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. shivajikobardan

    MHB Confusion on motion estimation block diagram-MPEG video compression-:

    https://lh4.googleusercontent.com/g6wQjnQ6p3IVt86-_kwnNVwyOb_iUxUXWChyf0XZR5PO17uOnPbNhCxdpfUSScvU8sAR8Al2FNRMoeMEqLUUuJsvGOSnpFO94tutB2h-927rxVYRDUGzi-JF9FYs9hKivGdCvrAP My doubts are as follows-: -> Why frame n is not segmented to blocks? -> Why no inputs from (n-1) side for block matching...
  2. rudransh verma

    What is the minimum force needed to move a block with friction present?

    We know the minimum force to move the body in presence of friction will be ##F>\mu F_N## But it’s not right.
  3. F

    Pulling down on the string connected to a whirling block on a table

    At the time of release, the equation of motion of blocks A and B T-m_ag = m_aa and T=m_b\omega^2R respectively, where T is the tension in the string. Solving for the acceleration a then gives a=\frac{m_b\omega^2R - m_ag}{m_a}. Not sure what I did wrong or what incorrect assumptions I made...
  4. Y

    Forces applied to a block on a ramp

    hey I am really hope for some help becuase i don't know what I am doing wrong, the angle of the first part is 21.801. here is my solution i would like to know what I am doing wrong
  5. H

    Sliding resistance of eccentrically loaded block

    Summary:: What is the sliding resistance of an eccentrically loaded block on a flat surface? If a 1000kg block is placed on a flat surface (say coeff. of friction = 0.4), what force does it take to slide if it loaded eccentrically, i.e. at the far edge of the block? My thinking is there is...
  6. rudransh verma

    A block coming down the incline

    ##W_{ext}=mgh+KE_f+0=-20(5\sin 37)+(1/2)2(10^2)## ##W_{ext}=-60.18+100=39.81J## But it’s not consistent with ##W=F.d=20*5=100J## I can’t figure it out.
  7. rudransh verma

    Block pulled up the incline problem

    a) $$v=u+at$$ $$v=0+(F/m)t$$ $$v=-10$$ Now $$v^2=0+2as$$ $$s=-5$$ $$W=F.d=(-20)(-5)=100J>40$$ b) $$W=-mgh$$ $$W=-20(3)$$ $$W=-60$$
  8. Tea_Aficionado

    A block falling onto a spring (SHM related question)

    EDIT for clarity: I solved the question, just asking for if the explanations make sense and if the mechanical energy is considered to be conserved before and after the collision due to reasons listed below the photo. I hope this image is readable (grr, scanner is janky). I'm guessing the...
  9. rudransh verma

    To move a block up to the top of the wedge

    I think on top of the wedge the KE of both the wedge and block will be same but this fact doesn't take me anywhere. The base length of the wedge is not given. Maybe that would have helped.
  10. VVS2000

    I Block sliding down an incline plane

  11. S

    I In what formation does this simple block universe exist?

    This is just a rough estimate of what a simple bock universe might be to an observer in the red worldline on the left side, and what it is to an observer in one of the blue worldlines in the graph on the right side. In the graph on the left side, two blue objects moved past the red object very...
  12. F

    B Block universe theory question

    Hello, can somebody help me out please? just watched this video so far understood but if motion changes the now frame its logic if the alien cylcles to the guy sitting that his time is slower and the guys time will be in the future (time delitation). but when the alien is moving away how can...
  13. H

    Bound charges of a block (top and bottom surface)

    From what I think, to find the bound charges of a block on the top and bottom surface I have to find the electric field or the displacement (D). However, I'm not sure how to proceed with a cube. For example, with a sphere ##E = \frac{Q}{4\pi \epsilon_0 r^2}## since r is constant. For a cube, it...
  14. P

    The velocity of a movable block that is penetrated by an arrow

    This problem is in a chapter on momentum in the book basic engineering mechanics explained. Help me Mario
  15. Eclair_de_XII

    Is it Appropriate to Include More Than One Prose-Dialogue Pair in Each Block?

