![](data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 72 71" width="72"></svg>)
What is the relationship between flux and divergence? I know the unit of flux is mol / (m ^ 2 · s). What is the unit of divergence? Can you explain them in detail?
flux divergence
definition:
Let P, Q and R be functions defined on a certain spatial region, and let, be dynamic vectors dependent on independent variables, which are called vector functions defined on, or vector fields defined on
2 is also set as the directed surface in, which is the unit normal vector at the upper point, so it is called the flux (or flow) of the vector field (or vector function) passing through the specified side of the curve
3 is called the divergence of vector field (or vector function)
Who can explain the difference and connection between flux and divergence
Let P, Q and R be functions defined on a certain spatial region, and let, be dynamic vectors dependent on independent variables, which are called vector functions defined on, or vector fields defined on
2 is also set as the directed surface in, which is the unit normal vector at the upper point, so it is called the flux (or flow) of the vector field (or vector function) passing through the specified side of the curve
3 is called the divergence of vector field (or vector function)
First aid: high school physics friction exercise car to human friction? 2. As shown in the figure, the mass of the trolley is m, the mass of the person is m, and the person pulls the rope with a constant force F. if the person and the vehicle remain relatively stationary, excluding the mass of the rope and pulley and the friction between the vehicle and the ground, the friction between the vehicle and the person may be: (the pulley is on the left) A、0 B. (M-M) f / (M + m), direction right C. (M-M) f / (M + m), direction left D. (M-M) f / (M + m), direction right I think it's ACD, but some say it's CD and some say it's C. please give me more advice! Regardless of the friction between the car and the ground, the figure shows that people are on the car, the rope crosses the fixed pulley and is horizontally connected with the car, and the pulley is on the left side of the car How can we explain it in terms of movement trend? The mass of the trolley is m, excluding the mass of people. The mass of people is m. why choose C?
The combined external force to the left of the horizontal direction of the human and vehicle system is 2F, which is obtained by Newton's second law
2F＝(M+m)a
The tension F of the rope to the person and the static friction F of the vehicle to the person (set to the right), then
F-f=ma
f=F-ma=(M-m)F/(m+M)
If M = m, f = 0;
If M > m, then f = (M-M) f / (M + m), the direction is to the right;
If M
If the friction between all objects suddenly disappears, which of the following phenomena cannot happen () A. A car stationary on a level road cannot start B. The breeze can move the train on the track C. I can't write with a pen in my hand D. A man can leave the earth with a gentle jump
A. The car rubs the ground backward by the wheels. At the same time, the ground will give the wheels a forward force to make the car move forward. Therefore, if there is no friction, the car stationary on the horizontal road cannot start;
B. If the train has no friction in the horizontal direction, the wind energy along the track will blow the train;
C. When writing, if there is no friction, the pen will slide down from the hand, resulting in inability to write;
D. Any object near the earth is affected by the earth's gravity, so people can't leave the earth when they jump up, which has nothing to do with friction
Therefore, D
The car runs at a constant speed on the highway, the traction force is 1500N, and the friction force on the car is - friction force? The size is -? When the traction force increases to 2000N, the friction force is - N? (the title doesn't say uniform speed.) (by the way, the relationship between rolling friction and traction force)
The vehicle runs at a constant speed on the highway, the traction force is 1500N, and the friction force on the vehicle is rolling friction. The friction force is 1500N
When the traction force increases to 2000N, the friction force is 1500N. Here, the friction force has nothing to do with the traction force, and the vehicle makes uniform acceleration
A physics problem about friction A long light wood board is placed on the smooth horizontal ground, and two blocks a and B with mass of Ma = 1kg and MB = 2kg are placed on the wood board. The dynamic friction factors between a and B and the wood board are μ= 0.2, the horizontal constant force F acts on block a, (acceleration by gravity g = 10m / S2). Then: () A. if f = 1n, the block and board will remain stationary. B. if f = 1.5n, the friction force on block a will be 1.5nc. If f = 4N, the friction force on Block B will be 4nd. If f = 8N, the acceleration of block B will be 1.0m/s2. The answer is d. can you help me analyze in detail why the overall method is used for block a and B, Can static friction be ignored?
