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. J

    Block Universe Theory: Evidence For & Against

    Hi,guys,What is evidence against and for block universe theory?
  2. M

    Is the upward Ff of a stationary block on an incline more or less than mg?

    A block of mass m remains at rest on an incline. The force acting up the ramp on this block is a. 0 b. mg c. less than mg d. more than mg I understand that the force of friction cannot be more than the force of gravity because it would then move upward... but how is that the force of...
  3. Pythagorean

    Bill proposed to block public access to publicly funded research

    More threats to the open research community. Between this and SOPA... http://www.nytimes.com/2012/01/11/opinion/research-bought-then-paid-for.html?_r=1&scp=1&sq=research%20works&st=cse
  4. D

    Block Sliding, might use work energy theorum

    Homework Statement A block of mass 4.2 kg which has an initial velocity of 3.3 m/s at time t=0, slides on a horizontal surface. If a constant friction force of 10.2N is exerted on the block by the surface, what is the acceleration? Homework Equations Work Energy Theorum? .5 m vo2 -...
  5. C

    About acceleration of block with respect to wedge and ground

    Hi friendz I have a problem. If a block of mass m is placed over the wedge such that there is no friction then what is the acceleration of block 1with respect to wedge 2 with respect to ground Pleas reply. Thanks in advance. My sir said that it is different.Is it so.
  6. S

    MATLAB Creating a Block Tridiagonal Matrix in MATLAB

    Dear friends I have a problem in creating a block tridiagonal matrix. I try to create a block tridiagonal matrix in MATLAB and I tried everything but it is not working for me. I have matrices A, B, C of dimension 4*4. Elements od these matrices are dependent on (n) and in each n has different...
  7. B

    Release block on a moving inclined plane.

    Homework Statement A block of mass m is held motionless on a frictionless plane of mass M and angle of inclination θ. The plane rests on a frictionless horizontal surface. The block is released. What is the horizontal acceleration of the plane? (Introduction to Classical Mechanics by David...
  8. B

    Block Sliding Down Circular Ramp (w/ Friction)

    A block of mass m is positioned at the top of a quarter-circle ramp with radius R and friction coefficient μ. To find the velocity v at the bottom, I did the force summation equations in the n- and t-directions and came up with: n: N - mgsinθ = mv^2/R t: mgcosθ - μN = ma I then solve for...
  9. B

    A Case for the 4-D Space-Space Block Universe

  10. D

    How to block tunneling current?

    Dear forum members How to block tunneling current? Apart from barrier dimensions like height and thickness are there any other options? Say barrier geometry or chemical property, maybe some magnetic impurity to induce Kondo effect and scatter the tunneled electrons. Thank you in advance Dilema
  11. E

    Interpreting a signal block diagram to form transfer funciton

    Homework Statement Given the following block diagram. Calculate the transfer function H(z) and find \theta (f=\frac{f_{s}}{6}) Homework Equations H(z)=\frac{Y(z)}{X(z)} The Attempt at a Solution Ok So I know i need to find my y(k) output equation from this. I can then rearange the...
  12. W

    Block on Spring with Friction Problem

    Homework Statement A block of mass m is moving at a speed of v0 at a distance L away from a spring of on a table with coefficient of friction μk. How much does the block compress the spring? Determine the average power generated due to friction during the compression of the spring. I'm not...
  13. M

    Tension in a single rope holding a block, no motion.

    1. So this is a very basic question on tension, i assume, however every example provided in my book shows the tension within two cords. I can't seem to grasp the correct way to do this... Homework Statement A 2 kg block is suspended from a single rope. A horizontal force keeps the cord at...
  14. P

    Bullet in Block- 2D Projectiles w/ Motion

    Homework Statement A(n) 9 g bullet is fired into a 396 g block that is initially at rest at the edge of a frictionless table of height 0.9 m. The bullet remains in the block, and after impact the block lands 2.3 m from the bottom of the table. The acceleration of gravity is 9.8 m/s. Homework...
  15. J

    A 2.0 kg block is released from rest on a frictionless 30 degree incline.

    Homework Statement A 2.0 kg block is released from rest on a frictionless 30 degree incline. After sliding 0.80 m it comes in contact with the spring, and after sliding an additional 0.20 m, it comes momentarily to rest. What is the spring constant? I knew that spring constant is equal to...
  16. K

    Projectiles: Bullet Fired into Block

    Homework Statement A(n) 9 g bullet is fired into a 303 g block that is initially at rest at the edge of a frictionless table of height 1.9 m. The bullet remains in the block, and after impact the block lands 1.5 m from the bottom of the table. The acceleration of gravity is 9.8 m/s/s. Find...
  17. T

    Solving Max Displacement of Spring with 5kg Block and Friction

    Homework Statement block of mass m = 5 kg is connected to a spring having stiffness constant k = 49 N/m, as shown in the figure below. The surface between the block and the table has μk = 0.1 In this figure, the block is presently held in place with the spring stretched by x1 = 0.8 m...
  18. M

    Solving Bullet Impacts a Block: Force, Velocity & Distance

    Homework Statement A 50 g bullet at 50 m/s hits a block 2.0 m away. The coefficient of friction is 0.30. What is the force of bullet on the block, the velocity of the block and bullet and distance traveled by the block? Assume this is a perfectly inelastic collision. Known: m_b = .0050kg...
  19. nukeman

    Need quick help - Ball swings down, hits block - Speed of the block?

