Why is it not uniform motion is not the magnitude of friction

You mean the situation of objects moving in a horizontal plane.

The gravity and support forces on the horizontal plane are balanced, and the forces in the horizontal direction are the tension and friction forces that affect the state of motion. The object is not moving in a uniform linear velocity, i.e. it is not in equilibrium (except when it is at rest without friction), and the force in the horizontal direction is unbalanced, i.e., the pulling force is not equal to the frictional force.

According to high school physics, friction is often divided into static friction and sliding friction.

The key point of difference is that if the force object of friction has a relative slide with the force object, the type of friction force is sliding magic friction force; Similarly, if there is no relative slippage between the two, then the type of friction is static friction. Of course, the premise is that there are conditions for friction between the two (1. there is elasticity between the two, 2. the contact surface is rough).

According to the above explanation, whether it is a uniform motion or not, as long as there is a relative sliding between the force object and the force object, it is a sliding friction force.

For the calculation, if it is a uniform motion, it can be solved by equilibrium knowledge or Hooke's law; If it is a variable speed motion, it can be solved by Hooke's law, and if the conditions are met, it can also be solved by mechanical equations (not equilibrium mechanical equations).

Your question has no logic and grammatical errors.

I'm guessing you mean that an object moving under the force of traction is equal to the magnitude of the sliding friction only when it is in a uniform linear motion, right?

Newton's laws tell us that an object with zero net external force will remain relatively stationary or move in a straight line at a uniform speed; The resultant external force exerted on an object moving in a straight line at a uniform velocity is zero. Since the state of motion of the object is constant and does not change, the force that opposes the traction force must be equal to its magnitude and opposite direction.

The horizontal force is unbalanced, and the pulling force is not equal to the frictional force.

1. Objects moving at a uniform speed will be subject to friction.

2. The object slides down at a constant speed along the inclined plane, and is subject to sliding friction.

In this process, the component and friction of gravity are balanced downward along the inclined surface.

3. The object is on an inclined conveyor belt.

If the object does not slide relative to the conveyor belt, then the component of gravity and friction along the inclined surface are also balanced in this process, but this friction is static friction.

1. Objects moving at a uniform speed will be subject to friction.

2. The object slides down the inclined plane at a uniform speed, and is subject to sliding friction, and the component force and friction force of gravity along the downward slope are balanced in this process.

3. The object rises at a uniform speed on the inclined conveyor belt, if the object does not slide relative to the conveyor belt, then the gravity is also balanced by gravity and friction along the inclined downward in the process, but this friction is static friction.

This is because, according to Newton's first law, if an object is in a state of uniform linear motion, then the net force on it is zero. Newton's second law describes the relationship between the combined external force and the acceleration of an object, i.e., f = ma (where f is the combined force on the object, m is the mass of the object, and a is the acceleration of the object). When an object is in a state of uniform linear motion, the net force to which it is subjected must also be equal to zero, since the acceleration is equal to zero.

In this case, be cautious that if the object is subjected to tension and friction, and the pulling force is equal to the frictional force, then the resultant force of the pulling force and the frictional force is zero. Therefore the frictional force can only be equal to the pulling force and cannot be greater than the pulling force, otherwise the object will no longer remain in a uniform linear motion and will start accelerating or decelerating. In addition, friction is not related to tensile force because the magnitude of friction depends only on the noise of the contact surface between two objects, the roughness of the surface, and the pressure during the relative motion between the objects, and not the magnitude of the tensile force.

The premise is that when "doing uniform linear motion", at this time, the object is in equilibrium and is subject to a balanced force, and when the two forces are in balance, the two forces are equal in magnitude.

Your understanding is correct:

When it just starts to move, the pulling force is greater than the frictional force, and at this time, the pulling force changes the motion state of the object; When there is a constant motion, the pulling force is equal to the frictional force.

The question is about "uniform linear motion", not just beginning.

Let's give you an example.

An object in a horizontal plane is moved in a straight line at a constant speed by a force of magnitude 120 n in the horizontal direction.

Because the forces are balanced, the tensile force is equal to the frictional force, i.e. the frictional force is equal to 120 N (the static friction force reaches the maximum, that is, the dynamic friction force).

If the tensile force is changed to 150n, the object will be accelerated.

Because the magnitude of the friction force is only related to the coefficient of friction, the magnitude of the pressure, and the area of action, and the three are unchanged in this question, the magnitude of the friction force is also unchanged, and it is still 120N (at this time, the friction force is the kinetic friction force).

If the pulling force is removed at this time, the object will decelerate, as above, and the direction of the friction force will remain unchanged at 120N

No!! When an object is not moving, if it is subjected to a tensile force, the frictional force is static friction.

Static friction is equal to tensile force, with the increase of tensile force, static friction is also increasing, until the maximum static friction is reached, until this time, the two forces are still balanced, the object is still in a static state, but the tensile force still has to increase, when the tensile force is greater than the maximum static friction force, the two forces are no longer balanced, that is, the tensile force is greater than the maximum static friction force, the object is not calm to the state of motion (accelerated motion state), once it moves, the friction force on the object is no longer static friction, but sliding friction.

At this time, the tensile force will be reduced to the kinetic friction force, and when the tensile force is equal to the kinetic friction force, the object will be balanced by the force and begin to maintain the speed at that moment, doing a uniform linear motion.

No!! Because it is already moving at a uniform velocity, the frictional force is only related to the pressure when it is moving. Even if the tensile force increases, the friction force no longer increases.

If the tensile force is increased and the velocity is still maintained, the tensile force will be equal to the frictional force, and the direction is opposite, if the object begins to do accelerated motion, the friction force is equal to the maximum static friction force fmax=un (u is the friction factor that is not moving, n is the supporting force facing the object) Xiao Lu Tong.

It is because an object will only move in a straight line with a uniform velocity when it is not acted upon by an external force.

When an object is not acted upon by an external force, it will maintain a uniform linear motion.

State. Frictional force.

It is also an external force. Once an object is subjected to an external force, it cannot maintain a uniform linear motion.

Therefore, if the state of motion of an object is a uniform linear motion, it must not be subjected to external forces.

Just a hypothesis.

To illustrate uniform linear motion.

The object is not affected by an external force. In fact, this is not the case.

In the actual situation, the uniform linear motion is the same driving force and frictional resistance, that is, the forward force and the resistance are equal, and the resultant force is zero, so the uniform linear motion is ensured.

Not necessarily, it only needs to be balanced.

Let's give you an example.

An object. on a horizontal plane.

Affected by the horizontal direction.

A force of magnitude of 120 N is used to move in a straight line at a uniform speed.

Because the forces are balanced.

So the pulling force is equal to the frictional force.

That is, the frictional force is equal to 120N (static friction.

Reach the maximum. i.e. dynamic friction).

If the tensile force is changed to 150N

Causes the object to move at an accelerated pace.

Because of the amount of friction.

only with the coefficient of friction.

The amount of pressure. area of action.

Again, this question. All three remain the same.

So. The amount of friction is also constant.

Still 120n (at this time.

The frictional force is the kinetic friction force).

If the pull is removed at this time.

then the object decelerates its motion.

Ditto. The magnitude of the friction remains the same.

120n

f=un When an object is moving at an accelerated motion on a horizontal plane and moving at a constant velocity, the dynamic friction factor u is the same as the positive pressure n, and the frictional force f is the same.