This is to calculate the critical condition
For a, when a just slides with the board
fa= μ mAg=2N
Because it is light wood, m board is ignored
fb= μ mBg=4n＞2N
Therefore, B does not slide with the board
F = 2n
A = f / M = 1m / s2
Therefore, when a slides with the board, the acceleration of B is 1
If it does not slide, FA = f thrust. At this time, AB is relatively stationary, and the overall method can be used
RELATED INFORMATIONS
- 1. Why is the friction force and traction force of a car moving in a straight line at a uniform speed the same? Instead of traction greater than friction? The equilibrium force of a stationary object is equal. Why is the equilibrium force of uniform linear motion equal?
- 2. Super difficult physical problems -- on sliding friction Can the work done by sliding friction not make a single object generate heat! My example: There is a block on a wood block on the ground. There is a friction coefficient between the block and the block, while the block has no friction with the ground. When the block is pulled by force, the block and the block will slide relatively, If the block is taken as the research object and the sliding friction makes positive work on the block, the block will not No internal energy increased? (heat transfer between blocks and wood blocks is not considered) My basis is: sliding friction does negative work and internal energy increases So sliding friction is a measure of the increase in internal energy when work is done to change internal energy Therefore, the internal energy increases only when the sliding friction does negative work (regardless of heat transfer) When the sliding friction does positive work, the internal energy cannot be increased If I am wrong, please give me a reasonable explanation I have another point to consider: the wood block generates heat, but the object block does not generate heat. If the object block and the wood block are insulated, only the wood block becomes hot, but the object block is not hot Your explanation was wonderful, but I still don't understand it. Can you be more precise? Thanks again to the two and future friends
- 3. Derivative (1)y=2^sin(1/x) (2) Y = ln (x ^ 2 + A ^ 2 under x + radical) (3) Y = (x / 2) x [under the root sign (a ^ 2-x ^ 2)] + (a ^ 2 / 2) x (arcsinx / a) (a > 0) These are compound functions, which is the process of setting the function as a whole
- 4. What does 1000F mean in the expression? string resultValueString = resultValue.ToString(); if (resultValue == 1000f) { ******} What is the interpretation of "1000F" in the above expression?
- 5. Let the function f (x) be continuous on the symmetric interval [- A, a], and prove that ∫ - A, a) f (x) DX = ∫ (0, a) [f (x) + F (- x)] DX
- 6. It is known that f (x) is an even function defined on R, and the odd function g (x) = f (x-1) defined on R, then the value of F (2009) + F (2011) is () A. -1 B. 1 C. 0 D. Unable to calculate
- 7. It is known that the even function f (x) with the definition domain R is an increasing function on [0, positive infinity], and f (1) = 0, then the inequality XF (x)
- 8. Let f (x) be an even function defined on R. when x < 0, f (x) XF '(x) < 0 and f (- 4) = 0, the solution set of inequality XF (x) > 0 is
- 9. What are the concepts and differences between inflection point and stagnation point?
- 10. What does this symbol mean in advanced mathematics? For example, when x → 0, 1-cos (x √ 1-cosx) ~ 1 / 2 x ^ 2 (1-cosx) has ~, what does it mean? Is it equivalent to? Or what? For an answer, thank you!
- 11. High school physics electromagnetism formula
- 12. Let f (x) be a continuous function and prove that x f (T) (x-t) DT on ∫ lower 0 = ∫ lower 0 and upper x (∫ lower 0 and upper t f (U) Du) DT
- 13. Using P-Q decomposition method and Newton Raphson method for power flow calculation, which is the faster convergence speed
- 14. If the acceleration direction of the vehicle is consistent with the speed direction, when the acceleration decreases, then () A. The speed of the car also decreases B. The speed of the car first decreases and then increases C. When the acceleration decreases to zero, the car comes to a standstill D. When the acceleration decreases to zero, the speed of the car reaches the maximum
- 15. What is the geometric meaning of the gradient representation of a binary function? Seeking envelopment····
- 16. Higher number derivative problem (derivative) stem "f (x) = x ^ 3-3ax ^ 2 + 2bx
- 17. come Set in (a, b), f '(x) = g' (x), then the following formulas must be true? A.(∫f（x）dx)’=(∫g（x）dx)’ B.∫f’（x）dx=∫g’（x）dx I know a is right, I can't understand it, or B. that expression doesn't make any sense at all?
- 18. If the function y = f (x) is differentiable in the interval (a, b) and x0 € (a, b), then lim f(x0+h)-f(x0-h)/h h->0 The value of is?
- 19. It is proved that the function f (x) = LNX / X is an increasing function on (0, e)
- 20. Let the function f (x) be second-order differentiable on the interval [0,1], and f (0) = 0, f '' (x) > 0. It is proved that f (x) / X is a monotonically increasing function on (0,1]