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. S

    Block on Spring SHM, Finding angular frequency

    Homework Statement An "ideal" spring with spring constant 0.45 N/m is attached to a block with mass 0.9 kg on one end and a vertical wall on the other. The floor has negligible friction, and you give the block a push and then let go. You observe that the block undergoes simple harmonic motion...
  2. T

    Force of a block on an incline above a horizontal

    Homework Statement The block shown in figure #1 above has a mass of 4.30 kg. The applied force F has a magnitude of 31.2 N and is directed at 38.0˚ above the horizontal frictionless surface the block in on. What is the magnitude of the normal force that acts on the block? Homework Equations...
  3. Adgorn

    Proof regarding determinant of block matrices

    Homework Statement Let A,B,C,D be commuting n-square matrices. Consider the 2n-square block matrix ##M= \begin{bmatrix} A & B \\ C & D \\ \end{bmatrix}##. Prove that ##\left | M \right |=\left | A \right |\left | D \right |-\left | B \right |\left | C \right |##. Show that the result may not be...
  4. javii

    Determine the initial acceleration of the 15-kg block

    Homework Statement Determine the initial acceleration of the 15-kg block if (a) T = 23 N and (b) T = 26N. The system is initially at rest with no slack in the cable, and the mass and friction of the pulleys are negligible. I have attached a picture of the problem. The Attempt at a Solution a)...
  5. EthanVandals

    How long does it take to push this block at an angle?

    Homework Statement A 100 kg block is pushed across a level frictionless surface at a 60 degree angle, with a force of 20 Newtons. How many seconds does it take to go 100 meters? m = 100kg Mu = 0Homework Equations F = MA The Attempt at a Solution I sketched out the problem on my paper here...
  6. I

    Newton's 2nd Law Problem, Angle exerted on block by surface

    Homework Statement Problem: A 12.0-kg block is pushed to the left across a rough horizontal surface by a force that is angled 30.0◦ below the horizontal. The magnitude of the force is 75.0 N and the acceleration of the block as it is pushed is 3.20 m/s^2 . What angle does the force exerted on...
  7. anony123

    Why does adding more pulleys increase the force on a block?

    Hello, First of all, I'm new to this forum and to not know whether this thread is in the right place or not. If not, feel free to replace it. I'm in my first year of university, studying industrial engineering. On a test I got the following image: The red square is a block with a specific...
  8. D

    How Does Friction Affect the Acceleration and Tension in a Two-Block System?

    Homework Statement A block of mass m = 0.500 kg rests on top of a block of mass M = 2.50 kg which is on the floor. A string attached to the block of mass M is pulled so that its tension is T = 7.00 N at a 25.0o angle to the horizontal as shown. The blocks move together across the horizontal...
  9. S

    Double slit problem with glass block

    Homework Statement Light of wavelength 600 nm passes through two slits separated by 0.20 mm and is observed on a screen 1.0 m behind the slits. The location of the central maximum is marked on the screen and labeled y=0. (I only need help on the last 2 parts, but I will list all of them in...
  10. J

    Find y(t) for, x(t) = sin t and TF of a block is 1/(s+1)

    Homework Statement Find y(t) for, x(t) = sin t and TF of a block is 1/(s+1) Homework Equations Using Laplace of Input and then multiply laplace with TF to get O/P laplace and then doing Laplace Inverse The Attempt at a Solution Images are pasted below. Typed solution: Transfer Function...
  11. A

    Block with "incline Force" - 3

    Homework Statement A block of mass m1 (8.5 kg) lies on a flat (non-incline) plane, with friction coefficient μ (0.2). It is pulled by a force F (32 N) that has makes an angle α (22°) with the plane. Determine: - Acceleration - After how much time t the body will have a velocity v = 1.2 m/s2...
  12. oobgular

    Fluid Mechanics Question -- fluid on block?

