What is Block: Definition and 999 Discussions

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. goodOrBad

    Finding Minimum A for Equilibrium in a Two Block Problem

  2. goodOrBad

    Block A Reaches Equilibrium: 92N Force

    I tried to solve it via equilibrium equations and I got 92N for block A
  3. T

    Calculating the Force Required for a Moving Wedge and Block System

    The entire mass of the wedge is ##(M+m)## therefore ##F=(M+m)a##. The forces acting on the small mass are its downward weight ##mg## and the normal force with the contact of the wedge therefore I got that ##N=mg\cos\theta##. Similarly the horizontal component is ##N=ma\sin\theta## therefore...
  4. T

    Calculating Time with Forces Acting on a Block

    When drawing a diagram of the forces acting on the block, I have the following forces: $$\sum F_x = a_x = (g \sin\theta) \cos \theta .$$ Now, I can use the following kinematic equation $$x=vt+\frac{a_xt^2}{2}$$, where $$v=0$$ and $$a_x = (g \sin\theta) \cos \theta$$ $$\therefore \frac{2x}{t^2}...
  5. Elias_HH

    Engineering How to draw a block diagram of a discrete element with its impulse response

    Hello friends, I have a problem with a exercise sheet. Given is the impulse response of a discret element. The task is to draw the block diagram. But I think that the solution in the sheet is wrong. Because based on the difference equation (Exercise.pdf) there should be 3 delay elements. I have...
  6. T

    How do you calculate the acceleration of a block sliding down a plane?

    When drawing a diagram of the forces acting on the block, I have the following forces: $$\sum F_x =mg\sin\theta = ma$$ $$g\sin\theta = a$$ however the solution has $$F_x = ax = (g \sin\theta) \cos \theta$$ but I am not sure how they got that? I know the normal force is $$N=mg\cos\theta$$ but the...
  7. Hamiltonian

    Two block problems with friction

    the maximum value of friction between the surfaces of the blocks is ##60N## the friction should be self-adjusting until this maximum value. Hence the force of friction in the given scenario should be = 30N but this is physically impossible as if this is the case the top block will be at rest and...
  8. Hamiltonian

    Why Does the Friction Force Not Match in the Two Block Problem?

    when a force of 10N is applied to the 4kg block the force of friction between the two blocks will also equal 10N as the maximum value of friction between the two surfaces is f = N##\mu## = 20N. if you look at this free body diagram f = F = 10N so the net force acting on the top(4kg) block will...
  9. Hamiltonian

    Block on a wedge connected to pulleys

    if the tiny block moves downward by an amount x, the wedge should also move forward by the same amount x as they are connected by the same string whose length has to remain constant, (by differentiating it wrt time we get speed) hence I concluded that v1 = v2, but my book says otherwise what is...
  10. R

    Why does the big block accelerate?

    Clearly, in the picture I can see that on the small block on top, tension and gravitational force act. Gravity gets balance by the normal force, so tension is the only force causing acceleration. On the block at the side gravity and tension result in vertical acceleration. However, I do not...
  11. burian

    Two blocks on a third block which is split into two ramps

    So, for this question first I did a free body diagram in the perpendicular x-y axes, and, I got some equations with the normals, but the answer is independent of normal forces. So, I'm not sure how to eliminate the two normals. Further I find it quite weird that big block-A doesn't come into the...
  12. Petext

    Momentum Problem -- Bullet fired into a block of wood

    A gun is fired vertically into a block of wood(unknown mass) at rest directly above it. If the bullet has a mass of 24.0g and a speed of 310 m/s, how high will the block rise into the air after the bullet becomes embedded in it?
  13. Leo Liu

    Normal force acting on a block on an accelerating wedge

    We have a wedge whose surface is ##\theta## from the horizontal surface. After a block is placed on its frictionless slant surface, the wedge starts to accelerate due to a force F. What is the normal force acting upon the block? I have been trying to solve it but I got no clue. Could someone...
  14. Leo Liu

    A block on an accelerating wedge

    For question b, the official solution sets up a non-inertial coordinate on the block and writes out the following two equations: $$\begin{cases} \begin{align*} f\cos(\theta)+N\sin(\theta)-mg=0 \qquad \hat\jmath \\ N\cos(\theta)+f\sin(\theta)=ma \qquad\quad\;\;\, \hat\imath \end{align*}...
  15. ItsukaKitto

    Maximum height a block reaches after separating from a curved moving ramp

    Diagram attached at the endI personally think there's something wrong with this question, and I'd like if someone can tell me whether it's the question that is wrong or my approach. If I attempt the solution thinking that M should be stationary, the solution is simple. 0 - 1/2 mv^2 = -mgh...
  16. kyphysics

    Does Ad Block Plus No Longer Work On Google Platforms?

    I used to successfully block ads on YouTube with ABP. Now, I'm seeing them. Could I have a virus? Or, does ABP simply not block stuff on Google/Alphabet platforms anymore?
  17. Mahfuz_Saim

    Will the pebble meet with the block according to the given condition?

