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. E

    Eigenvalue of overlapping block matrix

    I have got a problem in my research. For the following matrix, a a a a a a b b b b a a a a a a b b b b a a a a a a b b b b a a a a a a b b b b a a a a a a a a a a a a a a a a a a a a b b b b a a a a a a b b b b a a a a a a b b b b a a a a a a b b b b a a a a a a, does anyone know how...
  2. A

    Block moving around in a semi cricle

    Homework Statement A cylinder is cut out of a large block with mass M=4kg sitting on a table. A small block of negligible size and mass m=0.5kg is placed within the hole. All the surfaces are frictionless. The radius of the cut is R=0.80m and the angle is 25 degrees. Basically there's a...
  3. S

    Force required to tip block backwards

    Homework Statement There is a 2-D block with height H, width W, and mass M. (H > W) A force F is applied from behind the block at a height 0.1H from the ground. If the coefficient of friction is μ, what does the force F need to be to cause the block to tip backwards? Homework Equations...
  4. S

    Bullet Hits Block Attached to Spring What am I doing wrong?

    A wooden block of mass M = 1.83 kg is rest on a frictionless, horizontal table attached to the end of an unstretched spring (k = 217 N/m). A bullet of mass m = 8.02 g is fired horizontally into the block at speed vo = 394 m/s. The bullet comes to rest inside the block, and causes the mass to...
  5. K

    Block attached to spring is kicked,what distance will the spring stretch?

    A block, no friction, of 1 kg is attached to a spring rests on a horizontal surface with a length L. The spring is connected to a fixed point. The 1kg block is kicked and has a velocity of 1 m/s. As the block swings around the fixed point, the spring stretches to a total distance of L + x, at...
  6. L

    Help finding friction force of block moving across horizontal atwood's machine

    Basically we did a lab where you attach a pulley to the desk with a clamp and then have a friction block (three types: cork, plastic, and felt) attached to a string which is attached to a hanging mass. This basic setup is called an atwood's machine. The purpose of the lab was to identify the...
  7. P

    Ramp with block dealing with friction

    1. Consider a ramp of length L inclined at an angle Ɵ > (the angle of repose) to the horizontal. A block of mass m is placed at the high end and released from rest. (a) If µ = 0; what is the speed of the block at the bottom of the ramp? (b) Suppose now, that µ ≠ 0: What is the speed at some...
  8. S

    Density of Block Submerged into Swimming Pool

    A spring is mounted vertically at the bottom of an empty swimming pool. A block of mass M = 857 kg is attached to the spring, and it compresses the spring from its equilibrium position by distance xo. Now the swimming pool is filled with fresh water, and the block is submerged. You find the the...
  9. F

    Ramp, block, and elastic potential energy

    Homework Statement The spring in the figure below is initially compressed by 0.4 m in the position shown. If released from this position, block A travels 0.9 m before coming to a stop. The kinetic coefficient of friction is 0.8. What is the spring constant? (The spring is not fastened to...
  10. G

    How Far Does a Block Slide Up a Ramp Before Stopping?

    Homework Statement A block of mass 2.96 kg is sliding up a ramp with an initial speed of 12.8 m/s. The ramp is inclined from the horizontal at an angle of 36.4 degrees and the coefficient of kinetic friction is \mu=045. What is the displacement of the block along the ramp from the initial time...
  11. D

    Buoyant force of an aluminum block

    Homework Statement An aluminum block has a mass of 0.25kg and a density of 2700 kg/m cubic. a) calculate the volume of the aluminum block. b) Determine the buoyant force exerted on this block when it´s completely submerged in water of density 1000kg/m cubic. Homework Equations v = m/d The...
  12. B

    Analysing a pulley block system

    A pulley is mounted at the edge of a table. A block is connected to an identical block through the pulley(assumed to be weightless)by a weightless in-extensible thread of length 2l. The left block rests on the table at a distance l from the edge (where the pulley is mounted) while the right...
  13. G