    Homework Statement A block has dimensions 0.015 x 0.2 x 0.1 meters and weighs 6 Newtons. A 15mm-diameter jet of water is deflected by the block. Find the flow rate needed to tip the block. Homework Equations Mass conservation: ∂/∂t ∫(control volume)ρ d∀ + ∫(control surface) ρv•n dA = 0...
  13. M

    A block diagram reduction [sign error]

    I try to solve a block diagram reduction example but when I did the operations, sign of one operation is incorrect. I tried to understand why it is so? Would somebody like to help me. (1) First I carry the feedback into the parallel line. (2) I add +1/G1H1 in the parallel line because I...
  14. U

    Dynamics -- Velocity of a Block in a system of Pulleys

    Hey guys, I have been a long time lurker here but this problem has eluded me for a few hours now and my frustration at not being able to figure out what it is I am missing prompted me to finally pull the trigger on making an account here. I hope the way I wrote everything out is clear to...
  15. nothing909

    Pin configuration & Internal block diagram of an optocoupler

    Homework Statement In that pin configuration, what does the triangle and rectangle in the middle represent?
  16. Shardul Khare

    B Exploring the Physics of Stacked Blocks: No Normal Force on Block A

    If 3 blocks have some mass(a,b,c) are kept on one another (Vertically i mean)...Why block a doesn't experience the normal force exerted by the ground on block c? won't that force get transferred through b to a?
  17. M

    Can I Simplify a Block Diagram by Making Multiple G5 Blocks?

    I would like to ask why cannot I think G5 in series with G3(G4+G6G7) and then after muliplying them why I cannot think of G5*G3(G4+G6G7) in parallel to G2 so sum G2 and G5*G3(G4+G6G7) ? Thank you.
  18. N

    Find coefficient of kinetic friction of block and ramp.

    Homework Statement A small block is on the point of slipping down a rough ramp inclined at 35 degrees to the horizontal. a) What is the coefficient of static friction between the block and the ramp? Answer μ_s = 0.70 b) The ramp is attached to the edge of a 0.8 m high table. After the block is...
  19. J

    MCAT Collisions of a wooden block and bullet

    Hi guys, I'm currently going over Berkerley Review Physics example problem and got confused on a question: Ex. 4.1a : A sharpshooter fires a gun at a wooden block of mass M. If the bullet, of mass (m), becomes lodged inside the block, then which of the following is NOT true? The answer was...
  20. R

    Calculating Distance Traveled by Cart with Sliding Block

    Homework Statement A block of mass m =0.75 kg is set on a large cart of mass M = 6.5 kg. The cart's rollers are frictionless, but there is a coefficient of kinetic friction of 0.36 between the cart's surface and the block. The cart is at rest when the block is given an initial speed of 5.2...
  21. M

    A spring with a force constant

    Homework Statement Homework Equations These are the equations he provided. The Attempt at a Solution I actually have no idea how to do them. So any help would be much appreciated.
  22. S

    Height block reaches on accelerating quarter pipe

    Homework Statement A block in the shape of a quarter circle moves at constant acceleration across the floor. At some moment a small block of mass m, which is at rest with respect to the floor, is placed atop the horizontal part of the large block. There is no friction in this problem. Assuming...
  23. N

    Find the height the block rises to after an elastic collision

    Homework Statement Two blocks are free to slide along a frictionless wooden track ABC as shown below. The block of mass m1 = 5.09 kg is released from A. Protruding from its front end is the north pole of a strong magnet, repelling the north pole of an identical magnet embedded in the back end...
  24. UsableThought

    Retired writer & physics fan, hope to overcome math block

    Hi - I'm a writer/editor/writing coach/teacher, now retired - alas, more due to disability rather than age. My speciality when I was working was various sorts of non-fiction. I particularly enjoyed coaching professionals writing their first books, on various topics in business, the non-profit...
  25. KentVibEngineer

    Pulley rotational speed in block and tackle

    Homework Statement For the pictured block and tackle system, formulate an equation to solve for the rotational speed of each sheave wheel for a given line pull speed. (ignore friction, slippage, line stretch) (Mass, force, efficiency, mechanical advantage are not the focus of this. Pulley...
  26. H

