Block Definition and 998 Threads

A block of the periodic table is a set of elements unified by the orbitals their valence electrons or vacancies lie in. The term appears to have been first used by Charles Janet. Each block is named after its characteristic orbital: s-block, p-block, d-block, and f-block.
The block names (s, p, d, and f) are derived from the spectroscopic notation for the value of an electron's azimuthal quantum number: sharp (0), principal (1), diffuse (2), or fundamental (3). Succeeding notations proceed in alphabetical order, as g, h, etc.

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  1. EastWindBreaks

    Why is the output in the middle of the block diagram?

    (mentor note: not really a homework as the OP seeks understanding from an article) 1. Homework Statement I saw this on https://www.electronicshub.org/open-loop-system/, I thought the dry clothes should be the output, and heating the cloth should be the plant/process, I am so confused...
  2. M

    Conceptual Question: Block on a wedge on a frictionless surface

    Homework Statement This is more of a conceptual question, but say a block was set on top of an inclined plane, which was set on top of a frictionless level surface. Would the inclined plane move? Why or why not Homework Equations None The Attempt at a Solution My thought...
  3. J

    Forces on a Block and Friction on a Surface

    Homework Statement A 2.5 kg block is initially at rest on a horizontal surface. A horizontal force of magnitude 5.8 N and a vertical force are then applied to the block. The coefficients of friction for the block and surface are μs = 0.43 and μk = 0.24. (a) Determine the magnitude of the...
  4. sophia026

    Physics Homework -- block pressed against a wall is sliding....

    Hey! I've been trying to figure out these two problems but can't seem to get the right answer. Was wondering if someone could help me out? 1. A block is pressed against a vertical wall by a force F, as the drawing shows. This force can either push the block upward at a constant velocity or...
  5. C

    Change in the amplitude of a damped spring block oscillator

    Homework Statement A block is acted on by a spring with spring constant k and a weak friction force of constant magnitude f . The block is pulled distance x0 from equilibrium and released. It oscillates many times and eventually comes to rest. Show that the decrease of amplitude is the same...
  6. S

    Optical filter that blocks infrared and allows UV?

    Hello. I want to build camera for ultraviolet photography and reflectography. I plan to use debayer'ed backlit CMOS camera with or without Wood's ZWB3 glass UV filter. But I also need to find infrared cut filter because abudant IR radiation will ruin photos. Problem is that there are plenty of...
  7. J

    Finding the acceleration of a block of ice on a ramp

    Homework Statement A a block of ice with mass mA rests on a wedge of ice with mass mB=4.33 kg that is cut so that the surface of the wedge makes an angle of θ=38.1° with the ground. There is no friction between the pieces of ice or between the ice and the ground. At time t=0, the blocks are...
  8. karush

    MHB 307.8.3 Compute A^n for the Jordan block

    $\textsf{ Compute $A^n$ for the Jordan block $\displaystyle A=\begin{bmatrix} \lambda&0\\0&\lambda \end{bmatrix}$ and $n=1,2,3,4$ }$ $\textit{Make a guess on what $A^n$ will be for any $n$. }$ $\textit{Note: this matrix is not diagonalizable,compute the matrix powers by hand.}$ ok I think...
  9. alexi_b

    Find when the acceleration is 0

    Homework Statement A block of mass 2.42kg is accelerated across a rough surface by a rope passing over a pulley, as shown in the figure below. The tension in the rope is 13.9N, and the pulley is 12.3cm above the top of the block. The coefficient of kinetic friction is 0.395. (a: 2.28m/s^2)...
  10. L

    Find min/max accel. for block to stay on wedge (static fric)

    This HW problem due date has already passed. I had no problem with part a, but struggled thinking about parts b and c. I saw the solutions for parts b and c, but still don't exactly get it. I'll state the questions below, and tell you my way of interpreting the solution now. Could you tell me...
  11. Buckethead

    B Refined Interpretation of Relativity of Simultaneity?

    I have an image of the block universe that is probably similar to how many people view it, as a 4D non dynamical construct where the "present" is a slice of this block and this slice moves forward from the past to the future. Furthermore, depending on your relative velocity, your slice may be...
  12. Qmechanic18

    Which block will strike first? Left or right?

