Is there frictionlessness? Is there a difference between friction and friction?

Strictly speaking, there is none, as long as there is as long as there is relative motion between molecules. The molecules then collide, causing the relative sliding of the objects to be resisted.

And even without friction, a perpetual motion machine cannot be made. The definition of a perpetual motion machine is to do work to the outside world, and frictionlessness does not mean that it can always do work to the outside world.

There is a frictionless situation, and frictionless cannot be made into a perpetual motion machine, which does not violate the conservation of energy.

It needs to be explained again that the perpetual motion machine is not called forever moving, but must continue to do external work without energy. Otherwise, the earth is always rotating or perpetually moving, so what's the use?

Frictionless allows the machine to move continuously, which does not violate the principle of conservation of energy! Because in this case the machine does not absorb energy and does not give energy, energy is still conserved! However, once he gives energy outward, that is, to drive other machines to operate, then energy is not conserved - energy is created!

So what this brother said is missing (am I right about gender?) ）

Frictionless means that the coefficient of friction is zero, which requires absolute smoothness, which is impossible! From the micro**, the molecules (or atoms, etc.) on the surface of the object have a strong effect on the molecules on the surface of the object that touches him, causing the relative sliding between the objects to be resisted, you say, will this force disappear?

There is no friction if there is no movement or no movement trend.

There is no movement without friction, there is no friction in a vacuum.

But there is no absolute vacuum, we live in a world surrounded by gases, even in space, there are thin gases. Friction occurs due to the relative velocity of motion between the gas and the moving object.

There is no such thing as a perpetual motion machine, unless all the gas can be pumped clean, which will create a pressure difference and annihilate the vacuum.

There is friction within the human sphere.

A perpetual motion machine violates the conservation of energy.

Even if there is no friction, there will be no perpetual motion machine.

Because it's impossible to continuously convert one form of energy into another.

Strictly speaking, to make an object free from frictional force must be satisfied: it is not subject to 'force' or the support surface is smooth. However, all objects on the earth are subject to the attraction of the earth, and at the same time, they are not smooth (with friction) under normal conditions, and there is generally no frictionless situation, and the general formula is f=nu

However, there are also some movements that can be seen as frictionless movements, such as hovercraft, hovercraft, etc.

This is not the meaning of the perpetual motion machine, the perpetual motion machine can always do unlimited external work. As long as you don't do external work, you can always move, and no friction is an ideal situation of not doing external work.

I think there will be, but a perpetual motion machine is impossible because energy has to be conserved and cannot be increased.

If there is no friction, there should be no air, and the surface of the object should be absolutely smooth, so that there can be no friction.

There is no frictionless situation.

Looking at the universe, under the action of gravity, the stars are moving according to a certain trajectory ......

Aren't these friction-free situations?!

In a vacuum there is no air, there is no substance, so there is no friction.

I don't think it's in daily life.

A. The bottle is stationary on the horizontal plane, and the bottle has no movement and movement tendency relative to the horizontal plane, so there is no friction, so A is wrong

B, the bottle is stationary on the inclined tabletop, due to the gravity of the bottle, the bottle has a downward movement trend along the inclined surface, so the bottle is subjected to the static friction along the inclined surface, so B is correct

c, Gippei touches the bottle is held in the hand, the bottle mouth is facing up, according to the state of the bottle to get the bottle to be 0, in the vertical direction of the bottle by gravity, must also be affected by the hand to its static friction so C correct to talk.

d. The bottle is stationary on the floor of the train moving at a uniform speed, and there is no relative movement trend, so there is no friction, so D is wrong

Therefore, I chose: BC

According to your description, I personally think that, first of all, there is a difference between "friction" and "friction". The first point, in essence, "friction" can refer to the effect caused by the force of multiple aspects, and "friction" only refers to the effect of the force caused by the wear force. The second point is Li Ying, from a macro point of view, "friction" is to include the effect of "friction", of course, the specific situation please according to the actual situation, I hope the above suggestions can bring you some help, thank you.

What would the Earth be like if there was no friction -- If there was no friction, we wouldn't be able to walk. Because he could neither stand nor walk. For example, when walking on the ice, because of the ice slippery, I was tired and sweating after walking a short distance.

If there was no friction, the road would be smoother than ice, and people would only feel better if they fell to the ground. If there is no friction, the screws cannot be tightened, and the nails nailed to the wall will automatically loosen and fall. The tables and chairs at home will be spread out, and they will slide over the floor with missing wheels, and they will slide over, and they will not be usable at all.

When pushing the table, when there is no thrust, if there is no friction, then the object has to move to the right, so the object has a tendency to move to the right, so the object will be subjected to a leftward static friction force that hinders this tendency of it.

For another example, in the process of transporting the goods upwards with the conveyor belt, if there is no friction, the goods should slide down the inclined plane, so the object has the tendency to slide along the inclined plane, so the conveyor belt has the effect of static friction along the upward slope of the goods, so as to hinder the movement trend of the goods sliding downward.

If there is no friction and medium resistance, the total amount of mechanical energy remains untouched when the object only undergoes the mutual conversion of kinetic energy and potential energy.

That's the effect of no friction.

Pay attention to hills, peaks, and valleys. These are called bumps or material deformation. They appear on rough surfaces, and even flat surfaces may have slight irregularities.

Now imagine trying to rub them against each other. Take a moment to feel in your mind the opposition you might encounter as they run into each other.

Friction is the most common type of friction** and includes static friction (when your object is stationary and you try to make it move) and dynamic friction (when your object is already moving and you need to keep it moving).