    What is the force imparted by the bullet on the block

    Homework Statement A bullet with a mass of 0.045 kg is shot at 560m/s fwd, and it gets dislodged in a stationary block that is 0.5kg. The collision lasts 0.35 seconds. What is the force imparted by the bullet on the block? Homework Equations F=(m(vf-vi))/t The Attempt at a Solution...
  27. Cocoleia

    Hamilton equation for a block on an inclined plane

    Homework Statement I am asked to find the Hamilton equations for a block on an inclined plane (no friction) Homework EquationsThe Attempt at a Solution Please ignore the fact that my steps are written in French (sorry!) I am no longer sure of what I'm doing when it comes to finding the...
  28. S

    Can a Box Block UVC Light for Bacteria-Killing Experiment?

    Hello, I am doing an experiment where I am using a UVC light (254 nm) to kill bacteria for a science fair project. Will putting the light bulb in a card board box be enough to make sure no light escapes? Should I use a reflective material on the inside of a box, like a foil? Thanks!
  29. Vanessa Avila

    Finding time of how long the block travels (SHM)

    Homework Statement A small block is attached to an ideal spring and is moving in SHM on a horizontal, frictionless surface. When the amplitude of the motion is 0.090 m , it takes the block 2.52 sto travel from x= 0.090 m to x= -0.090 m . If the amplitude is doubled, to 0.180 m , how long does...
  30. I

    How can I reduce a controller with block reduction and find a transfer function?

    < Mentor Note -- thread moved to HH from the technical forums, so no HH Template is shown > Hi! I've been working on reducing a controller with block reduction in order to understand it and I have trouble to continue since I've stumbled across something that I haven't seen before. My goal is...
  31. A

    What is the acceleration of the block?

    Homework Statement A 50.0-kg block is being pulled up a 16.0° slope by a force of 250 N that is parallel to the slope. The coefficient of kinetic friction between the block and the slope is 0.200. What is the acceleration of the block? Homework Equations Fk=μkN F=MA The Attempt at a...
  32. I

    PID control and block reduction

    < Mentor Note -- thread moved to HH from the technical forums, so no HH Template is shown > Hi! I am trying to reduce a PID controller by using block reduction rules but I am having some trouble Here is the block: https://postimg.org/image/9am5n8bsp/ My attempt: 1. Multiply (1/I)*(1/s) ->...
  33. L

    Inelastic collision: block moving down a frictionless ramp

    Homework Statement In the figure provided, two suitcases are on a 6.36 m high ramp to passengers waiting in a baggage terminal. The top suitcase is released from rest, and it slides down the ramp and hits the second suitcase. If the suitcase at the top has a mass of 11.8 kg and the other...
  34. G

    What is a feed through term in block diagram?

    I`m reading some paper about control engeneering. But I don`t know what is feed through term exactly. Is it a connection between some point in one circuit?
  35. V

    Block slipping against two blocks

    Homework Statement In the setup , block C remains at rest and block A move towards left when system is released . If velocity of A is 'u' towards left at an instant , what is the vertical component of velocity with which B descends .What is the horizontal component of velocity of B at this...
  36. D

    Projected Block and Conveyor Belt

    Homework Statement It is a Matching Type Problem(a single entry in a column can be matched with more than one in the other column):- A block is projected with an initial velocity ##v_{\text{Block}}## on a long conveyor belt moving with velocity ##v_{\text{Belt}}##(at that instant) having...
  37. E

    Determine the speed of the block at the bottom of the inclin

    Homework Statement You release a block from the top of a long, slippery inclined plane of length l that makes an angle θwith the horizontal. The magnitude of the block's acceleration is gsin(θ) .Use the expression you derived in the previous part to determine the speed of the block at the...
  38. N

    Why a conductive shield doesn't block the magnetic field?