    ***Title should read: ``Is it appropriate to include more than one instance of a prose-dialogue pair in each prose-dialogue block?'' instance of `prose-dialogue pair'? I don't know what they're called, actually, so I'll give an example of what I mean. "Hello Bob," said Sally. "How is the...
  16. T

    COVID Cannabinoids Block Cellular Entry of SARS-CoV-2 and variants

    At least in the lab. Abstract: https://pubmed.ncbi.nlm.nih.gov/35007072/ Full article: https://pubs.acs.org/doi/10.1021/acs.jnatprod.1c00946
  17. S

    Problem of spring block system: force vs conservation of energy

    I have used the work energy theorem like all source have shown me an have arrived at the right answer where work one by all the forces is the change in kinetic energy -1/2kx^2 - umgcosΘx +mgsinΘx = 0 is the equation which becomes -1/2kx -umgcosΘ+ mgsinΘ = 0 where k= spring constant u=...
  18. D

    Magnitude of force acting on wedge and block

    Clearly if ##F = 0## and ##\tan\theta > \mu_s##, then using the above equations for ##f_s## and ##n##, we get ##f_s > \mu_s n## so the block will slip. However, it seems that as long as the force ##F## is directed to the right with a certain minimum magnitude, namely ##\frac{\tan\theta -...
  19. S

    I Universal Block Theory: Free Will

    Mostly about free will
  20. S

    Finding acceleration of block with block on top, connected by rope

    I have already concluded that the way to solve this problem is through (20 N - (3 kg * 9.8 m/s^2 * 0.16) - (2*(1 kg * 9.8 m/s^2 * 0.16))) / 3 kg I have several questions: Why do we multiply the second set of parentheses by 2? Why do we count the friction between the 1 kg box and the 2 kg box...
  21. Buckethead

    B Paradox in the block universe interpretation

    Consider two observers, Alice and Bob, standing on the Earth together with synchronized clocks. Bob asks Alice, “Is this now?” to which Alice replies, “Yes, it is”. They are clearly both in the present moment. Bob climbs a mountain and some time later, due to the lower gravitational field...
  22. S

    Can countries effectively restrict access to VPNs and censor internet usage?

    A product often advertised on YouTube videos about politics is a VPN service. On thing that a VPN service supposedly does is allow you to use the internet in one country yet appear to be a user in a different country. This let's you bypass country specific restrictions. Are countries that...
  23. D

    Maximum force applied to prevent block from sliding up ramp

    I tried using Newton's first law as the net force in both the x and y directions should be zero in this case. In the free body diagram you need to consider weight, friction, normal force, and the horizontal force. I got a result that said that the horizontal force F you apply is at most W(mu_s +...
  24. J

    Gage Block Physics: Is It Understood?

    Does anyone know if the Gage Block physics is now understood?
  25. grandpa2390

    Block on a Spring, Nonconstant Net Force

    Just to be clear, this isn't a homework problem. it is an example problem found on page 68 of the text "Matter and Interactions" 4th edition. The solution is given in the book, but I'm having difficulty following their reasoning. according to the book the net force is not constant, therefore we...
  26. K

    Virtual displacement for a block sliding down a wedge

    A block slides on a frictionless wedge which rests on a smooth horizontal plane. There are two constraints in this system. One that the wedge can only move horizontally and another that the block must remain in contact with the wedge. We want to find the virtual displacements for the two block...
  27. H

    Engineering Control block diagram's transfer function

    The ac signal is converted to DC signal which is connected to a capacitor to filter the DC signal. The filter DC signal is step down for 12volt to 5 volt using a voltage regulator. The regulated DC signal is connected to a crystal oscillator that converts the DC signal to a square wave signal...
  28. Ebi Rogha

    A Block universe and entropy increase

    I wonder how physicists who support this theory explain the increase of entropy?
  29. B

    Block diagram showing how to turn white noise into rain

    So I have been looking and trying different thing to synthesize rain noise like this: https://mynoise.net/NoiseMachines/campingRainNoiseGenerator.php but I cannot get it. and the graph that this sound makes did not help at all: can some make a block diagram of how to do this?
  30. B

    Boundary condition: null traction on the boundary of an elastic block

    Hi everyone, I'm trying to understand the rationale behind the boundary condition for the problem "Finite bending of an incompressible elastic block". (See here from page 180).Here we have as Cauchy Stress tensor (see eq. (5.82)): ##T = - \pi I + \mu (\frac{l_0^2}{4 \bar{\theta}^2 r^2} e_r...
  31. B

    Finite bending of an elastic block - Equilibrium equations

    I am studying the finite bending of a rubber-like block, assuming Neo-Hookean response. In the following, ##l_0##,##h##, ##\bar{\theta}## are parameters, while the variables are ##r## and ##\theta##. The Cauchy stress tensor is ##T= - \pi I + \mu(\frac{l_0^2}{4 \bar{\theta}^2 r^2} e_r \otimes...
  32. K

    Iron block dropped into a container of water sitting on a scale

    Does the scale change during the block sinks? I am so confused... Is there any difference on change of scale with the applying of drag force?
  33. B

    Extension of an elastic block of Neo-Hookean material

    I'm studying elasticity from classical Gurtin's book, and my professor gave us the following example, during lecture. Unfortunately, this is not present in our references, so I'm posting it here the beginning of the solution, and I will highlight at the end my questions. First I need to state...
  34. LulyPop

    Engineering Energy and friction -- Can the block make it all the way up the ramp?

