Is the friction force of multiple objects internal force

1.

The price of cryptocurrency bitcoin has continued to rise sharply since the beginning of this year, driven by sufficient liquidity in the global capital market, investors' keen pursuit of risk and corporate and institutional investors' starting to buy. Market analysts believe that bitcoin's surprising rise challenges people's imagination and may indicate abnormal risks in global financial markets

the value of bitcoin will grow by more than 415 billion US dollars in 2021, reaching more than 1 trillion US dollars. In the past six months, bitcoin prices have risen by about 350%. Market participants said that recently, some institutions and large companies said they would enter the field of digital currency, which pushed up the price of bitcoin. Changes in the flow of speculative funds benefiting from the early stage in the future and the attitude of regulators may have an impact on its trend. At the same time, it makes more cryptocurrencies known, but the value of most cryptocurrencies, especially bitcoin, fluctuates every day. Although virtual currency is designed to promote safer transactions, it is not difficult to see that its value is becoming more and more speculative through the recent price fluctuation of bitcoin. Some encryption investors become millionaires overnight, but they may lose most of their wealth in a few weeks. It also shows the huge and unreliable nature of bitcoin, especially the goods and services as a currency

potential problems and risks faced by bitcoin

technological innovation: first of all, the challenge bitcoin will face is technological innovation. While the decentralized design of bitcoin makes us refreshing, it also limits the development of bitcoin. Every upgrade of bitcoin protocol needs to reach a consensus with each node on the network, but everyone has different views on bitcoin, and consensus is often difficult to achieve. This problem leads to the bifurcations of bitcoin and the slow development of bitcoin protocol itself. At the same time, with the development of science and technology, the implementation and application of quantum computing will also break the security model built by bitcoin based on the overall computing power of all nodes in the network, which may theoretically achieve 51% computing power attack. So far, this problem has not been solved. In other words, bitcoin may suddenly become less secure after the advent of quantum computing technology. In addition, e to the consensus mechanism of bitcoin, power consumption and hardware requirements are also increasing. So far, these problems have not been completely solved

the issue of central bank's digital currency: in addition to some problems of bitcoin itself, bitcoin will also face the challenges of central bank's digital currency in the future. Part of the value of bitcoin lies in the application of its blockchain, and the transaction mode of blockchain is also a major direction for the development of banks in the future. Applying the same technology, the central bank can better examine economic activities and carry out macro-control, which may be more concive to economic development. At the same time, we are not sure whether the digital currency issued with national credit will be easier to implement and get better development. However, when central banks make similar attempts, they are bound to compete with bitcoin to a certain extent

the foundation and early development of bitcoin are based on people's desire to build a fairer monetary system. But with the financialization of bitcoin and the admission of institutional investors, we suddenly found that a large number of bitcoin has been in the hands of financial giants. Bitcoin as cryptocurrency, its transactions have been outside the supervision, there is no legal requirement for institutional investors to disclose the large amount of transactions of bitcoin to ensure the fairness of the market, which also provides a lot of space for institutional investors to manipulate the market. Retail investors enter the market with a good vision of digital currency, but in the end, they become the target of big predators. After harvest after harvest, more capital is in the hands of financial giants

2. This depends on your research object
for example, if the slider slides on the desktop, it is external force
if the slider and the table as a whole are the research objects, it is internal force

3. A kind of granular material called silica gel can be put into a closed container together with the watch that has accumulated water. After a few hours, take out the watch and the water will disappear completely. This method is simple and economical, without any damage to the accuracy and life of the meter. The silica gel that has absorbed water for many times can be dried for several hours at 120 ℃ (the temperature of inction cooker is fixed at 120 ℃, and it can be stir fried). The water absorption capacity is renewable and can be used repeatedly
if the water is not serious, but there is a layer of fog in the glass, then wrap the watch tightly with several layers of toilet paper or absorbent flannel, and bake it at 15cm away from the 40W light bulb for about 30 minutes to eliminate the water vapor
do not bake the cover close to the fire, so as not to deform the cover when heated. It can also be worn on the wrist with the watch cover facing inside and the bottom shell facing out, and the moisture can be eliminated after two hours. If the water is serious, it's better to send it to the meter shop to wipe oil immediately to remove the moisture of the movement, so as to avoid parts rusting.

4. The force between the objects in the system is internal force. But if the objects in the system are subject to the friction of the objects outside the system, it is external force.
mechanical energy should consider the work done by various forces inside and outside the system, including force and reaction force. For example, if there is friction between two objects, the system mechanical energy of the two objects will be reced and converted into internal energy

5. When solving some problems, friction and elastic force are to see whether they belong to internal force or not, and to solve the physical problems of force analysis, the whole object should be regarded as a system. At this time, the internal force of a single object should not be included in the force of force analysis, but all the forces of the object should be included when studying the movement of a single object, In this way, we can solve a problem without making mistakes,.

6. If the sum of the external force vector is 0 (the system is not subject to external force is also one of the cases), then the concept of momentum conservation should be clarified first. What you think of as the interaction force between multiple objects (generally more than two) in the system is called internal force, and the friction force between objects in the system is also internal force, The friction between objects inside and outside the system is considered as external force

before asking a question, make clear the definition and concept of each key word in the question, and then compare it with 100 questions. The questions are nothing more than the set of various changes of basic concepts and mathematical operations

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7. Draw a picture, see the direction of the force, find the balance force

8. Unknown_Error

9. external force