    Period for SHM of a block on a spring shot by a bullet

    So I've been working on this problem for a while and can't seem to come up with anything and I don't really understand why I'm wrong in what I did. I could just get the answer online, but I actually want to understand what's happening. Homework Statement A rifle bullet with mass 8.12g and...
  14. F

    Automotive Small block Chev (classic) exhaust notes/tuning physics etc

    Somewhere in a dark corner of the "internet" lies a video of somebody that somehow crossed the leads from the header pipes so instead of all the primaries going into one collector some go into the other side collector...that produced a very exotic sound. Can someone tell me a little more...
  15. S

    Calculating impact force of a block accelerated by a spring

    I'm working on a small design project and need some help remember what equations to use here. Basically, we are creating a hammering device. A compression spring will be loaded, and a block on the end is accelerated into another block. I need to have it hit with a certain impact force so I am...
  16. H

    Block and tackle and tension forces

    Please, I need your help with this... it's starting to annoy me. I just don't know where are the tension forces... I get really confused doing this kind of things with pulleys and ropes. Look at pulley 4, I've seen that the tension force in the right is upward but why? Isn't that the...
  17. HelloCthulhu

    Node Analysis for LM2577 Block Diagram

    Greetings Members I'm a chemistry student doing some research [this is not homework!] on boost conversion and I need help discerning the node analysis for this step-up voltage regulator. I've found pretty decent tutorials on elements such as the comparator, npn transistor, and oscillator. But...
  18. B

    Visit With Paul Davies on Block Time

    Please forgive another round on the block universe, but I had a brief visit with Paul Davies and wanted to give the folks on the forum a report along with some quotes from his book. Sorry for the lengthy post. I was at a high school reunion in Phoenix last weekend and was staying with my...
  19. S

    Linear Momentum Block and Spring Problem

    Homework Statement A 0.500-kg block is attached to a horizontal spring that is at its equilibrium length, and whose force constant is 23.0 N/m. The block rests on a frictionless surface. A 5.60×10^-2 kg wad of putty is thrown horizontally at the block, hitting it with a speed of 2.00 m/s...
  20. E

    I=mv^2/w^2-2mgh/w^2Find Inertia of Wheel for Block & Pulley Homework

    Homework Statement A block of mass m=2.4kg is attached to a string that is wrapped around the circumference of a wheel of radius r=7.6cm. The wheel rotates freely about it's axis and the string wraps around it's circumfrence without slipping. Initially, the wheel rotates with an angular...
  21. phosgene

    Block moving on a frictionless loop

    Homework Statement A block moves on the frictionless slide shown in the diagram. What is the minimum height from which the block can be released if it is to complete the loop without leaving the surface of the slide? (Assume that the dimensions of the block are small compared to R, and that...
  22. Y

    Does copper or aluminum sheet block magnetic signal?

    I have a discussion about shielding of noise generated by appliance and florescent lights. I know both Al and Cu are not magnetic material. BUT all noise are time varying meaning it is EM field. Good conductor block E field as loss is very high. How does that work when only the B field can pass...
  23. G

    Calculating Acceleration of a System with Two Crates on a Horizontal Surface

    I have a question on block that I was solving in my book. I got the answer right but different procedures for doing it I want to make sure my logic is correct,and I didn't get the answer out of probability. Two crates of mass 75kg and 110kg, are in contact and at rest on a horizontal...
  24. B

    Bullets, block, and conservation of linear momentum

    Hello, I've been stuck on this problem and would really appreciate if someone could help me: A block of mass MB = 4.75 kg is initially at rest on a level rough surface for which the coefficient of kinetic friction is given by uk = 0.455 . Two bullets of equal mass Mb = 0.023 kg are moving...
  25. E

    How far does the putty-block system compress the spring?

    Homework Statement a .46kg block is attached to a horizontal spring that is at equilibrium length, and whose force constant is 22 N/m. The block rests on a frictionless surface. A 5.2x10-2 wad of putty is thrown horizontally at the block, hitting it with a speed of 2 m/s and sticking. How...
  26. E

    Does an Inelastic Collision Affect Conservation of Mechanical Energy?