  35. H

    Calculate the block mass in an equilibrium system with two supports

    The attachment is the key. I wonder where the (3/8)L comes from. Can someone explain it, please? Thanks.
  36. jskrzypi

    Spring launches a block up a ramp -- How far does it go?

    I think I have all the pieces here, and am able to solve for a work through the air. But I have a power output, and don't know how to isolate it to find the distance.
  37. T

    Some Common Meds Block SARS-CoV-2 Attachment to Cells

    Open access. https://www.nature.com/articles/s41586-021-03491-6 A more approachable synopsis at: https://www.news-medical.net/news/20210412/Tapeworm-infection-drug-blocks-SARS-CoV-2-damage-in-the-lungs.aspx Cheers, Tom
  38. M

    Determine how many bolts are needed to secure a block of steel

    I work in injection molding and I am looking to make some sort of standard for how many bolts are needed to secure what we call a "manifold spacer block". We are constantly battling each other about blocks being under or over secured, and as a manufacturing engineer, I am interested in knowing...
  39. Pipsqueakalchemist

    Engineering Questions on Forces & Friction: Analyzing Plate & Block Motion

    So I have questions on two separate questions. The first question is about the fbd of the plate attached to the pin. How can there be an Ax since there’s no other force in the horizontal direction wouldn’t the plate start moving on the x-direction due to imbalanced forces. Second question about...
  40. W

    Is the 680J mentioned in this problem a red herring?

    Am I right in thinking the 680J thing is a red herring? Even using the author's method of "same work required in either case" (ie =mgh in both cases) we still end up cancelling h and getting $$F=\frac{mg\sin \theta}{\cos \phi}\ge mg\sin \theta=320$$ etc. I.e. no need for 680J. Maybe I am wrong?
  41. icesalmon

    Engineering Determine the transfer function of the block diagram

    Step 1: I first started by reducing the inside of the block diagram of picture "bd" (the portion with G1 and the negative feedback G2) I obtained G1/[1 + G1G2] I'll call this term "F" Step 2: Then I'm left with two terms feeding into a summing point: F - G3 I'll call this term "K" I can...
  42. Pipsqueakalchemist

    Engineering Dynamics help: Block on a wedge on an incline (frictionless surfaces)

    So I’m having trouble with relative motion with moving inclines and I literally can’t find any help online and my prof does a lot of these problems. This is one of my homework problems, can anyone help me with it please.
  43. J

    Finding the normal force of a block under water, under pressure

    So since the block is at the bottom there's no pressure pushing it up. To calculate the mass and force of gravity, I multiplied the density of the block by its height and cross sectional area and got 564 kg. Multiplying this by 9.8 I got the force of gravity of 5527.2 N. Now to find the force...
  44. Hamiltonian

    Dropping a block on another block which is performing SHM

    at the mean position of the original block, its velocity is ##V = \omega A## once the new block is dropped we can conserve momentum in the horizontal direction $$m\omega A = (2m)v$$ $$v = \frac{\omega A}{2}$$ where ##v## is the common velocity of the blocks. but if instead of conserving linear...
  45. ayans2495

    Calculating initial temperature of iron block submerged into water

  46. I

    I Block Time & Action at a Distance

    Sorry, for the lack of correct terminology - this may be answered elsewhere on the forum, I haven't been able to find it. If the Universe is in Einstein's 'Block Time', then does this provide a mechanism for 'action at a distance'? Rather than a particle being split and entangled, if viewed...
  47. P

    A Eigenvalues of block matrix/Related non-linear eigenvalue problem

    I have a matrix M which in block form is defined as follows: \begin{pmatrix} A (\equiv I + 3\alpha J) & B (\equiv -\alpha J) \\ I & 0 \end{pmatrix} where J is an n-by-n complex matrix, I is the identity and \alpha \in (0,1] is a parameter. The problem is to determine whether the eigenvalues of...
  48. J

    Finding the maximum velocity and PE of the block between 2 springs

  49. X

    Free inclined plane and a block sliding on it

    Hi, I'm missing something really stupid here... The problem is the usual one with a block sliding down (or moving up, it should be the same) a frictionless inclined plane,which itself is free to move on a orizontal frictionless surface. These problems are usually solved stating that only...
  50. A

    Calculating Temperature Change in the Bullet and Block Problem

    I think that the kinetic energy is equal to heat right. Mv^2 / 2 = ms delta T Delta T is 0,64 But I don’t really know if the temperature decreases or increases at the end
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