Is elasticity friction

1. Two different forces
friction is the force proced when two objects are in non smooth contact and have relative motion
elastic force does not necessarily have friction force; friction force must have elastic force

since elastic force is nature force, tension, pressure, etc. belong to elastic force

2. In essence, friction is caused by the mutual contact between two objects, the subtle concave and convex occlusion and the mutual attraction of atoms close to each other.
it is far fetched to use elastic force to explain the generation of friction.
a small experiment is helpful to understand this problem.
cut a piece of metal lead with a sharp knife, and then press them together, The greater the pressure, the stronger the adhesion.
this experiment is explained by elasticity

3. No. force is divided by nature. Elastic force, gravity and friction force.
elastic force is the force of a deformed body on a deformed body, and the generation of friction force is based on elastic force.
simple calculation formula F= μ F( μ Is the coefficient of friction)

4. The elastic force is caused by the mutual positive area pressure between objects, which should be in the opposite direction and perpendicular to the contact surface of two objects
the friction force is not necessarily in the same direction or in the opposite direction, but it must not be perpendicular to the stress surface of two objects.

5. No
one of the most critical elements of elasticity is the deformation of an object. Like springs

friction is just a force proced by two objects moving or tending to move relatively, without deformation.

6. 1. Friction
(1) definition: two objects in contact with each other, when they are about to move or have moved relative to each other. It creates a force on the contact surface that prevents relative motion. This force is called friction
(2) friction between objects must have the following three conditions:
first, objects contact and squeeze each other
Second, objects have relative motion trend or relative motion
Third, the indirect contact surface of objects is rough

