With regard to friction, what is friction

This question should be considered in two processes:

1.Because when only F1 is added, the object moves in a uniform straight line to the east, so the sliding friction is 10N to the west, remove F1, and add F2 until the object velocity is 0, the object velocity direction remains unchanged, so the sliding friction of the object is still 10N to the west.

2.But from this point on, the object begins to do a uniform motion until the velocity is 0, after which the object is stationary, because the maximum static friction is greater than the sliding friction, that is, the maximum static friction is greater than 10n, and f2=10n direction to the west, so the object finally stops, and the static friction force is 10n direction to the east.

Upstairs, let's figure out the definition and nature of friction!

The instantaneous friction does not change! Because the state of exercise has not changed!

It's still 10 Ox, and the direction is west!!

Otherwise, as the two said, the pulling force and the frictional force cancel out, and the acceleration is zero, and the object will not move forever? This is patently ridiculous!

Solemnly agree with Lou's opinion!!

I didn't say that the other comrades didn't learn physics well, and they answered as if they were the real thing.

I won't repeat the answer, just pay attention to the question carefully. Anyone who has ever encountered this kind of thing when they were studying physics.

The direction of friction is opposite to the direction of relative motion or relative motion trend.

Friction is also divided into static friction and sliding friction. In this problem, the object is in relative motion to the ground, so it is a sliding friction force. The magnitude of the sliding friction is 10n

The magnitude of the sliding friction depends on the contact surface and the positive pressure after removing F1 and replacing F2 with the initial motion direction of the object or to the east, the contact surface and the positive pressure are unchanged, so the direction of the friction force is still west, and the magnitude is still 10Nf Mo = 10n, direction to east.

The friction is magnitude 10n and the direction is east

The magnitude is 10n (equal to the pulling force) and the direction is horizontal to east (opposite to the direction of the pulling force).

The friction is magnitude 10n and the direction is west.

1. Friction.

1) Definition: Two objects in contact with each other when they are about to occur or have been in relative motion. A force that hinders the relative motion is created on the contact surface, and this force is called friction.

2) The following three conditions must be met for friction between objects to occur:

First, objects are in contact with each other and squeezed.

Second, the contact surface is not smooth.

Thirdly, there is a tendency or relative motion between objects.

2. Sliding friction.

1) Definition: The frictional force generated when an object slides on the surface of another object is called sliding friction.

2) Experiment to study what factors are related to the magnitude of sliding friction: why use a spring scale to pull a wooden block to do a uniform linear motion during the experiment? This is because the spring scale measures the amount of tension and not the amount of friction.

When the wooden block moves in a uniform linear motion, the tensile force in the horizontal direction of the wooden block and the frictional force of the wooden board on the wooden block are a pair of balancing forces. According to the condition of the balance of the two forces, the magnitude of the pulling force should be equal to the magnitude of the friction force. Therefore, the magnitude of the tensile force is measured, that is, the magnitude of the friction force is measured.

A large number of experiments have shown that the magnitude of sliding friction is only related to the amount of pressure and the roughness of the contact surface. The greater the pressure, the greater the sliding friction; The rougher the contact surface, the greater the sliding friction.

3) Sliding friction is the force that hinders the relative motion of objects in contact with each other, not necessarily the force that hinders the motion of objects. That is, friction is not necessarily a drag, it can also be the driving force that makes an object move, and it should be clear that the obstacle to "relative motion" is to use objects in contact with each other as references. "Object motion" may be based on other objects.

For example, in the experiment, when a weight is placed on the wooden block and the wooden block is pulled by a spring scale for uniform linear motion, the weight is changed from rest to motion with the wooden block due to the static friction force of the wooden block on it. The specifics are:

When the block moves forward from rest by tension, the weight slides backward relative to the block, and the block gives the weight a frictional force that prevents it from sliding backwards, and the direction of this friction force is forward. Therefore, the weight does not slide relative to the wooden block, and the friction at this time is the static friction.