    1. A block of Mass 'm' is connected to another block of Mass '2m' through a weightless pulley by a weightless inextensible thread of length 2l. The left block(mass=2m) rests on a table at a distance l from its edge, while the right block is kept at the same level so that the thread is...
  13. DaveC426913

    Eigenstates, Block equations, Regge-theories

    PF has gotten so far over my head, I keep expecting to see this: :frown:
  14. N

    Optical Where to get some VIS block, NIR pass plastic sheets?

    I'm talking about nealy black plstic in front of some remote controls to add to my similar DIY device. https://i.imgur.com/lmL4XN5.png I found some plexiglass that does this (blocks visible light, let's NIR pass) but the thinnest is 2mm so I don't think it is usable for this because is...
  15. navneet9431

    B Will Block M2 Move Left? Understanding Forces in a Connected Spring System"

    Suppose two blocks m1 and m2,connected by a spring are kept on a frictionless surface and the block m1 is applied an external force F. My teacher taught me that in a spring the force is generated in the direction opposite to the displacement of the spring. So the spring would generate a force...
  16. navneet9431

    How could the block A move to the left corner?

    Homework Statement See question number 5. Homework Equations F=m*a W=F*s Uniform acceleration motion equations The Attempt at a Solution Actually,I am having some difficult understanding the problem. See the F.B.D of the system, see the friction is acting on the block in the forward...
  17. T

    Fluid static problem with wooden block being pulled down

    Homework Statement The figure below shows a metal object (2) hanging by a thin cord from a floating wooden block (1). The wood block has a SG of 0.3 and dimensions of 50mm x 50mm x 10mm. The metal part as a volume of 6600m^3. Find the mass of the metal part and the tension in the cord. Work in...
  18. nineteen

    Why was the F block of the periodic table created?

    Basically, the F block is a series in the periodic table that consist of elements that are artificially synthesized. My question is, why were these elements synthesized? What was the need of synthesizing such elements?
  19. navneet9431

    When Friction the block m2 start to move?

    Homework Statement A block m2 is placed on a surface where the coefficient of friction is μ2 and another block m1 placed over the block m2 where the coefficient of frictio is μ1. A force F=k*t(Force as a function of time),is acting on the block m2. Now my question is that when would the...
  20. stoky

    Do car windows and windshields block ultraviolet light?

    I'm curious if car windshields / windows block UV (ultraviolet) light, the one from either the sun, or UV flashlights, like the Convoy S2+ Nichia 365nm.
  21. prakhargupta3301

    What will be the acceleration of a 10kg block w.r.t. the ground frame?

    Homework Statement [/B]We have to find acceleration produced by 10 kg block on 5 kg block with respect to the ground. Downward acceleration of life is 5m/s-2 Homework Equations f=ma g=10m/s The Attempt at a Solution Effective force at play on 10 kg block: mg- ma...
  22. Alyssa Eiger

    Length a Block on Pulley Moves - (Basic Energy Question)

    Homework Statement Two masses are connected by a string that is passed over a massless pulley. At t=0, the 6-kg mass is moving upwards at 2m/s, while the 4-kg mass is descending at the same speed. How far will the 6-kg mass rise before it stops? Homework Equations KE= 1/2*m*v^2 PEg: m*g*h...
  23. H

    A Is Block Spin Still ±1 in Ising Model?

    When one applies block spin scheme on Ising model, what's the value for block spin? If we set the average value for spin in a block, it should not be ±1 anymore. But if so, is the transfer matrix is still two dimensional?
  24. U

    Question Concerning The Coefficient of Friction: Block on a Rough Inclined Plane

    Homework Statement A block of mass 20kg is on rest on a rough plane inclined at 60 degrees to the horizontal. A force P is applied to the block to "maintain equilibrium". P is parallel to the line of greatest slope of the inclined plane. The maximum value of P is twice the minimum value of P...
  25. J

    Optics: Image formed from a glass block

    Homework Statement Homework EquationsThe Attempt at a Solution I have solved this problem . For that I had to use refraction at the first surface , then reflection from the back side and then again refraction from the first surface . This gives me the correct answer . But when I saw the...
  26. R