2 Sliding friction
(1) definition: the friction generated when an object slides on the surface of another object is called sliding friction
(2) the experiment to study the relationship between the sliding friction and which factors: why do we use the spring scale to pull the wood block to do uniform linear motion? This is because the spring scale measures the tension rather than the friction. When the block moves in a straight line at a constant speed, the pulling force in the horizontal direction of the block and the friction between the board and the block are a pair of balance forces. According to the balance condition of the two forces, the tension should be equal to the friction. So we measure the tension, that is, we measure the friction. A large number of experiments show that the sliding friction is only related to the pressure and the roughness of the contact surface. The greater the pressure, the greater the sliding friction; The rougher the contact surface is, the greater the sliding friction is
(3) sliding friction is the force that hinders the relative movement of objects in contact with each other, not necessarily the force that hinders the movement of objects. That is to say, friction is not necessarily resistance, it may also be the motive force to make the object move. It should be clear that the object in contact with each other is the reference object to block the "relative motion"“ "Object motion" may refer to other objects. For example: in the experiment, when a weight is placed on the block and the block is pulled by a spring scale to move in a straight line at a constant speed, the weight changes from static to moving with the block e to the static friction of the block. The specific situation is: when the wood block is pulled forward from rest, the weight will slide backward relative to the wood block, and the wood block will give the weight a friction to prevent it from sliding backward, and the direction of the friction is forward. Therefore, the weight does not slide relative to the wood block, and the friction force is the static friction force
(4) the sliding friction has nothing to do with the speed of the object movement, and has nothing to do with the size of the contact area between objects
(5) in the study of practical problems, in order to simplify, the "idealized" method is often used. For example, if one object is placed on the smooth surface of another object, the "smooth" means that there is no friction between two objects if they move relative to each other< Static friction: when an object and another object move along the tangent direction of the contact surface or have a trend of relative motion, there is a force between the contact surfaces of two objects that hinders their relative motion. This force is called friction. If two objects, which are in contact with each other and relatively still, only have the tendency of relative sliding under the action of external force, but no relative sliding occurs, the force between their contact surfaces hindering relative sliding is called "static friction"
2. The conditions of static friction:
1. The contact surface is rough
2. Two objects contact each other and squeeze each other< (3) there is a tendency of relative motion between objects< 2. Direction of static friction:
1. Direction: tangent to the contact surface and opposite to the relative motion trend of the object. The so-called relativity is based on the reference frame of the object exerting the friction force< (2) determination of the direction of the relative motion trend: assuming that the contact surface is smooth and there is no friction, the direction of the relative motion trend can be determined by looking at the relative motion direction of the object.
3. The size of the static friction:
see Fig. 2 device. Graally increasing the mass of the sand in the bucket, the tension t on M increases graally. Because m is in a static state, the static friction f is always balanced with the tension t, Therefore, the magnitude of static friction graally increases. When the mass of the sand increases to a certain extent, it is found that the block suddenly moves relative to the horizontal plane, so the static friction between the block and the table no longer exists. According to the above analysis:
① maximum static friction: there is a maximum static friction, which is called maximum static friction. It is equal to the minimum external force required to make the object just move
② the static friction is not a fixed value, but changes with the actual situation, and the value is between zero and the maximum static friction FM. Its value can be determined by the motion state of the object
static friction is very common. For example, the bottle and brush in hand will not slide, which is the result of static friction. The ability to weave thread into cloth and sew cloth into clothes also depends on the static friction between yarns. There are many applications of static friction in proction technology. For example, a belt conveyor relies on the static friction between the goods and the conveyor belt to transport the goods elsewhere< When one object rolls on the surface of another object without sliding or has the tendency of rolling, the rolling friction is caused by the deformation of the contact part of the two objects, which is called rolling friction
5. Calculation of friction
formula F can be used to calculate friction= μ N calculation, where μ It is the friction coefficient, n is the pressure on the surface
6, about the essence of friction
1. Concave convex meshing theory is a theory about the essence of friction put forward by scientists from the 15th century to the 18th century. Meshing theory holds that friction is caused by the rough and uneven surface of objects in contact with each other, Many concave and convex parts of the contact surface mesh with each other. If an object slides along the contact surface, the convex parts of the two contact surfaces collide, resulting in fracture and friction loss, which forms an obstacle to the movement.
2. Adhesion theory. This is a theory about the essence of friction after concave and convex meshing theory. It was first put forward by British scholar dessajolius in 1734, He thinks that the friction between two metals with polished surfaces will increase, which can be explained by the increase of their molecular gravity when the surfaces of two objects are fully contacted.
since the last century, with the development of instry and technology, the study of friction theory has been further deepened, and by the middle of last century, a new theory of friction and adhesion was born, No matter how smooth or rough the two surfaces are, there are many tiny bumps on the atomic scale. If the two surfaces are put together, the top of the micro bumps contacts, and there is a gap of 10-8 m or more between the contact surfaces outside the micro bumps, If the pressure is very small, the top of the micro bump will deform elastically; If the normal pressure is larger than a certain value (about a few thousandths of a Newton on each bulge) and exceeds the elastic limit of the material, the top of the micro bulge will undergo plastic deformation and be pressed into a flat top. At this time, the distance between the two objects in contact with each other will be reced to the range of the molecular (atomic) force, Atomic adhesion is proced on the two tightly pressed contact surfaces. In order to make the two relatively contacting surfaces slide, a tangential force must be applied to one of the surfaces to overcome the gravitational force between molecules (atoms) and cut off the contact points generated in the actual contact area, which leads to friction.
through continuous experiments and analysis and calculation, the friction between the two surfaces is generated, It is found that the mechanisms proposed by the above two theories can proce friction, and the mechanism proposed by the adhesion theory is more common than that proposed by the meshing theory. However, in different materials, the performance of the two mechanisms is biased: for metal materials, the friction proced is mainly adhesion, while for wood, the friction proced is mainly meshing, At present, there is no final conclusion, which is still under further discussion.
5. The size of friction force is determined by two factors:
1. The roughness of contact surface.
2. The pressure on the surface