4) The magnitude of sliding friction has nothing to do with the speed of the object's motion, and has nothing to do with the size of the contact area between the objects.

5) When studying practical problems, the practice of "idealization" is often used for the sake of simplification, such as one object on the smooth surface of another object, which means that there is no friction between two objects if they are in relative motion.

3. Static friction.

Static friction is produced by the interaction of two objects that are at rest with each other.

4. Rolling friction.

When an object rolls without sliding or has a tendency to roll on the surface of another object, the obstruction effect on rolling due to the deformation of the two objects under pressure in the contact part is called "rolling friction".

1) When two objects in contact with each other are in relative motion or have a tendency to move relatively, there is a force between the contact surfaces of the two objects that hinders their relative motion, which is called friction. Friction is essentially caused by electromagnetic forces.

2) The following four conditions must be met for friction between objects to occur:

First: two objects touching each other.

Second: two objects squeeze each other, deform and have elastic force.

Third: two objects are moving relative to each other or have a tendency to move relative to each other.

Fourth: the contact surface between two objects is rough.

All four conditions are indispensable.

Where there is elasticity, there is not necessarily friction.

However, where there is friction, there must be elasticity.

Friction is a contact force and a driven force.

The way to solve such problems is to start with the active force or the active prerequisites, and conduct a force analysis.

Common Method: Hypothetical Method – The method of assuming the existence of forces.

When you walk on the road, your feet don't slip on the ground because of the friction between the sole of your shoe and the ground (static friction). Conversely, when you're walking on snow, ice, or extremely slippery tiles, you'll slip because there's too little friction between the soles of your shoes and the "ground". This two-pronged experience tells us that friction is essential for us to walk.

There is friction not only in the case of relative motion between two objects, but also between two objects that are in contact with each other but do not have relative motion. The reason why you are able to stand on the slope without sliding down is because the soles of your shoes have enough friction with the slope. The reason why you are able to nail two planks together with a nail is because the nail has enough friction with the plank.

In fact, as long as two objects are in contact with each other, and they have a tendency to move relatively, there must be friction.

From this we can say that the force that hinders the relative motion between two objects in contact with each other (or the tendency to hinder their relative motion) is called frictional force.

Definitions and Interpretation.

Two interacting objects, when they are in relative motion or have a tendency to move relatively, have an obstruction phase along the tangential direction of the contact surface.

For the effect of sliding, this phenomenon is called friction; This force that hinders the relative motion is called frictional force.

Friction is a manifestation of electromagnetic force. Give birth.

Mechanics: 1. Interaction produces deformation;

2。The microscopic convex and concave surfaces of the objects produce mutual mechanical meshing;

3。Molecular bonding occurs.

The resistance to the mutual ploughing of the meshing parts and the shear action of the bonding joints is called friction force, which is the action of electromagnetic force.

Static friction. --Under the action of external force, if there is only a relative sliding tendency, and no relative sliding occurs, then this kind of obstructive effect is called static friction, and this hindering force is called "static friction". Static friction is not a fixed value, it changes with external force, and the critical value that makes the object change from rest to motion is called maximum static friction. Quiet.

The friction force can be any value between zero and the maximum static friction, i.e., zero sliding friction.

--When an object slides relative to another object, the frictional force generated on their contact surface is called sliding friction.

There is also a rolling friction that is generally not required.

Friction is the force that occurs when two non-smooth objects come into contact and move relative to each other, friction is a force of nature, which can be manifested as resistance or motion. You can't just say that friction is not good.

Friction can be divided into sliding friction, static friction, rolling friction, etc. See the textbook for details!

The essence of friction is electromagnetic force. The frictional force is generated due to the unevenness of the contact surface, and a part of the atoms of the two sides are trapped in the structural gap of the other and attract each other. Create resistance.

The static friction is relatively large because the contact surface between the two is larger. This is my personal understanding.

