Regarding sliding friction, what is the difference between sliding friction and rolling friction

In the seventies and eighties, many high school teachers spoke of the first type you mentioned. It is now thought that the second cause of friction is the resulting force. Smooth and frictionless is ideal.

The smoother the plane, such as two pieces of glass, the molecules on the two glass surfaces are too far apart, and the molecular gravity cannot adsorb, so the friction is less. But you may also think that it is not easy to break apart when two pieces of glass are attached together, but that is another matter, it is not a problem of friction, it is a problem of gas pressure.

For students in high school and below, it is more reasonable to follow the former analysis. The ideal state of smoothness and frictionlessness should be understood in this way. The smoothness here is the light that looks to the eyes, or touches the hands.

There is no light yet at the molecular level. Molecular bonding is said to have reached the level of molecules, the smoother it is, the closer the two sides are to the level of producing Coulomb force, then the molecules should be attracted, and the more light the attraction, the greater the friction.

Regarding sliding friction, it is more complicated, you can go to the physics competition book, where there are factors that affect friction.

Physics in high school doesn't consider so many factors, it just allows you to solve problems in a specific environment, and the public thinks that the smoother the plane, the less friction This is one-sided, and you said it above, I won't repeat it, so it's just so prescribed in physics. You can think that this rule is just right when you do the question.

Hehe......You've got a pretty good brain, not bad! But don't misdirect your efforts.

The theory of molecular bonding is a short-range nuclear force, which belongs to microscopic physics and is not applicable in macroscopic physics.

There are two kinds of friction, one is dynamic friction, and the other is static friction, sliding friction is not kinetic friction!

Sliding friction: When there is relative sliding between objects that are in contact with each other (and squeezing each other), the friction that arises between objects is known as sliding friction. Note that sliding Kiyono rubbing to answer hail shouts is not moving friction!

Rolling friction is actually static friction, taking tires as an example, tires and the ground are not sliding, are static contact, static contact in the way of rolling, because static friction is greater than dynamic friction, so the car in the acceleration race to start is to try to control skidding, a slip is sliding friction, wanton friction is small, so try not to slip but to the limit of fast skidding, so that you can get the maximum friction, the friction obtained without skidding is actually static friction, that is, rolling friction.

When an object slides on the surface of another object, the phenomenon that hinders the relative sliding between the two objects on the contact surface is called "sliding friction". The friction when there is a tendency to slide between objects but they have not yet slid is called static friction. Friction can be divided into dynamic friction and static friction, and dynamic friction can be divided into sliding friction and rolling friction.

When an object slides on the surface of another object, the phenomenon that prevents the relative sliding between two objects on the contact surface of the two objects is called "sliding friction". The friction when there is a tendency to slide between objects but they have not yet slid is called static friction. The causes of sliding friction are complex and inconclusive.

Modern friction theory believes that there are two main causes of sliding friction, one is the concave and convex meshing theory of friction, which believes that friction is caused by the rough and uneven surface of the object. When two objects are in contact, the uneven parts on the contact surface mesh with each other, causing friction to hinder the movement of the object; The second is the theory of molecular adhesion, which believes that when the distance between the molecules of two objects is small enough to the range of molecular gravity, the molecular gravity on the contact surface of the two objects will cause adsorption. The nature of friction needs to be further studied.

1. Friction heat. Because friction generates heat, it consumes mechanical energy; Sometimes, we also have to use a radiator to cool down, otherwise it is easy to damage the equipment.

2. Friction loss. Sliding friction can wear down the surface of an item, subjecting it to varying degrees of damage, resulting in property damage and even a threat to safety.

Conditions for the generation of sliding friction:

The contact surface is rough.

Two objects are touching each other and are squeezed against each other.

There is relative motion between objects.

Magnitude and direction of sliding friction:

Magnitude: The magnitude of the sliding friction f is proportional to the positive pressure, and the shed comb chain is f = n. is the dynamic friction factor: it is related to the material and roughness of the contact surface. The roughness of the contact surface is related to the elastic force between the contact surfaces.

The magnitude of the sliding friction is slightly smaller than the maximum static friction fmax. In the usual calculations, the maximum static friction can be considered to be equal to the sliding friction.

Factors affecting the magnitude of sliding friction:

1) The amount of pressure on the object. The greater the pressure on the contact surface, the greater the sliding friction.

2) The roughness of the surface that is in contact with the object (the roughness of the contact surface). The rougher the contact surface, the greater the sliding friction when the pressure on the object is the same.

3) The magnitude of sliding friction is independent of the contact surface area.

4) The friction force of the slide chain has nothing to do with the speed of the object.

I'm old, nagging a little, you just look at the summary and examples, my own understanding, there should be no problem. If you have any questions, you are welcome to ask

The difference between static friction and the other two is that there is a relative displacement between the other two friction objects (the contact surface has moved relatively), while the two objects of static friction have no relative displacement (both contact surfaces do not move), they are relatively stationary, so it is called static friction.

The difference between sliding friction and rolling friction, sliding friction, between two objects, the contact surface of one object does not move (the contact surface does not change, it is always that one face), and the contact surface of the other object moves; Rolling friction is that the contact surfaces of two objects change, both move relatively, and the relative velocity of the two is the same, if the speed is not the same, it is sliding friction plus rolling friction. (Because the relative velocity is different, there must be one surface moving slowly relative to the other, then there must be some moments when one face moves and the other surface does not have time to move, that is sliding friction).

Short summary:

Static friction: The two surfaces of two objects touching are not moving, there is no relative velocity and relative displacement.

Sliding friction: The two faces of two objects in contact have a motion, relative velocity and relative displacement.

Rolling friction: The two surfaces of two objects in contact are understood, and the speed of movement must be the same is pure rolling friction, and there is not necessarily a relative displacement.

To nag a little more, explain that the last one does not necessarily have a relative displacement: when rolling friction occurs, one of the two objects must be a cylinder (cone) or a ball, something that can roll, and if the other object is the same as the previous object, and both are rolling at the same speed, then there is no relative displacement; If the other object is not rollable, then there is a relative displacement.

I'm afraid you don't understand, I'll give you an example:

Static friction: A static wooden block on a rough table that is subjected to horizontal thrust is static friction.

Sliding friction: A sliding wooden block on a rough table that is subjected to horizontal thrust is a sliding rub.

Rolling friction: The barrel is rolled on the tabletop, or two rollers are rolled opposite each other.

The link below is also mine and you can check it out.

What is the difference between rolling friction and sliding friction? The difference between rolling friction and sliding friction is that the two friction surfaces of sliding friction are fixed, while one friction surface in rolling friction is changing, and the contact point is constantly changing.

Rolling friction refers to the friction that occurs when an object rolls on top of another object. Sliding friction refers to the frictional force that occurs when an object slides along the surface of another object. Extensions:

1. The rolling friction is much smaller than the maximum static friction and sliding friction, and in general, the rolling friction is only 1 u002f40 to 1 u002f60 of the sliding friction resistance. Therefore, rolling an object on the ground will require a lot less effort than pushing the object and sliding. 2. Sliding friction refers to the frictional force generated when an object slides along the surface of another object.

The sliding friction experienced by the object is in the opposite direction to the direction of its movement, so friction occurs. Whoop Debate @2019