Why is rolling friction dynamic friction and what is the difference between sliding friction and rol

The landlord first read the relevant instructions on the rolling friction on the following handout, and the general tribological principles of the book have relevant introductions, just look at it.

A cylinder or ball moves along the contact surface under the action of the moment, and when the relative velocity between two contact objects at the contact point is zero, it is called [pure rolling]. Theoretically, there should be no friction when the relative velocity is zero. But in engineering practice, there is no real pure rolling.

Therefore, the resistance generated in rolling is called rolling friction.

The landlord's question said that the relative stillness should be for [pure rolling], and the dynamic friction behind it should refer to the actual rolling friction.

Causes of rolling friction.

Microscopic sliding. Pure scrolling does not exist in actual engineering. There is a microscopic relative slip of the surface as it rolls. The relative resistance to motion when overcoming microscopic sliding is the rolling friction force.

Elastic hysteresis. When the steel ball rolls on an elastic surface (Fig., first tensioning the material in front and then intrapting the material that has been tensioned at the leading edge, this requires work; At the same time, the elastic material behind the rolling element enters a relaxed state. This elastic recovery can propel the ball forward.

This ability to rebound is less than the work done by the rolling element when it tensions and intraps the leading edge material. In the process of tensioning-relaxing, energy is inevitably consumed, which is the work consumed by friction. That is, the rolling friction resistance caused by elastic deformation.

This phenomenon is also known as elastic hysteresis.

Plastic deformation. If the contact pressure on the rolling surface is too high, a groove will form on the surface. The soft metal surface creates a large groove width.

The appearance of this groove is a kind of plastic deformation. As the rolling elements roll repeatedly in the groove, the groove surface is work-hardened, and the groove width does not continue to expand into an elastic state.

Adhesion effect. Adhesive contacts also occur on the interface during rolling contact. However, due to the minimal slip of the interface, the breakage of the adhesive joint is different from the shear in the sliding, but the contact is elongated, peeled off and disconnected in turn.

The force required to break the adhesive junction is much less than the force required to cut all the contacts on the entire interface. As a result, the amount of material that adheres to the rolling contact is so small that it can usually be omitted. Therefore, although the presence of the boundary film can reduce the adhesion, it is estimated that the boundary film has little effect on the rolling friction resistance because the adhesion itself is not important.

Rolling friction is a kind of dynamic friction, rolling friction can be understood as friction in the process of friction, the position of the body changes in the process of friction, the rolling of the wheel of the stock, and the rolling or sideways movement of other objects. Therefore, there is no objection to classifying it as kinetic friction.

It's easy to understand when you look at him as a whole.

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.

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

What is the difference between rolling friction and sliding friction? The difference between rolling friction and sliding friction is as follows: 1. The working mode is different

Sliding friction is a fixed two friction surfaces, one of the friction surfaces 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 another object. Sliding friction refers to the friction generated by an object when it slides along the surface of another object.

2. The friction is different: 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 nanofriction resistance. Therefore, rolling an object on the ground will require a lot less effort than pushing the object and sliding.

Sliding Minbi friction refers to the frictional force that occurs when an object slides along the surface of another object. The direction of the sliding friction experienced by the object is opposite to the direction of its motion, and therefore, friction occurs. @2019

Sliding friction: It is the friction when two objects slide relative to each other. (e.g., rubbing the blackboard with a board eraser, the friction between the board eraser and the blackboard).

Rolling friction: It is the friction that occurs when rolling. (e.g. cycling friction between the wheels and the ground).

Static friction: It is when two objects do not move relative to each other, but there is an external force that is about to move relative to each other. (e.g. the friction between the hook and the wall on which the clothes are hung).