    Question 1: I have used v= Aω*cos(ωt+δ) where A= 0.2 m, ω= π/3, t=1 and δ=0. Are the values right in this case? I am confused. Question 2: From question 1 I have got the value of V which is 9 m/s. By using v= ω√(A^2-x^2), I have got the value of x. Now, do I need to add it with 2.5(distance...
  18. LCSphysicist

    A block and a disk connected by a rope

    Basically, there is a gravitational field g and a friction force acting on the cylinder, which does not slip in the plane. The question is, the acceleration of m'. I solve this question basically by this: " m*g*dh*sina + m'*g*dh = m*v1*dv1 + m'*v2*dv2 + I*w1*dw1 " {1} w*r = v1' + v2' So The...
  19. LCSphysicist

    Block bombarded by particles {colision}

    I thought i could apply a conservation of momentum in this case, Apparently, this is not right, so i don't know what to do now.
  20. Z

    Find the angle required for a 3kg block to slide down an incline

    This is a rough sketch of the model. It is frictionless. I originally tried simple right-angle trig (sin θ =opp/hyp), but that just ends up as sin θ = sin θ , as well as cos θ = cos θ. I feel like there's also a way to manipulate dynamic equations around to equate something that is capable...
  21. L

    Engineering Block Diagram Reduction - Control System

  22. rakailee

    Truck with attached inclined plane and a block on the incline

    I tried solving this by assuming the acceleration of the truck and block to be the same so the block would stay on the incline. Also, I would assume truck ma = static friction, block ma = mgsintheta... then I solved for a to plug into 1st equation to get 12990 N. Is this correct? I wasn't sure...
  23. Lynch101

    I Conflict between the Block Universe and Bell Tests?

    Usually questions I have of this nature are down to my limited understanding of the concepts, and this may be no different. Based on my understanding of the Block Universe interpretation of relativity, it appears to me as though there is a conflict between Bell tests and the Block Universe. To...
  24. Lynch101

    B Unlearning the Block Universe: How Relativity Challenges Our Perception of Time

    Just a heads up, this post is quite long. I've tried to be as detailed as possible from the outset because I find it can help avoid the need to clarify things later, or helps when clarifying things later. There is only one question posed at the end, but I think it might be useful to read the...
  25. K

    Help with acceleration -- A block on top of a block on a frictionless table

    I don't understand the problem. Does not block A and B make a system, so they should have the same velocity and acceleration at all time? If not, why do they have different accelerations? I don't understand this part of the problem either: "pull applied to block B equals 12.0 N, then block B has...
  26. E

    Friction force of 2 connected block on steel surface

    hello there, I am wondering if my attempt at a solution for this particular problem correct?? I mean I know that the blocks won't move and the total friction force is 38.95N (at least lesser than that, since that is the maximum static friction). I saw someone attempted the solution but it is...
  27. Like Tony Stark

    Equations of motion of a block on a spinning wedge

    I think that the only force acting on the wall is the normal force caused by Coriolis force, so it can be calculated this way: ##N=m2\dot r \dot \theta## But ##\dot r## is not constant, so how can I calculate it? Then, I can't calculate the acceleration either since I don't have the value of...
  28. brotherbobby

    Pulling with and without a pulley

    Let me draw a free body diagram for the man. I assume that for both cases (a) and (b), the man pulls the block up with uniform velocity. (1) In case (a), realising that the man is in equlibrium (##\Sigma F = 0##) the normal reaction on the man ##N_a = w_M + T## is given by ##N_a = (50+25)\times...
  29. domingoleung

    Simple Mechanics Problem -- Block connected to a wall by a rope

    (So this is the system given) The following is my analysis: (i) (ii) Well, my problem is - I got a negative acceleration and its quite impossible to have block B moving to the left. So I am wondering if there are any mistakes I've made.
  30. IamVector

    Cylinder rolling with a block inside it

  31. domingoleung

    How to Calculate Bullet Velocity After Penetrating a Block

    Change in KE = Change in thermal energy 0.5 * (6)* vblock^2 = 0.4 * 6 * 9.81* 0.1 vblock = 0.885 By Conservation of Momentum, (0.05)(854) = (0.05)*vbu + (6)(0.885)I am not sure whether Change in KE = Change in thermal energy is true coz there should be a change in internal energy of the block...
  32. IamVector

    Analyzing Forces in Three Rods and a Block Problem

  33. T

    Calculating Work and Kinetic Energy on an Inclined Plane

    Summary:: I have done parts a-d but I can't seem to get e correct! A 6.10 kg block is pushed 9.00 m up a smooth 38.0 ∘ inclined plane by a horizontal force of 78.0 N . If the initial speed of the block is 3.20 m/s up the plane. a. Calculate the initial kinetic energy of the block. (found...
  34. IamVector

    Hard kinematics problem: Block pushed onto a moving conveyor belt

    stuck on this question
  35. S

    Python: inverse of a block matrix

    I am using the following code. It's returning the block matrix (Z) raised to negative one (think about inputting 22/7 in a Casio fx-991ES PLUS). import sympy as sp from IPython.display import display X = sp.Matrix([[1, 1, 1], [2, 2, 2], [3, 3, 3]]) i = sp.Matrix([[1], [1], [1]]) Z =...
  36. A