    Hi While studying the shielded wires, i noticed that the magnetic field of the inner conductor can penetrate the shield conductor (can be calculated in the region 3). However, the boundary condition of the magnetic field at the surface (between dielectric and perfect conductor) of a perfect...
  39. V

    Block on movable wedge pulley system

    Homework Statement What is the relationship between " acceleration of block with respect to wedge" and "acceleration of wedge " ? Homework EquationsThe Attempt at a Solution If the wedge moves by x units , then the string gets loosened/shortened at three places . The top two are x units...
  40. Vitani11

    What is the speed of block one when block 2 has fallen h?

    Homework Statement A block with a mass m1 is held in place on a table and is attached to a block with mass m2 by a massless inextensible string that passes over a massless pulley with frictionless bearings. The coefficient of static friction between block 1 and the table is μs and kinetic is...
  41. K

    Work and energy for a lowered block

    Homework Statement A cord is used to vertically lower an initially stationary block of mass M = 35 kg at a constant downward acceleration of g/5. When the block has fallen a distance d = 6.5 m, find the work done by the cord's force on the block. Find the work done by the weight of the block...
  42. RabbitWho

    Find the mass of a metal block with heat capacity 60JK

    Homework Statement A metal block of heat capacity 60 J K -1 loses 1MJ of heat energy to its surroundings. Find the decrease in its temperature. Homework Equations Q = m c Δ θ Heat energy added = mass x specific heat capacity x rise in temperature heat energy lost = blah blah blah x drop in...
  43. Cocoleia

    Time for a block to come to a stop on a horizontal surface

    Homework Statement I have a block of mass m on a horizontal surface, which is covered in oil. The tell me the viscous resistance force is a function of the velocity, F(v)=-cv1/2, where I am assuming c is a constant of some kind. I need to find the time that it will take for the block to stop...
  44. E

    A bullet pushing a knot out of a wood block

    Homework Statement You shoot a 0.0050-kg bullet into a 2.0-kg wooden block at rest on a horizontal surface (Figure 1) . After hitting dead center on a hard knot that runs through the block horizontally, the bullet pushes out the knot. It takes the bullet 1.0 ms to travel through the block, and...
  45. tensor0910

    Solve for friction coefficient of block on sp

    1. Homework Statement A block of mass 1.60 kg is connected to a spring of spring constant 152 N/m which is then set into oscillation on a surface with a small coefficient of kinetic friction. The mass is pulled back 34.6 cm to the right and released. On the first right to left oscillation...
  46. Cocoleia

    Block attached to a cord on an inclined plane

    Homework Statement I have a block of mass M attached to a cord of mass m on an inclined plane of angle θ . A force F is pulling the cord & block up the plane. I have to find the force exerted on the block by the cord. The surface is frictionless Homework Equations F = ma The Attempt at a...
  47. Cocoleia

    Block projected up inlcline with initial speed

    Homework Statement I have a block on an inclined plane (the angle is 40). The block is projected with an initial speed of 2m/s and μ=0.05. I need to find the time it takes the block to go up the inclined plane and return to the point it started out. Homework EquationsThe Attempt at a Solution...
  48. Amru123

    B Driving a nail into a wooden block

    We usually observe that in order to force a nail into a block we have to provide some support to the block.Can someone scientifically explain why we do it?
  49. thegreengineer

    Control theory: block diagram, problem (detailed below)

    I´m taking a course on control engineering and I have a test next Tuesday so I need to study the basics which are: Laplace transform, simplification of block diagrams, and analysis of transient and steady state responses. Right now I am dealing with the second one. I know the basic rules of...
  50. Mr Davis 97

    Solving a Simple Diff. Eq: Block in a Frictionless Ring

    Homework Statement This problem involves solving a simple differential equation. A block of mass ##m## slides on a frictionless table. It is constrained to move inside a ring of radius ##l## that is fixed to the table. At t = 0, the block is moving along the inside of the ring (in the...
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