existed since ancient times.

It is undeniable that this kind of performance is very attractive, because a big stone is placed on the chest and hit with a hammer, the stone breaks, but the human body is unharmed. This result seems to be very different from our common sense. What's more, a needle board with dense steel needles is placed under the body. After the performance, the performer is not only not crushed by the stone, but also not stabbed by the needle board. For the performance effect, the performer usually interprets this result as "golden bell and iron cloth shirt". So can people really train themselves to be steel bones? Of course not. Because the muscles and bones of the human body are not made of the same elements as steel, and one element cannot be transformed into another element unless nuclear fusion or nuclear fission reaction occurs.

Since people cannot train their bodies to be as strong as steel, how can they break rocks with their chests?

In fact, this performance is not against common sense at all, but strictly abides by the laws of physics. As long as it is operated properly, there will be no injury at all. The matter of breaking a big stone with the chest can be broken down into several different parts. The first part is the interaction between the hammer and the big stone, the second part is the interaction between the big stone and the human body, and the third part is the interaction between the human body and the needle plate. First, let's talk about the first part, why the hammer can break the big stone. In fact, the problem of the first part is very simple. The reason why the hammer can break the big stone is naturally because the force applied by the hammer to the big stone is large enough. So how much force does the hammer apply to the stone? This can be calculated by the momentum theorem. Force is equal to mass multiplied by velocity, divided by the time the force acts.

The mass of the hammer is naturally very large, and the hammer falls very quickly when hitting the rock, so the mass multiplied by the speed is a relatively large number.

The hammer and the rock are both very hard materials. When the hammer hits, the contact between the two is just a matter of a second, so the time of force is very short. Dividing a very large number by a very small number will naturally give a very large result, so the force exerted by the hammer on the rock is very large. On the other hand, pressure. Pressure is equal to force divided by area. We have just calculated that the force of the hammer is very large, but the contact area between the hammer and the rock is very small, so the pressure is also very large. With a large force plus a large pressure, the rock will naturally be broken.

Next, let’s look at the second part. Why didn’t the big rock crush the person to death?

During the whole process of crushing the stone on the chest, the stone never moved, so the momentum of the stone itself was zero, which means that the momentum of the first part is equal to the momentum of the second part. Although the momentum of the two parts is equal, the contact time of the two parts is very different. The sledgehammer and the stone are both hard, so the contact between the two is only a matter of a moment, but the human body is soft, so the process of the stone pressing down will be buffered by the human body. Relatively speaking, the contact time between the stone and the human body is much longer than the contact time between the hammer and the stone. The same force is dispersed over a longer time, and the force per unit time is reduced. On the other hand, there is pressure. Pressure is equal to force divided by area. The contact area between the human body and the stone is very large, and the force per unit time of the human body is relatively small, so the final pressure is much smaller than the first part, and the person will naturally not be crushed.

Now comes the last part, the needle plate.

Let's talk about the force first. The interaction force between the human body and the needle board is actually the same as the second part. There is no need to say more about this. Let's mainly talk about the pressure. You may think that the needle tip is so sharp and the contact area with the human body is so small, so the pressure must be very high. Indeed, if there is only one needle, there is no need for a big stone or a hammer. People will be pierced by going up, but the problem is that there are many needles on the needle board. If you have seen the performance of breaking stones, you will definitely find that there are so many needles on the needle board used in the performance, so dense that you can't count them all in two minutes without using mathematical methods to calculate them, just counting them one by one.

The needle board is densely packed with needles, which looks scary, but is actually very safe.

Because there are too many needles, the total contact area between the needle board and the human body is actually very large. Correspondingly, the pressure between the human body and the needle board is very small, so the human body will naturally not be stabbed by the needle board. If you take a needle board with only 20 needles, no one dares to lie on it. It can be seen that from a physics point of view, breaking stones with the chest is a very common thing. If this can be regarded as a kind of kung fu, then everyone can do this kung fu. However, although this is the case, there are certain skills for everything, and the same is true for breaking stones with the chest. Professional performers need training. We do not have the corresponding skills and have not been trained. It is easy to get injured accidentally if we try rashly.

For more information, please follow the official account: sunmonarch