    Work-energy principle for a block fired up a vertical track

    I know how to solve the problem but have a question related to it. When the block is initially released from the spring the spring, having been pulled back, should give an initial velocity to the block. In that case why is the block's initial velocity zero?
  37. Kaushik

    General electronic configuration of the d and f block elements

    Is it ##(n-1)d^{1->10}ns^2 \ or \ (n-1)d^{1->10}ns^{0->2}## ? My textbook says it is the latter. But I feel like it should be the former. Moreover, period 6 and 7 has the presence of f-orbitals. So adding## (n-2)f^{0->14}## would make it more general. Isn't it? And also what about the f-block...
  38. V

    Velocity of a 1-kg block after it has dropped 0.54 m

    I calculated the system's change in gravitational potential energy through the equation k=mgh. I used this equation twice, once for the 3.5 kg block with k =(3.5)(9.8)(-0.54) and once for the 1.0kg block, k = (9.8)(1.0). I got -18.522J & 5.292. Is the change just -18.522 - 5.292 J...
  39. V

    Determining Inertia of a block

    Since the problem gave me the kinetic energy and inertia of the iron block, I could plug it into the equation K = 1/2 mv^2 to get the final velocity, I got sqrt(30) for the block's final velocity. From there, I don't really know where to go, I could plug it into the equation above, but ΔE int is...
  40. R

    Collision between a block and a curved up-ramp surface

    I tried to solve this question using conservation of momentum. The momentum of the system is mc(vc)=mcvc'+mbvf'. But after that I have no idea I want to use the conservation of kinetic energy but the question doesn't say it's elastic collision, I need to find the velocity of the mb after the...
  41. Yalanhar

    Acceleration of a moving wedge with a falling block

    When the box travels a ## X## distance, the wedge travels ## \frac{X}{2}##. So ##a = 2A## Using the wedge as a non inertial frame: I didn't use (4). Using (2) on (3) and then on (1) I got: ##2mA=mgsin\alpha +mAcos\alpha + \frac{-mgcos\alpha sin\alpha +mAsin^2\alpha +MA}{2cos\beta -...
  42. Ammar2211

    A block of mass m is dropped onto the top of a vertical spring....

    Summary:: A block of mass m is dropped onto the top of a vertical spring whose force constant is k. If the block is released from a height h above the top of the spring, a) what is the maximum energy of the block? b) What is the maximum compression of the spring? c) At what compression is the...
  43. T

    Help with a problem about motion — bullet striking a block of wood

    I first plugged my given values into m1v1+m2v2=(m1+m2)vf. (0.002)(600)+(5)(0)=((0.0020)+(5))vf vf=0.24 m/s Next, I plugged my given values into F=ma. ((0.002)+(5))(9.8) F=49.02 N Next, I plugged my given values into Fdeltat=mdeltav. deltat=mdeltav/F ((0.002)+(5))(0.24)/(49.02)...
  44. A

    Engineering Transfer function to block diagram

    I am given the following two equations: and where E_1 is an output with corresponding input e and theta_o is an output with corresponding input E_3. The solutions that I was given are as follows: Unfortunately, I do not understand at all how to work out the block diagrams from the equations...
  45. C

    Why Doesn't Electron Shielding Block RF Radiation?

    I am watching this video; at the 8:20 mark it shows that a proton in a magnetic field will align with the magnetic field very easily if there is no shielding from electrons, and therefore will require energy to shift to the opposite spin state; makes sense to me. I also understand that when...
  46. L

    Oscillations of a Block Mass attached to a Spring on an Incline

    Why doesn't the incline angle play a role in changing the ##m## component of this equation? ##T = 2π\sqrt{\frac{m}{k}}## FOR QUESTION 25, PART B: ANSWER:
  47. PHYSICSSSTUDENT

    Conservation of energy in a bullet-wooden block impact system

    Suppose a bullet with high speed strike a wooden block and move together after collision. We know there is loss in total KE of bullet-wooden block system. The question is, if the part of the loss in KE of the bullet is transfer to heat energy, HOW to prove the CONSERVATION of ENERGY in this...
  48. Prabs3257

    Is Equating Energies a Better Solution for Finding Extension Under Spring Force?

    Its a very basic problem and my friend suggested a solution that we should equate mg and kx ie mg=kx and just plug in m=8 and x=0.16 but i think that we should equate the energies like mgx=1/2kx^2 ie because at the point where mg will be equal to kx the mass will still have a velocity hence it...
  49. DavidOB18

    How Can a Stationary Top Block Accelerate with the Bottom Block?

    I know the answer but don't understand the concept. The solution says the accelerations are the same but if the top block is at rest how can it be accelerating. I know you can view both blocks as the same system but can you not study them independently. Any help would be appreciated.
  50. spacestrudel

    How to find the max. compression of a spring given a block on an incline?

    Hello! I am stuck on part of a problem and was wondering what I am doing wrong. For part a of the problem, we were asked to find the impact speed. I did this in a photo below given the following values: Θ = 30 degrees. The initial velocity = 10 m/s. The coefficient of kinetic friction = 0.4...
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