    What is the velocity of the block pulled by strings

    Homework Statement :[/B]In the arrangement shown in the figure, the two ends P and Q of the light unstrechable string move downward with uniform speed u as shown. The upward speed of the mass m is v. Then which of the following is correct: A) v cos60°=u B) 2v cos60=u C) v =2ucos60 D) v= u...
  27. cooldudeachyut

    Friction problem for two block system on an inclined plane

    Homework Statement Two block M1 and M2 rest upon each other on an inclined plane. Coefficient of friction between surfaces are shown. If the angle θ is slowly increased, and M1<M2 then Options : 1- Block A slips first. 2- Block B slips first. 3- Both slip simultaneously. 4- Both remain at...
  28. isukatphysics69

    Find the initial speed of a block before it hits a spring

    Homework Statement Homework Equations W =ΔKE The Attempt at a Solution found work done by spring -1.3 =ΔKE -1.3 = KEFINAL - KEINITIAL -1.3 = .5(0.25)(VFINAL2) - .5(0.25)(VINITIAL2) Since v final is 0 since it stops momenteraly at the bottom of the spring -1.3 = - .5(0.25)(VINITIAL2)...
  29. Beblak2

    Elastic collision of block on block

    There is 4 parts to this one question. A 2.0 Kg block is traveling to the right with a velocity of 3.0 m/s. The block collides with a stationary 1.0 kg block and the blocks bounce apart (elastic collision). 1. Homework Statement (a). if the velocity of the 1 kg block is +4 m/s after the...
  30. isukatphysics69

    Find the acceleration of a block on an inclined plane with a pulley

    1. Homework Statement picture Homework Equations f=ma The Attempt at a Solution Below is my attempt for part B, i am not sure what i am doing wrong here but my answer is off for acceleration
  31. jybe

    Block moves down incline, hits spring, find spring constant

    Homework Statement [/B] The block, initially at rest, slides down the ramp and compresses the spring 0.03 m. Theta = 30 degrees L = 1.25 m M of block = 2 kg Δx = 0.03 m 1) Write the expression for the initial and final energy states 2) Find the spring constant K Homework Equations mgh...
  32. isukatphysics69

    Find acceleration between two blocks (bottom block)

    1. Homework Statement Problem in pictures Homework Equations f=ma The Attempt at a Solution So the tension force is 20N, i took the frictional force on the bottom of the block as 3*9.8*.4 because the bottom of the block has a total mass of top block and bottom block = 3kg, so i have 20N -...
  33. isukatphysics69

    Block pushed up against wall, determine the force of friction

    1. Homework Statement I have already solved this one weeks ago, and i have a test Tuesday so i was reviewing these problems. I understand everything when solving with 60N as the force.. but then when i changed the force to 20N, i had to use the coefficient of kinetic friction to get the correct...
  34. Johns24

    Normal force of a block with a massless rope

    Homework Statement Mass of block: 19kg Applied force: 225N at 16 degrees to accelerate block from rest Coefficient of static: 0.55 Coefficient of kinetic: 0.30Homework Equations Unknown The Attempt at a Solution I have solved for parallel tension and perpendicular tension Tperp =...
  35. isukatphysics69

    Find the frictional force between a block and a wall

    1. Homework Statement A block weighing 22 N is pushed against a vertical wall by a force of magnitude 60 N directed 30° above the horizontal. The block is intitally at rest. The coefficient of static friction between the wall and the block is 0.55 and the coefficient of kinetic friction between...
  36. J

    Work done by friction on smaller block

    Homework Statement Homework EquationsThe Attempt at a Solution If the two blocks were to move together when the external force of magnitude mg is applied , the acceleration would be mg/3m = g/3 . This acceleration would have to be provided by friction . Value of friction should be mg/3 . But...
  37. E

    Acceleration of a block on a massive pulley

    Homework Statement A block of mass MB = 0.7 kg hangs from a string wrapped around a hoop that can rotate around its center. The hoop has a mass of MH = 1.3 kg and a radius of R = 0.4 m. The block descends under the influence of gravity. What is the magnitude of the acceleration of the mass in...
  38. F

    Electric flux through a wedge shaped block

    Homework Statement Homework Equations - The Attempt at a Solution Flux on opposite sides = 0 The answer is (E) , right ?
  39. E

    A frictionless incline with a block sliding down it....

