I have some problems with mechanics and friction in high school, and I definitely have to chase poin

There is no relative sliding with the ground--- and the analysis of steamed dumplings along the inclined plane and the vertical inclined plane is it.

Vertical inclined plane acceleration = 0 n = mgcos

Along the inclined plane f=ma and f= n f= gcos 2The direction of the sliding friction is always along the surface and opposite to the direction of the relative motion (there is no doubt about this): along the inclined face downward.

m g does not change, n does not change.

The bevel does not move. There is no difference between an inclined plane and a fixed "hillside" in the physical model.

If the inclined motion to the right is another model, depending on the nature of the motion of B.

For example, if the ground is smooth, b will accelerate to the right, and its trajectory will not be the original inclined line.

And to become a diagonal line with a larger inclination angle--- you may wish to set this angle as At this time, the support force n = mgcos The support force decreases -- but the friction force along the surface The support force is still perpendicular to the surface.

There's no doubt that it's just that it's not inclination, it's just an inclination.

1. How to analyze and solve the friction during this period? 2. Direction of friction.

First of all, the friction force must be along the inclined plane downwards for the inclined plane, and for A, it is along the inclined plane upwards, opposite to the direction of motion. Second, you have to make sure that the horizontal component of the friction force experienced by the inclined plane on it cannot be greater than the friction of the ground on the inclined plane, and this should be equal because the inclined plane is stationary.

3. Is the support constant? I remember how it was like when there was acceleration, the support would change.

The supporting force on object A is certainly constant, that is, it is opposite to the equal magnitude of the component of g along the direction of the perpendicular inclined plane, so the inclined plane is also unchanged, and the force is reciprocal.

4, 》What else?

1. The frictional force of a is facing down along the inclined plane, which is opposite to the direction of motion; The frictional force experienced by B is horizontally to the left, opposite to the horizontal direction of motion of A;

2. Treat A and B as a system, A is in a weightless state, and the supporting force is smaller than the gravitational sum of the two.

1. The friction given by b is directed to the left along the slope of the mgucos b to the left because the system has an acceleration to the left 3. The support force does not change, it is smaller than the gravitational force of A plus B, because the acceleration of the system does not change and the downward support force changes when accelerating, it should be the situation that the system is subjected to an external force, and the external force changes, or for some reason (for example, the previous inclined plane is different from the u of the next section) is that the friction between A and B has changed, ps These two situations overlap, write so seriously, of course, the mass should be proportional to the composition.

In your other way of thinking, frictional workmanship = friction force * opposition displacement, so it is still point Q, the work done by force = force * counterpart displacement in the direction of force.

The block moves counterclockwise on the conveyor belt and finally lands at the q point, and the block moves horizontally to the right throughout the process, showing that the acceleration of the block is to the right.

When the block is on the conveyor belt, the balance of gravity and support force cancels out, and the block is only affected by friction in the horizontal direction, since the acceleration direction is to the right, then it is inferred that the friction direction is to the right, and at this time the conveyor belt is moving counterclockwise, imagine that the movement trend of the conveyor belt is to the left (because it is counterclockwise) and the friction direction is to the right, and the actual displacement of the block is naturally smaller than the original, which is just in line with the amount of work and kinetic energy change done by friction, so it is naturally not contradictory.

Work done by friction = friction x relative displacement.

This is indeed the work of friction.

But it's not a quick job of friction teams.

Work done by friction = Friction x relative position = Work done on the block + Transformed internal energy?

aThe object is subjected to gravity, support, friction along the inclined surface.

The B object is subjected to gravity, ground support force, ground friction, friction of object A (up along the inclined plane), positive pressure of object A (perpendicular to the inclined plane).

To calculate the magnitude of friction, the angle q of the bevel plane and the coefficient of sliding friction u are also required.

Frictional force of an object, n mgcosq

f nu u*mgcosq, down the inclined plane.

The object B is subjected to the frictional force of A F nu u*mgcosq, and the ground friction force is applied to B along the inclined direction upwards, and the support force of the tip of the inclined plane is unchanged.

1.From what you mean, b should be an inclined plane, and this problem can be solved in sections:

1. When A slides up from the bottom of the inclined plane, the force analysis of A is carried out: A is subjected to gravity, the elastic force of the inclined face of A, and the friction force, because A is sliding up along the inclined plane relative to B, so the friction force should be opposite to it, so the friction force is downward along the inclined plane.

2 Later, when A decelerates to zero, it depends on the relative magnitude of the static friction force and the gravity force along the inclined plane, if the former is greater than the latter, then A stops on the inclined plane, the friction force goes up along the inclined plane, the magnitude is equal to the component of gravity, if the latter is greater than the former, then the object has to move downward, according to the nature of the frictional force, therefore, the friction force is along the inclined plane, and the magnitude is less than the component until it slides back to the ground.

2 Cf. above. 3 The supporting force does not change, because the component of gravity does not change, so the pressure of A on B does not change, so the frictional force does not change.

When you say that the support force will change, it should be that the support force of the ground facing the inclined plane will change.

The length of the wooden board l, the mass of the wooden board and the wooden block are m, as shown in the figure with a light rope and the fixed pulley are connected, first with the constant force of the size f to the right of the wooden board for a period of time bending and arguing, and finally the wooden block just did not slide down the wooden board, the pulley has no friction, and the rest of the friction factors everywhere, the action time of the force t

The current questions are missing, and at least 80% of the questions in the college entrance examination will not get a full score.

The error-prone point of this problem lies in the judgment of whether the rope has tension after withdrawal and the conversion of sliding friction and static friction in the later stage.

According to f=ufn. Know the friction formula. Then fn=mg.

In the case of the same fn. The larger the u, the greater the f. where u is the coefficient of friction.

fn is positive pressure. So the first question is that on a runway with a completely smooth surface, then you are the same. Old.

Both shoes have as much friction.

According to the above formula, the same shoe runs on the uneven surface, due to the different friction factors between different shoes and the run; That is, you are different, so the uneven bottom surface of the shoe receives more friction.

1 The frictional force depends on the pressure and the coefficient of friction, moving with the same force, and the two forces are balanced.

2 The same shoes are equal on a runway with an uneven surface.

1. There is as much friction as possible. Although there is no such surface and no shoe, it is an ideal state that it is generally believed that as long as one side is completely smooth, there is no friction with other objects.

2. With the answer to the first question, this question is obviously that the uneven shoe has a lot of friction, because the other shoe is smooth and has no friction with the runway.

A shoe and track have one (or two) smooth and are not subject to friction, so the first two cases are the same friction.

The second question is incomprehensible, but you should be able to push it out according to A.

1 is the same as 2 is more uneven.

For the analysis of the force of A, the force of A is balanced, so the resultant force is zero, so A cannot be subjected to external force in the horizontal direction, that is, there is no friction between A and B.

For the analysis of B, B has a relative ground sliding to the right, so B is subjected to the sliding friction of the ground horizontally to the left.

The relative velocity of ab is 0, and there is no relative motion.

Don't you choose them all, it's AD

The key point of this problem is the maximum static friction f, the static friction between the objects is less than the maximum static friction and will not move, then when the two objects of ab are moving, the friction received by the b object on the rise is less than f, that is, the acceleration of ab is less than a=f mb, so the total force received by ab is less than (f mb)*(ma+mb), and the result is: 3f

The maximum static friction between AB is F, so the maximum acceleration of B is F M, if AB does not slide relatively, then AB acceleration is the same, and the maximum is F M, so F=AAB*(MB+MA)=F M*3M=3F