Which is greater, static friction or sliding friction

The so-called coefficient of friction. Especially drawing.

Static friction is greater than sliding friction.

So if you're a senior in high school, you'll sometimes get exams or multiple-choice questions.

Another thing to note is that under the same conditions, the same object is used to calculate sliding friction.

Static friction and sliding friction are studied.

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.

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 the external force exerted on the object is equal to the sliding friction force, assuming that the maximum static friction force is equal to the sliding friction force, then the two forces are balanced, and the resultant force on the object is 0, and the object should remain in its original state and remain stationary, so only by providing a force slightly greater than the sliding friction force can the object produce acceleration consistent with the direction of the resultant force and make the object move, so the static friction force is slightly greater than the sliding friction force. Coincidentally, there are only two factors that affect its magnitude, namely positive pressure and friction factor, so the friction factor should be considered for the same object. The static friction factor is greater than the dynamic friction factor.

Because the contact surface between the object and the supporting filial piety stove is convex and uneven, when the object is in a static state, due to the action of gravity, the two contact surfaces will be slightly deformed, so that the two are well matched, and when the object moves, there is only macroscopic contact between the two contact surfaces, and it has not had time to have microscopic deformation and anastomosis to move to the next position.

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Analysis: 1When zoomed in, the contact surfaces between objects are uneven.

If the object is stationary on the tabletop, then the rough part under the wooden block will be partially embedded in the rough part above the desktop, just like the gear engagement, so that in order to make the wooden block move, there must be a part of the force to overcome the gravity force along the inclined downward component, so the force is greater than the frictional force when the object slides, that is, the static friction is slightly greater than the sliding friction;

2.When the external force exerted on the object is equal to the sliding friction, and we assume that the maximum static friction is equal to the sliding friction, then the two forces are balanced, and the resultant force on the object is 0, and the object should remain in its original state and remain stationary, so only by providing a force slightly greater than the sliding friction force can the object produce acceleration consistent with the direction of the resultant force, so that the object moves in motion, so the static friction is slightly greater than the sliding friction.

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.

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).

Static friction: There is a tendency for objects in contact with each other to move relative to each other, but the frictional force in relative motion has not yet been generated.

Kinetic friction: The friction force when relative motion has occurred between mold-slipping objects in contact with each other.

The main deficiency of the two is that one has not produced relative motion, and the other has produced relative motion.