    Homework Statement a .440 kg block of wood hangs from he ceiling by a string, and a 7.3x10^-2 kg wad of putty is thrown straight upward, striking the bottom of the block with a speed of 5.50 m/s. The wad of putty sticks to the block. is the mechanical energy of this system conserved? how...
  27. P

    Block Movement Dynamics: Solving for Time, Acceleration, and Distance

    Homework Statement Hi guys. First of all, great forum you've got here. I have a problem and I hope you can help me with this one. Block of mass m lies on a rough horizontal surface. In the period 0 - t1, the block is moving due to the force F(t), which varies depending on the time. In...
  28. S

    Concervation of Momentum: Bullet and Block of Mass

    A bullet of mass m = 19.7 g traveling horizontally at speed vo = 445 m/s strikes a block of mass M = 854 g sitting on a frictionless, horizontal table. The bullet comes out the other side of the block at speed v = 415 m/s. What is the speed of the block after the bullet exits the block? Using...
  29. M

    A bullet strikes a block like boom boom pow

    Homework Statement A small wooden block with mass 0.750 kg is suspended from the lower end of a light cord that is 1.48m long. The block is initially at rest. A bullet with mass 0.0118kg is fired at the block with a horizontal velocity V0. The bullet strikes the block and becomes embedded...
  30. M

    What is the direction of acceleration for the block moving on the xy plane?

    Homework Statement A small block with mass 0.0400 is moving in the xy-plane. The net force on the block is described by the potential- energy function (5.80 )-(3.50 ). Homework Equations inverse tangent of Fy/Fx = angle of acceleration The Attempt at a Solution The question...
  31. B

    Block moving down circle, a straight path, then into a spring

    Homework Statement Consider the track shown in the figure. The section AB is one quadrant of a circle of radius 2.0 and is frictionless. B to C is a horizontal span 3.5 long with a coefficient of kinetic friction = 0.27. The section CD under the spring is frictionless. A block of mass 1.0...
  32. C

    A block is pulled with constant tension up an incline, find the distance?

    Homework Statement A mass m = 13kg is pulled along a horizontal floor with no friction for a distance of d = 5.1m. Then the mass is pulled up an incline that makes an angle theta = 39 degrees with the horizontal and has a coefficient of kinetic friction u = 0.39. The entire time the...
  33. Chestermiller

    Does the Block Universe Theory Affect Our Understanding of Time and Reality?

    I’m relatively new to Physics Forums, so please go easy on me guys. I’m trying to get an understanding of the so-called Block Universe concept and its implications, but I need help. I’m going to start out by articulating my current understanding, and then try to apply this understanding to...
  34. J

    What fraction of the distance do the block move?

    A block slides a distance d down a frictionless plane and then comes to a stop after sliding a distance s across a rough horizontal plane, as shown in the accompanying figure. What fraction of the distance s does the block slide before its speed is reduced to one-third of the maximum speed it...
  35. J

    A Block Sliding Across the Floor

    Homework Statement A box slides across a frictionless floor with an initial speed v = 3.2 m/s. It encounters a rough region where the coefficient of friction is µk = 0.1. If instead the strip is only 1.56734693877551 m long, with what speed does the box leave the strip? Homework Equations...
  36. S

    Galvanization and more reactive block

    When I galvanize iron or attract a more reactive block of metal to iron, that metal will oxidise instead of the iron. I understand that anions need to be present for the reaction to occur as the more reactive metal will have transferred its electrons to iron. So the eg magnesium will oxidise to...
  37. E

    Calculating Motion of a Mass Attached to a Spring on an Inclined Plane

    A spring (75 N/m) has an equilibrium length of 1.00 m. The spring is compressed to a length of 0.50 m and a mass of 2.2 kg is placed at its free end on a frictionless slope which makes an angle of 41 degrees with respect to the horizontal. The spring is then released. a) If the mass is...
  38. P

    Block on inclined plane with pulleys and friction

    Homework Statement coefficient of kinetic friction = 0.15 Find the acceleration of block a. Homework Equations see below The Attempt at a Solution http://www.wolframalpha.com/input/?i=-200sin30%2B0.15*200cos30%2B2x%3D-200%2F32.2*a%3Bx-40%3D40%2F32.2*b%3Ba%3D0.5*b I used x for...
  39. F

    How to Solve for Two Variables in Mathcad?