    A frictionless incline (the triangle below) is bolted to the floor so that it can not move. A block of mass m slides down the slope, which makes an angle with the horizontal.a)Draw a free-body diagram for the block, labeling all forces uniquely. b)Describe all the forces listed above in the...
  40. Richie Smash

    What is the speed of block as it reaches O from point P

    Homework Statement A 0.5 Kg block slides from rest down an inclined plane as shown in the figure. The velocity at the bottom of the plane is 6 m/s. The vertical distance PO is 2m. (gravity = 10m/s2 If the block were to be dropped from P, what would be the velocity at O? Homework Equations K.E=...
  41. A

    What is the volume of a block of silver that weighs 107 N

    How to find the volume of a block of silver that weighs 107 Newtons
  42. nomadreid

    How can a partial dopamine agonist block dopamine pathway

    I am looking into Aripiprazole. I am not a medical professional. I am confused by the descriptions of it in Wikipedia: (a) It is a partial dopamine agonist; i.e., it acts like dopamine to stimulate nerve cells, and (b) It is an atypical antipsychotic, i.e., it blocks dopamine (and serotonin)...
  43. S

    Maximizing Friction Coefficient for Block on a Wedge: A Calculus Approach

    Homework Statement A block of mass m is placed on a rough wedge inclined at an angle α to the horizontal, a distance d up the slope from the bottom of the wedge. The coefficient of kinetic friction between the block and wedge is given by µ_0x/d, where x is the distance down the slope from the...
  44. R

    Pushing down on a block at an angle on a horizontal table with friction

    Homework Statement Example 2.12 : A block pulled on a horizontal table with friction. A block of weight 100 Newtons rests on a horizontal table. The coefficient of static friction between the block and the table is µs = 0.8. a. If someone pulls on the block with a force F in the direction 37◦...
  45. AbbeyC172

    Calculate the work required to move the block

    Homework Statement A man weighing 180 lbf pushes a block weighing 100 lbf alone a horizontal plane. The dynamic coefficient of friction between the block and plane is 0.2. Assuming that the block is moving at a constant speed, calculate the work required to move the block a distance of 100 ft...
  46. T

    Unit Vectors and Momentum Changes in a Block of Ice

    Homework Statement A 0.5 kg block of ice is sliding by you on a very slippery floor at 2.5 m/s. As it goes by, you give it a kick perpendicular to its path. Your foot is in contact with the ice block for 0.0035 seconds. The block eventually slides at an angle of 24 degrees from its original...
  47. J

    Time period of block springs SHM

    Homework Statement Homework EquationsThe Attempt at a Solution Length of the unstretched springs is L .Suppose block is pushed towards C by a small distance x . This causes a change in length of springs B and C . Their new length is L+∆L .Consider spring B. If the new length makes a small...
  48. F

    Conservation of Energy: block on a table

    Homework Statement Homework Equations ∑F=ma W = - ΔUs ΔUs = 0.5 k (xƒ)^2 - 0.5 k (xi)^2 W = ΔUs + ΔKE d = viy t + 0.5 * t^2 * a The Attempt at a Solution A) [/B]W = - (0.5 k xƒ^2 - 0.5 k xi^2) = - (0-100) W = 100 J B) W = ΔUs + ΔKE 100 = 0.5 m vf^2 -0 + 0 - 0.5 k xi ^2 100 = 0.5 * 2 * vf^2...
  49. R

    Modified Block Problem -- Block on top and on the side

    << Thread moved to the schoolwork forums from the technical forums, so no Homework Template is shown >> The problem is a modified version of two basic block problems. This is my work so far, but I end up with two equations for acceleration from m1 and m2, I don't understand how to use both...
  50. Alexanddros81

    A block is released from rest, determine its velocity

    Homework Statement 14.10 Solve Prob. 12.47 by the work-energy method 12.47 When the 1.8-kg block is in the position shown, the attached spring is undeformed. If the block is released from rest in this position, determine its velocity when it hits the floor Homework EquationsThe Attempt...
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