The following pairs of forces belong to the balance force () A. The gravity of textbooks and the support of textbooks to desktop B. The pressure of the textbook on the desk and the support of the desk to the textbook C. The gravity of textbooks and the support of desktop to textbooks D. The gravity of the table and the support of the ground to the table Is d wrong? I think CDs are all right

First of all, let's review the knowledge points
If two forces are equilibrium forces, they must satisfy the following requirements: 1. Acting on the same object; 2. Equal in size; 3. Opposite in direction; 4. In the same straight line
A. Wrong. [textbook has no support for desktop, only pressure]
B. Error. [condition 1 not met]
C. Correct. [all four conditions are satisfied]
D. Error. [the support force of the ground to the table = the gravity of the table + the gravity of the book, so condition 2 is not satisfied]

What are the symbols of tension, traction, resistance, friction, buoyancy, gravity, pull, support and pressure? What are their concepts?

Tension F, traction force F, friction force F, buoyancy are usually marked as f. buoyancy, gravity g, supporting force N, and pressure are also F. these physical quantities are usually marked with corner markers in order to distinguish them,
Pulling force is the force exerted on an object by the outside world. Traction force is the pulling force of a machine. It is named after the pulling force. Friction force is the force formed by an object moving on the ground. It is opposite to the pulling force. If it moves in a straight line at a constant speed, it is equal to the pulling force (two forces are balanced). Buoyancy is the force given by liquid, and the formula density is X G x V immersion. Gravity is the gravitational force given by the earth to the object
I am now in the third year of junior high school attached to Peking University. I am confident that my physical level is OK. This is my answer. I hope to adopt it!
Wish you progress!

The force that does not belong to elasticity is a. supporting force B. pressure C. gravity D. tension

】Ask a junior three about the relationship between the balance force of pressure, upward tension, gravity and supporting force I would like to ask a body to remain at rest on the horizontal plane. At this time, there is a pulling force vertically upward, but less than the gravity of the object. At this time, the object still remains at rest. Why? There is another question, in this question, which forces are the balance force, and which forces constitute the combined force. I asked the above questions randomly. If I ask them wrong, I will forget

All problems need to grasp one point: carefully analyze the force on the object
A static object is subjected to vertical gravity, vertical upward tension, and vertical upward support force. Under the action of three forces, the force balance is the balance of three forces, that is, the upward pulling force. The upward supporting force is equal to gravity, so it is static. These three forces are balanced, and any two forces are unbalanced. Any two forces can be combined, The resultant force is balanced with the third force

What are the symbols of "tension, pressure, support, power, resistance, friction, and gravity"?

F. P, N, f dynamic, f resistance, F, G

What letter is used for supporting force, friction force and tension force

Commonly used in physics are as follows:
Gravity: G
Support: n (sometimes f)
Friction: F
F: Tension

Gravity, pressure support The difference between The connection and difference between pressure, gravity, friction, supporting force, tension, resistance, attraction and power Who and who is a pair of balance force when doing the question

Pressure and gravity are two different forces. On the horizontal plane, it can only be said that the value of pressure is equal to gravity, but not pressure and gravity. In inclined plane and horizontal plane, pressure is different. Gravity is generated by gravity, and on different planets, the gravity of objects is also different
Friction is the force that hinders the movement of objects, and it is also an indispensable force in life
Support force is the force given to an object by a horizontal plane
Resistance is the force that blocks the movement of an object, and it can also be power
Such as the earth, magnet, attractive, junior high school does not require to master
Such as tension, thrust, etc. belong to pulling force

Gravity, support and pressure I know the relationship between them. But why is this relationship? First of all, the point of action of the supporting force is on the surface of the object, but the gravity is on the center of gravity of the object, so it is not on the same object? How is the equilibrium force? I still think that the point of action of pressure and gravity is the balance force? What are the three elements of the supporting force, The second line above is wrong, it should be "so and not on different objects?" In addition, the supporting force of the object on the slope seems to be different from that of gravity. In this case, isn't it a balance force? There is also a question: the gravity of physics textbooks and the support of desktop to physics textbooks are a pair of balance forces. This option is the cause of error. What should we say?

It's on the same object
The so-called balance force refers to several forces that make the body in a state of equilibrium. Therefore, there is a definition to know that the condition of meeting the balance force is: two forces are equal in size, opposite in direction, in the same straight line! At the same time, we can know from the first that several forces are acting on the same object, that is, the objects under force are the same!
The body under pressure is different from that of gravity, so it is not a balance force!
The three elements refer to the size, direction and action point of the force
It seems that the supporting force of an object on an inclined plane is different from that of gravity, because the direction of gravity is always vertical downward, while the direction of supporting force is perpendicular to the surface of the object. At this time, their directions are not in the same straight line, so they are not balanced forces
The design of the questions is not complete. It does not indicate whether the desktop is level or not

How to find the decomposed force? For example, gravity = support force + pressure. Why do we solve the decomposed force like this? Why is it that some forces do not need to be + or subtracted, but can be solved directly by trigonometric function f * cos or f * sin?

It depends on the object you are studying. If two objects are stacked together, object a is on the top and object B is on the bottom. If you analyze object B and take object B as the research object, B is subject to gravity, the force of object a on B (that is, pressure) and B is supported by the ground to B. therefore, when analyzing the object, you should know what the object is, and then look at the effect of the object in contact with the object to be analyzed, Then we can solve it by making a balance equation

Is it correct to say that the pressure on the horizontal plane of an object resting on the horizontal ground is equal to its gravity?

No~
If the body is subjected to other vertical forces, it is obviously not equal