    I'm having trouble solving for two variables in Mathcad. I'm relatively inexperienced with this software and I'm not sure whether it's the software or my math but anyway I've included screen dumps to highlight the problem. I have tried the Given/Find block in two different ways. The first does...
  40. G

    Work of kinetic friction on block in vertical circle

    Homework Statement 1. Homework Statement A block of mass 0.015kg enters the bottom of a circular, vertical track with a radius R = 0.3m at an initial velocity of 4/ms. If the block loses contact with the track at an angle of 130 degrees, what is Wk, the work done by kinetic friction...
  41. G

    Block in a verticle circle with friction

    Homework Statement A block of mass 15g enters the bottom of a circular, vertical track with a radius R = 0.5m at an initial velocity of 4/ms. If the block loses contact with the track at an angle of  = 130, what is Wk, the work done by kinetic friction...
  42. C

    Work done by pulling block over surface.

    Homework Statement A 80-kg block is pulled across a rough surface a distance of 1.25 metres. How much work was done in moving it? The coefficient of static friction was 0.3 and kinetic friction was 0.2. Assume the velocities were very low. Homework Equations W = fd ?? The Attempt at...
  43. T

    Acceleration of a car pulled by a block falling (pulley)

    Homework Statement A car and pulley system are setup as shown. Find the acceleration of the car. The car wheels have a friction coefficient of 0.15. The car has a mass of 0.05 kg while the block has a mass of 0.02 kg. http://sadpanda.us/images/836771-GBD7SB9.jpg *sorry if the picture is bad I...
  44. S

    How can I use Gauss elimination to zero out the elements of a block system?

    1. See the following picture: http://imageshack.us/photo/my-images/715/math5610.jpg/ Essentially what I'm trying to do is solve a linear block system. I have got to the point where I now need to "add multiples of the top rows to clear out C." Now, I'm sure this is the easy part as I've...
  45. J

    An Experiment Consists of Pulling a Heavy Wooden Block Across a Level Surface

    Homework Statement An experiment consists of pulling a heavy wooden block across a level surface with a spring force meter. The constant force for each try is recorded, as is the acceleration of the block. The data are shown below: Force F in Newtons: 3.05 | 3.45 | 4.05 | 4.45 | 5.05...
  46. P

    Distance a Block Moves up a Ramp

    A mass m is moving at a speed of Vo and slides smoothly onto a sloped big block of mass M. The big block can also move on the table surface. Assume that everything moves without friction. After the small block reaches the height h on the slope It slides down. Find the height h. Problem Number...
  47. Femme_physics

    Did I get my block diagrams right?

    In the drawing is described a system to the control flow of a liquid. The control is done by changing the rotary speed of the electrical engine that moves the pump. Changing of the speed is done by changing the voltage for the motor.BUILD A BLOCK...
  48. I

    What is the various function block in a grid tie VAWT system?

    Homework Statement Hi, i don't know really am i suppose to ask here but I've still try! I'm actually required to do a report on grid-tie VAWT system which i have taken some pictures (attached file below) on the installation site. But I'm quite puzzled with the picture pertaining the "Router...
  49. M

    How to Simplify a Block Diagram to Obtain Y/R?

    I am having trouble trying to obtain Y/R from the block diagram below: the only thing i understand so far is that the bottom right loop is a feedback loop and can be simplified to 1/(s+a1). i know b1s can be obtained from the right loop, but i am having trouble getting to that point. i know it...
  50. H

    Fluid mechanics,wooden block in water and oil

    Homework Statement A cubical block of wood, 10 cm on a side, is placed in a glass cup whose higher end is open to the atmosphere. The wood is in equilibrium at the interface between water and oil with wood’s lower surface 2 cm below the interface. The density of oil is 790 kg/m3. a) What is the...
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