7. 1、 If you want to take the high-speed railway, you have to go to Xi'an north station. The high-speed railway is fast. You can get to Huashan North Station in half an hour. There are many flights. There are 12 in the whole day. The first one is 7:00, the last one is 19:30, and the second-class fare is 59 yuan; Except for the high-speed railway, other trains take at Xi'an railway station. It takes one and a half hours to Huashan station (not Huashan North Station). The hard seat ticket price is 20 yuan. There are 24-hour flights all day. When the railway station comes out, it is necessary to take a taxi to Huashan
Second, take a long-distance bus. There is a special bus to Huashan at the East passenger station of Xi'an. There are many times. There is a bus from half an hour to an hour, and the departure time is quite punctual. The ticket price is about 43 yuan. You can get down to Huashan (Yuquan Road), which is the foot of Huashan Mountain. The journey is less than 2 hours; You No.1 is also available in the parking lot of the East Square of the railway station to Huashan. There are few buses, leaving at 7 a.m.
it's best to spend two days to play Huashan. On the first day, you can go up the mountain in the daytime, watch the sunset at Xifeng in the evening, and then stay overnight. On the second day, you can go to Dongfeng to watch the sunrise, There are many local private hotels on both sides of Yuquan Road in front of Huashan Mountain, which cost 60 yuan a night for poor conditions and 100 yuan a night for better conditions; It's expensive to stay in a state-owned hotel on the mountain. It's not very cost-effective. You can live in Taoist temples, such as the alchemy furnace and Zhenyue palace. The standard room costs 350 yuan a night, and more than 60 yuan a person

8.

the first way of living in the UK: dormitories on campus

British universities generally provide dormitories for students. It can be divided into several categories: halls of residence, flats and
houses, etc. the former is usually a traditional room, including reception room, social hall, sports facilities and laundry room, etc. Now most of them are apartment system, with many bedrooms, one person in each room, and public kitchen, toilet and other facilities. The rent of dormitories provided by schools is generally cheaper, and water, electricity, gas and so on are included, and some of them are regularly cleaned by special personnel. There are two kinds of dormitories, the former includes breakfast and dinner, but there is no dinner on Sunday. Self cooking dormitory usually provides cook, refrigerator, microwave oven and other facilities, you can cook according to your own taste

the advantage of applying for school dormitories is that the safety is guaranteed to the greatest extent, because the management of school dormitories is very strict, and the school dormitories generally provide water, electricity and Internet services for students, and the complete services give a reassurance to students who have just studied abroad. The cost of this scheme will be slightly higher than the other two accommodation schemes, and e to the unified management of the school, the flexibility of foreign students' independent choice is less. Most schools in the UK can provide in school accommodation for international students

the second way of living and lodging in the UK: the advantage of home boarding is that it can integrate into the life of local people as soon as possible. Most of the international students who choose to live in local families are middle school students, and these local families have no criminal records. International students live in the host family, and the local family provides accommodation and two meals in the morning and evening, and the school provides lunch. The biggest advantage of this program is that it can quickly integrate into the local life, but there are also differences between the cultural habits of foreign students and local families

the third way of living and accommodation for studying abroad in the UK: renting out of school

you can choose the most suitable house for yourself. You can choose the house according to your personal preferences and economic ability. You should do everything yourself, and exercise your independent living ability, but you should prevent traps

1. When renting a house outside school in the UK, a contract must be signed for more than half a year, or the lease term can be reced through negotiation with the landlord, but it should be at least three months. If only one month's rent is a breach of contract, the landlord has the right to confiscate the deposit

In order to avoid unnecessary trouble, it is necessary to agree on the rent in advance, understand the reputation and living habits of the tenants

If you rent a house through an intermediary, you need to know the terms of the intermediary fee in the contract and whether the landlord's information is true. Don't rent a house through the rental information posted in supermarkets, shops and roads. This kind of information source is convenient, but the reliability is not credible