How to calculate the superimposed friction between two objects
Publish: 2021-04-28 19:27:39
1. The acceleration of the object below is affected by the friction of the upper surface and the lower surface. The friction of the upper surface is equal to the friction of the object above, and the direction is opposite. The friction of the lower surface is related to the gravity of the two objects (that is, the pressure on the table). Then the acceleration can be obtained by analyzing the stress of the object below
2. Let's assume that a force you said is applied to a,
,
b is driven by A.
(
or a force acts on B, a is driven. Anyway, not both of them are & quot; A force
there is an acceleration process from static to constant speed. In this process, the driven object is driven by the friction between two objects.
when the constant speed is maintained, there is no friction between AB and the driven object. The resultant force of the driven object is zero and the driven object moves at a constant speed.
If AB moves at a constant speed together, the driven object accelerates under the friction between ab, And friction = mass of the object to be carried * acceleration
,
b is driven by A.
(
or a force acts on B, a is driven. Anyway, not both of them are & quot; A force
there is an acceleration process from static to constant speed. In this process, the driven object is driven by the friction between two objects.
when the constant speed is maintained, there is no friction between AB and the driven object. The resultant force of the driven object is zero and the driven object moves at a constant speed.
If AB moves at a constant speed together, the driven object accelerates under the friction between ab, And friction = mass of the object to be carried * acceleration
3. The direction of friction between two objects is the opposite direction of the relative motion or relative motion trend of the two objects. Friction hinders the relative motion of the object. Don't look at the absolute motion of the two objects, just look at their relative motion. For example, if you pull the object to the right, the friction it receives is to the left
4. It can be regarded as a whole without considering the internal friction
or it can be taken out separately for analysis
depending on the specific situation
or it can be taken out separately for analysis
depending on the specific situation
5. The situation of not moving: the lower friction force is opposite to the direction of the force ~ ~ moving, relative static: the upper friction force is opposite to the direction of motion ~ ~ remember, the friction force is opposite to the direction of the force, it is to make the object as static as possible
6. According to the state of motion and Newton's second law. If the state remains unchanged, the force is analyzed to find the balance force with the friction force. If the state changes, after force analysis, judge the force according to the generated acceleration.
7. If it's just stacked horizontally, suppose the weight of the upper object is G1 and the weight of the lower object is G2, then the friction between the two objects can be calculated by the formula: F= μ N= μ G1 Friction with the ground: F= μ N= μ( G1+G2)
8. Unknown_Error
9. For a, the force is balanced, and the friction f = f direction is left
the forces are mutual, for B, the friction f = f direction is right
the forces are mutual, for B, the friction f = f direction is right
10. High school stage mainly master two kinds of friction: sliding friction, static friction. Concept: when there is relative sliding or relative sliding trend between two objects in contact, the object is subject to the force that hinders the relative sliding or relative sliding trend. Understanding: the friction when there is relative sliding is sliding friction, and the friction when there is relative sliding trend is static friction. Understand the word "relative" well, and contact these two objects as the reference frame of each other; The sliding trend is that the two objects want to slide, but they don't actually slide. Assuming that the surface is smooth, the force analysis is carried out. If the two objects slide relatively after the surface is smooth, the sliding trend of the two objects can be judged
One Size:
sliding friction: preferred formula: F = UFN, dynamic friction coefficient multiplied by positive pressure, can also be solved according to the combination of forces (the resultant force in equilibrium state is 0, f = ma in variable speed state)
static friction: can only be calculated according to the combination of forces, the size has nothing to do with positive pressure
the maximum static friction is approximately equal to sliding friction, But the essence is greater than sliding friction. The maximum static friction is the upper limit of static friction. If the required static friction exceeds the maximum static friction, relative sliding occurs between objects< 2. Direction:
1. The direction of friction is opposite to the direction of relative sliding or the direction of relative sliding trend. Pay attention to the study of friction when finding relative sliding. These two objects are mutual reference system
2. Direction of friction when objects are stacked: if two objects have the same speed in the same direction and the speed is not the same, the friction that the fast running with high speed is resistance, It is opposite to the movement direction; Small velocity is driven by friction, and the direction of motion is the same. If one has speed and the other has no speed, the object with speed is a fast running object, and the friction is resistance, which is opposite to the direction of motion; Objects without speed are driven by friction. If two objects are stacked and have the same speed, when judging whether there is static friction, it depends on whether the two objects have acceleration, and then specifically judge whether static friction is needed to provide acceleration
friction is a difficult part of mechanics in senior high school, which can only be briefly introced in this paper. If you have specific problems, I can help you analyze them.
One Size:
sliding friction: preferred formula: F = UFN, dynamic friction coefficient multiplied by positive pressure, can also be solved according to the combination of forces (the resultant force in equilibrium state is 0, f = ma in variable speed state)
static friction: can only be calculated according to the combination of forces, the size has nothing to do with positive pressure
the maximum static friction is approximately equal to sliding friction, But the essence is greater than sliding friction. The maximum static friction is the upper limit of static friction. If the required static friction exceeds the maximum static friction, relative sliding occurs between objects< 2. Direction:
1. The direction of friction is opposite to the direction of relative sliding or the direction of relative sliding trend. Pay attention to the study of friction when finding relative sliding. These two objects are mutual reference system
2. Direction of friction when objects are stacked: if two objects have the same speed in the same direction and the speed is not the same, the friction that the fast running with high speed is resistance, It is opposite to the movement direction; Small velocity is driven by friction, and the direction of motion is the same. If one has speed and the other has no speed, the object with speed is a fast running object, and the friction is resistance, which is opposite to the direction of motion; Objects without speed are driven by friction. If two objects are stacked and have the same speed, when judging whether there is static friction, it depends on whether the two objects have acceleration, and then specifically judge whether static friction is needed to provide acceleration
friction is a difficult part of mechanics in senior high school, which can only be briefly introced in this paper. If you have specific problems, I can help you analyze them.
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