How to deduce the formula of buoyancy?

Take cube as an example. According to the fact that the pressure in liquid is equal in all directions and proportional to the concentration
The forces acting on four of the six surfaces of the cube in the liquid except the upper and lower surfaces cancel each other
Upper bottom force F1 = ρ GH1 * s, lower bottom force F2 = ρ GH2 * s
Buoyancy = resultant force = f2-f1 = ρ g (h2-h1) * s = ρ GV = liquid gravity
(v = (h2-h1) * s cube volume, ρ GV = liquid and gravity equivalent to cube volume)

What are the expressions of physical buoyancy in grade two

F float = g row = ρ liquid GV row (Archimedes principle) = ρ liquid GV object (immersion) f float = f up-f down f float = G-F pull (use a spring dynamometer to lift an object into the liquid surface) f float = g object (float or suspend) f float = g object-n branch (sink) calculate the buoyancy of a ship: F liquid = P (liquid density) g V (discharged body

Calculation formula of buoyancy of water
How much buoyancy does a copper block bear when it sinks into the water? F = () n
And what does g = 10N / kg mean

F = P water GV row g = 10N / kg is the weight of 1 kg body is 10N

How to judge the number of rope segments by pulley block?
As shown in the figure, please tell me how to judge whether odd even setting is applicable,
PS: Junior High School
What if that's the case?

It's not suitable to use your "odd even fixed". The above two numbers are two segments. In fact, using your "odd even fixed" method is not as easy as using my method. The method is as follows: you separate the moving pulley, and then count the number of segments of the rope directly connected with the moving pulley

How to draw the number of fixed pulley and movable pulley of pulley block
I know odd even fixed, but I don't know how to draw the number of moving and fixed pulleys
There should be a formula, isn't there? It's better to have that formula. It's easy to fill in the blanks

In fact, just remember 3 points (the previous answer is too general) 1. Take the moving pulley or fixed pulley as the starting point (odd even fixed) 2. From the inside out. 3. Do not cross. That's OK, just draw

What is the number of strands of the rope in the fixed pulley and movable pulley block in leverage?
It's best to explain it with pictures. Give a few more examples

Method 1: look at the picture. As long as the rope in contact with the moving pulley is included, the rope with the fixed pulley is not used (because the moving pulley saves labor and the fixed pulley changes direction) as shown in the figure below. From left to right, it is 2354 method 2: look at the physical quantity given in the title. If the distance s of the rope moving and the distance h of the object rising are known, then n = s / h

The number of rope segments of the pulley block depends on how many strands of rope are connected with the movable pulley. Is the segment connecting the movable pulley also included?
I hope my friends with better physics can answer this question. After all, perfunctory or random answers are not very good behaviors
If you are satisfied, you will get extra points according to the situation

Don't count the rope between the moving pulley and the object. Just look at the rope around the pulley block. A few strands of the rope are in contact with the moving pulley

Are several strands of rope n on the pulley block movable or the whole pulley block
You cover all the pulleys below, leaving only one pulley above. If you see a few ropes, there are several strands of ropes
If there are several movable or fixed pulleys, is that true

Just look at the pulley and check the number of ropes
Sometimes the fixed pulley is more than the movable pulley, and the one with more is not labor-saving

If there is a pulley block with more than two movable pulleys, the number of strands of the rope shall be determined according to which movable pulley

Look at the pull direction of the rope, the direction is up, the number of strands of the rope = 2n + 1. The direction is down, the number of strands of the rope = 2n (n is the number of pulleys)

Junior high school physics knowledge
What is Newton's first law?