Friction is a physical force exerted on two surfaces when they are in motion with each other or have a tendency to move. Broadly speaking, objects are also subjected to frictional forces when moving in liquids and gases. As a metaphor, friction is also often used in everyday life to describe the forces that hinder progress.

Generally speaking, in table tennis, friction refers to the thickness of the contact between the surface of the table tennis ball and the racket, within a certain range, the thinner the friction, the lighter the friction, the thicker the friction should be strong, if excessive contact with the surface of the ball will produce the opposite result, the ball will be offset and cause undesirable consequences!

The frictional force of the three important forces – static friction.

There are three types of friction: static friction, rolling friction, and sliding friction. The magnitude of sliding friction is related to the magnitude of the roughness of the contact surface and the magnitude of the pressure. The greater the pressure, the rougher the contact surface of the object, and the greater the sliding friction generated.

Solution: (1) In 4 6 s, GB=27 N, both A and B move at a uniform speed, and the distance of A gliding to the left is S3=4 m

A is subjected to the tensile force of the horizontal rope F3 = (GB+G) 2= NWF3 = F3S3 = 74 J

2) In 2 4 s, gravity GB = 50 N, a glide to the left distance S2 = 2 MB descending distance H2 = S2 2 = 1 m

wgb=gbh2=50 j

Power p= wgb t2= 25 w

3) In 0 2 s, both A and B are stationary, GB=20 N, and the tensile force F1=(GB+G) 2=15 N of the horizontal rope lifting group

A is subjected to tensile force and static friction in the horizontal direction, and f1=f1=15 n is obtained by the equilibrium condition of the force

In 4 6 s, the equilibrium condition of the force obtains f3 = f3 = n from the title, and the magnitude of the sliding friction experienced by a in 2 6 s does not change.

Therefore, the sliding friction experienced by a in 2 4 s is large and small, and f2=f3= n

No, according to the condition of two-force equilibrium, when the object moves in a straight line at a uniform speed, friction = thrust, and once the object does not move in a straight line at a uniform speed (change of direction or acceleration), friction has nothing to do with thrust.

Also, when the force used does not push the object, the object is at rest, and the frictional force is equal to the thrust force according to the conditions of the balance of the two forces.

However, always friction and thrust are two forces that are opposite in direction and not necessarily the same magnitude.

The condition for the occurrence of friction is that there is a tendency of relative motion between two objects, so when there is a tendency of relative motion between a b, there is friction between a b, the magnitude is f = n, which is the friction coefficient, and n is the mutual pressure.

When is there no friction between a b? When there is no tendency of relative motion between a b, there is no friction between a b, for example, when a b and the inclined plane are in free fall together, all three are in a weightless state, and there is no friction between a b, and for example, when a b and the inclined plane are only subjected to the gravitational force perpendicular to the inclined plane in outer space, there is no friction between a b. For example, if a b is placed on a horizontal plane, there is no friction between a b.

The key to this type of question is how to determine whether there is a tendency towards relative motion, and my way of thinking is:

When two objects are in contact with each other, when they are relatively stationary, if there is no friction, the net force of the above object is not 0, then there is static friction, if there is no friction, the net force of the above object is 0, then there is no static friction, and the two objects slide relative to each other, and there is friction when there is pressure (or supporting force) between each other.

Increasing the friction in the horizontal direction has two meanings: first, it can increase the maximum value of the static friction provided by the ground when the object is subjected to a horizontal force, which is equal to the magnitude of this force and in the opposite direction, which is why the tighter the pressure is, the greater the force required to push the object; Second, it can increase the amount of resistance (sliding friction) provided by the ground when the object slides. The greater the pressure in the horizontal direction, the greater the ability of the wall to provide static friction, and the static friction provided by the wall only needs to be balanced with the gravity of the object, so the static friction remains unchanged.

Question 3: Gravity is proportional to mass, so when gravity and pressure are equal (horizontal placement, etc.), the gravity is proportional to the maximum static friction force from f= n, that is, the force you are talking about, and the conclusion is valid.