Is friction elastic
Publish: 2021-04-16 19:47:10
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
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
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)
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.
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.
If the surface roughness is constant, the relationship between the friction force and the pressure is in direct proportion, f = NK, where k is the roughness coefficient and N is the pressure. At this time, the friction force is related to the elastic force (the condition of friction force must have elastic force)
The direction of the elastic force is opposite to that of the external force. Because there are many kinds of deformations of objects, the elastic force proced also has various forms The direction of friction is opposite to the direction of relative motion (or relative motion trend). Friction is divided into static friction, rolling friction and sliding friction 
extended data:
the elastic force can only exist in the place where objects contact each other, but it does not necessarily have the effect of elastic force between objects that contact each other. Because the generation of elastic force not only needs contact, but also interaction
the elastic force is proced between the objects which are in direct contact and have elastic deformation. Generally speaking, pressure, supporting force and pulling force are elasticity. The direction of elasticity is always opposite to the direction of deformation. The direction of pressure or supporting force is always perpendicular to the supporting surface and points to the pressed or supported object
the biggest difference in friction is the difference between static friction and other friction. Some people think that static friction should not actually be counted as friction. Other frictional forces are related to dissipation: it reces the relative velocity of objects that rub against each other and converts mechanical energy into heat energy
6. 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.
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.
7. No, elastic force is the force proced by deformation, and friction force is the force proced by motion
8. 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
(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
9. No, the real reason for the elastic force is the force proced when the object returns to its original shape after elastic deformation
but the friction force is because there are always small unsmooth protrusions or depressions on the surface of the object, These protrusions and depressions will proce the phenomenon of "meshing" (protrusions of one contact surface fall into depressions of another contact surface), so the force to prevent the movement of objects is fundamentally different
the elastic force is only the cause of friction, and the friction force does not actually belong to elastic force
but the friction force is because there are always small unsmooth protrusions or depressions on the surface of the object, These protrusions and depressions will proce the phenomenon of "meshing" (protrusions of one contact surface fall into depressions of another contact surface), so the force to prevent the movement of objects is fundamentally different
the elastic force is only the cause of friction, and the friction force does not actually belong to elastic force
10. Difference: friction is the force that hinders the movement of an object, while elasticity is the force that the deformed object wants to return to its original state
connection: from formula F= μ F shows that if there is friction, there must be elastic force (i.e. pressure). But the existence of elasticity does not necessarily have friction, because if there is only positive pressure and no movement trend, there will be no friction.
connection: from formula F= μ F shows that if there is friction, there must be elastic force (i.e. pressure). But the existence of elasticity does not necessarily have friction, because if there is only positive pressure and no movement trend, there will be no friction.
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