Newton's first law of motion
Content of the law
English Name: Newton first law of motion
Without any external force, any object always keeps in a state of uniform linear motion or static state until it is forced to change this state by external force
Since the property of keeping a body in motion is called inertia, Newton's first law is also called inertia law
English Name: Law of India
Inertia is the inherent property of all objects, whether solid, liquid or gas, whether the object is moving or stationary, it has inertia
[edit this paragraph] description
Newton's first law, also known as the law of inertia, scientifically clarifies the two physical concepts of force and inertia, correctly explains the relationship between force and state of motion, and puts forward that all objects have the property of keeping their state of motion unchanged inertia, It is a basic law in physics. The above-mentioned law is mainly derived indirectly from astronomical observation. It is an abstract conclusion, which can not be directly verified by experiment simply according to literal definition. The statement closer to the actual situation is that when the resultant force of external force on any object is zero, the original state of motion will remain unchanged, that is, the original static will continue to be static, The inertia of an object is essentially the inertia of the object relative to the translational motion, and its size is the inertial mass. The object also has inertia relative to the rotation, but it is not the same as the inertia mentioned in the first law. Its size is the moment of inertia. Both the inertial mass and the moment of inertia are used to express the inertia, but they are different physical quantities, There is no term of moment of inertia in middle school physics. It is unnecessary to mention the difference between the two. Whether an object is still or moving in a straight line at a constant speed without external force or with zero external force depends not only on the reference system, but also on the initial state of motion
Newton's first law explains two problems: (1) it clarifies the relationship between force and motion. The motion of an object does not need force to maintain. Only when the state of motion of the object changes, that is, when acceleration occurs, the action of force is needed. Based on Newton's first law, the qualitative definition of force is obtained: force is the action of one object on another, (2) it puts forward the concept of inertia. The reason why a body keeps still or moves in a straight line at a constant speed is that it is not forced, It is determined by the characteristics of the object itself. The inherent characteristics of the object that keep the original state of motion unchanged are called inertia. The uniform linear motion of the object when it is not under force is also called inertial motion. Newton did not explain in the first law that the static or moving state is relative to what frame of reference, Newton's first law is established in such a frame of reference. Generally, the frame of reference in which Newton's first law is established is called inertial frame of reference. Therefore, this law actually defines the important concept of inertial frame of reference, It has special significance, and is an indispensable independent law among the three laws. The first law can not be regarded as a special case of Newton's second law. Note: force is not the cause of velocity, but the cause of acceleration!
The formation of Newton's first law
(1) Galileo's research and scientific imagination:
The same car starts to slide down from a standstill at the same position on the same inclined plane (this is to ensure that the car has the same speed when it reaches the horizontal plane). The first time a towel is laid on the horizontal plane, the car stops after a short distance on the towel (as shown in figure a); the second time a smooth cotton cloth is laid on the horizontal plane, The car glides far on the cotton cloth (as shown in Fig. b); the third time is smooth wood, and the car glides the farthest (as shown in Fig. C)
Galileo thinks that it is the resistance of the plane to the car that makes the car stop. The smoother the plane is, the farther the car will slide. It shows that the smaller the resistance is, the farther the car will slide. Galileo scientifically imagines that if a very smooth plane can be found and the resistance is zero, the car's sliding speed will not slow down
(2) The complement of Descartes
Descartes and others conducted a more in-depth study on the basis of Galileo's study. He believed that if a moving object is not affected by any force, not only the speed will not change, but also the direction of motion will not change, and it will move at a constant speed along the original direction
(3) Newton's great contribution
Newton, a great British scientist, summed up the research results of Galileo and others, and thus summed up an important physical law: all objects always remain at rest or moving in a uniform straight line when they are not under the action of force. This is Newton's first law
The discovery and summary of Newton's first law
More than 300 years ago, Galileo analyzed similar experiments and realized that the less resistance a moving object receives, the slower its speed will decrease and the longer its time will be. He further reasoned that in an ideal situation, if the horizontal surface is absolutely smooth and the resistance of the object is zero, its speed will not slow down, It's going to move at a constant speed forever
Galileo had studied this problem, Newton once said: "I am standing on the shoulders of giants to succeed." this sentence is aimed at Galileo. So Newton summed up the results of previous studies, summed up the famous Newton's first law
Newton's first law is obtained by analyzing facts, further generalizing and reasoning. Although it is impossible to verify this law directly by experiment, all inferences from the law have withstood the test of practice. Therefore, Newton's first law has become one of the basic laws of mechanics. Force is the cause of acceleration

How to deduce the formula of buoyancy?