This is why the friction that the wheels experience while rolling, known as rolling friction, is much lower than other types of friction, as well as the deep grooves that the tires have. This is also the reason why the flatter and more uniform the surface, the less friction there is.

Plane friction. But for a completely flat surface, the friction remains, and the roughness of the above form is no longer present.

Perfectly flat surfaces nucleate each other – in other words, they try to stick to each other. This is called adhesion and can be caused by a variety of causes:

van der Waals force, a class of force that causes them to attract each other due to the force of attraction between electric dipoles on the surface of a material. In this case, the material is considered to be disperse-adherent.

Chemical bonding, where the atoms of two materials exchange electrons in some way and are chemically attached to each other. For example, hydrogen in one material may form a fragile bond with a strongly electronegative element in another.

These forces are usually weak enough that they can be easily broken once you lift an object – but not so weak that overcoming the attraction by dragging an object doesn't cause a problem.

Finally, a definition.

Friction, then, is not so much a force as the sum of very small forces and irregularities along the edges of the surface.

It's possible to model it as a real force – in fact, most high school textbooks do just that – but it's important to recognize that it's just a convenient abstraction. In other words: friction is forcing Santa Claus to decorate the window on top of a very complex reality for a happy man in a fat suit.

Static friction and sliding friction are two different types of friction between the surfaces of an object. Static friction is the resistance of the relative motion of the object when the surface of the object is in contact, while sliding friction is the resistance between the surfaces of the object when the object is in relative motion. Here are the differences between the two types of friction:

Static friction and sliding friction have different states of motion.

Static friction occurs when the surface of an object comes into contact and the object does not move when the resistance of two objects in relative motion is greater than the force exerted by an external force. In this case, the object stops in place and is at rest.

Sliding friction occurs when the surface of an object slides relative to each other, and the drag between the two objects increases as the speed of motion increases, which causes the object to accelerate and slow down until it stops or reaches a stable velocity.

The forces of static friction and sliding friction are different.

The resistance of static friction is usually greater than that of sliding friction and this is because the force of static friction prevents the object from starting to move and more force needs to be applied to overcome it.

Sliding friction usually has less resistance than static friction because once the object starts sliding, the contact area between the surfaces decreases and the friction decreases.

The coefficients of static friction and sliding friction are different.

The coefficients between static friction and sliding friction are different, and even if they are two objects of the same size, the coefficient of static friction and the coefficient of sliding friction between them may be different.

Generally, the coefficient of static friction is greater than the coefficient of sliding friction because when the surface of the object comes into contact, the small irregularities between the surfaces create more friction, whereas once the object starts moving, the contact area between the surfaces decreases and the friction decreases with it.

The key to distinguishing between static and sliding friction lies in the observation of the state of motion and the magnitude of the force, as well as the understanding of the coefficients

When an object and another object move along the tangential direction of the contact surface or have a tendency to move relatively, there is a force between the contact surfaces of the two objects that hinders their relative motion, and this force is called friction. This phenomenon or property between the contact surfaces is called "friction".

Friction can be both beneficial and harmful, but in most cases it is detrimental, for example, friction during machine operation, resulting in unbeneficial loss of energy and shortening of machine life, and reducing mechanical efficiency.

Therefore, various methods are often used to reduce friction, such as adding lubricating oil to the machine. But friction is indispensable, for example, people walking, car driving must rely on the ground and feet and wheels friction. On muddy roads, it is difficult to walk because the friction is too small, and it is easy to slip, and the wheels of the car will also spin, that is, the wheels will rotate without the carriage moving forward.

Therefore, in some cases, it is necessary to try to increase friction, such as sprinkling some ash or sand on a road that is too slippery, and adding snow chains to the wheels.

Triboelectric activation. <>

1. The causes are different.

If two objects that are in contact with each other and squeezed each other, and are relatively stationary, if they only have a relative sliding tendency under the action of external forces, but do not slide relatively, the force that prevents them from sliding relative is called "static friction". When static friction occurs two objects are at rest relative to each other.

Sliding friction is the force generated between two objects with relative sliding on the contact surface that prevents them from sliding relative to each other. Sliding friction requires relative motion.

2. The direction of the force is different.

The static friction force is always opposite to the direction of the relative movement trend, and is not necessarily tangent to the contact surface, which can be judged by the equilibrium method. It can be a drag force or a driving force, and a moving object can also be subjected to static friction.

The sliding friction is always tangent to the contact surface and opposite to the relative direction of motion of the object.

3. The magnitude of the force is different.

The maximum static friction is greater than the sliding friction and the rolling friction is much smaller than the maximum static and sliding friction.

<>1, the static friction force is variable, which is related to the state of the force, and is generally solved by using the force system equilibrium.

Sliding friction is equal to the coefficient of friction multiplied by the supporting force of the contact surface, and the former is related to the roughness of the contact surface, i.e. the sliding friction can be calculated by formula.

2. The object is placed on a horizontal plane, give it a pulling force, as the pulling force increases, as long as the object does not move, the static friction force is equal to the pulling force, as it increases, when it increases to a certain extent, the object moves, and the maximum static friction force is reached at this time, the magnitude of this force is about the same as the magnitude of the dynamic friction force, and it is generally assumed that the maximum static friction force is equal to the kinetic friction force. After that, the kinetic friction force does not change, which is equal to the coefficient of friction multiplied by the supporting force of the contact surface. At this point, the force is unbalanced, and the object moves at an accelerated pace.