    Homework Statement Ok I can't seem to figure this out. Maybe I am tired, or strung out on coffee :), but I need some help! The image shows the question with diagram: Homework Equations The Attempt at a Solution Iv done this a few different ways, but all WRONG. The...
  20. F

    How to block off charge particles from an electron accelerator?

    Assuming an electron accelerator is firing electrons at a designated location to generate current. Is it possible to block it off before it reaches that location like with an iron shield or somesort. Is there a simpler or harder way to do this and is it possible to block it off completely? Thanks.
  21. Femme_physics

    Block Diagrams - Control Engineering. Basic Question

    (Go on easy on me, this is my first attempt and first course at control engineering) Homework Statement In systems who has a huge consumption of hot water, such as food factories, chemical industries or hospitals, it's customary to heat the water through fuel type "mazut". the hot water...
  22. S

    Block Time vs Q. Indeterminacy

    Block Time in relativity where past, present and future exist all the time seems to be in conflict with quantum indeterminism where the latter states the future is uncertain. So why do physicists still competely believe in Block Time? What is the consensus about this in the physics community at...
  23. S

    Acceleration of a Block at an Incline

    Homework Statement A rope applies a force T = 500N as shown as the 30kg block moves 14m along the incline. The length of the incline is unlimited. The coefficient of friction between the block and the plane is 0.33 What is the acceleration of the block? Homework Equations \SigmaF = ma...
  24. B

    Block Collides With Horizontal Spring

    Homework Statement A moving 2.40 kg block collides with a horizontal spring whose spring constant is 478 N/m. The block compresses the spring a maximum distance of 13.00 cm from its rest position. The coefficient of kinetic friction between the block and the horizontal surface is 0.360...
  25. J

    How Far Will the 3 kg Block Travel Up the Incline?

    Homework Statement A horizontal spring with a spring constant of 200.0 N/m is compressed 25.0 cm and used to launch a 3.00 kg block across a frictionless surface. After the block travels some distance, the block goes up a 32 degree incline that has a coefficient of friction of 0.25 between the...
  26. F

    Find Stress of the Rectangular Block

    For this question, I need to find the force that will be acting on a rectangular block. E = 193 x 10^3 MPa Max. Stress = 210 MPa F= 2000N The rectangular block is fixed at both ends (bolted on to another metal object) I need to find the dimensions for this block. L, length can be as...
  27. N

    Bullet & Block Homework: KE, Momentum & Energy Loss

    Homework Statement 40-g Bullet is fired with a velocity of magnitude v0=700 m/s into a 5kg block of wood. Coefficient of kinetic friction = 0.6. a) how far will the block move b) how long after impact does it come to rest c) percentage of energy lost on impact (block has no velocity...
  28. mrspeedybob

    A block of cheese hits a steel wall

    ...at greater then the speed of sound in cheese. The leading molecules of cheese cannot transmit the force of impact backward because the speed of force propagation is limited by the speed of sound in cheese so the molecules must move either sideways or into the steel. If the steel is strong...
  29. B

    Block On Incline Projected Up With Initial Speed

    Homework Statement A block with mass m = 7.4 kg slides down an inclined plane of slope angle 43.8 ° with a constant velocity. It is then projected up the same plane with an initial speed 3.10 m/s. How far up the incline will the block move before coming to rest? The attempt at a...
  30. B

    Block on an Incline with Varying Elevation

    Homework Statement Part one: A block is at rest on an inclined plane whose elevation can be varied. The coefficient of static friction is μs= 0.390, and the coefficient of kinetic friction is μk= 0.190. The angle of elevation θ is increased slowly from the horizontal. At what value of θ does...
  31. M

    Swinging Pendulum hits Block on Table- Find Distance and Acceleration?

    Homework Statement A 1.00 kg pendulum hanging from a length 1.50 m starts horizontal to the ceiling and swings (until it's perpendicular to the ceiling) to hit a 4.00 kg block. The coefficient of friction is .30. a) What distance does the block travel? b) Assuming there is no friction...
  32. M

    PE/KE-Bullet Hits a Hanging Block?

    PE/KE--Bullet Hits a Hanging Block? Homework Statement A .05 kg bullet hits a 4 kg block hanging 1.5 m from the ceiling, displacing it by a height of .50 m. What is the KE of the bullet before it hits the block, and what is the max PE of the block? (So basically, a bullet hits a hanging...
  33. D

    Bullet passing through block of wood. Find max height of the wood.

    Homework Statement A bullet of mass 0.005kg is shot at a suspended block of wood with mass 1kg. The bullet initially has a speed of 200m/s, and passes through the block of wood. The bullet passes through the wood, and 50J of work is done deforming the shape of the bullet and block. If the...
  34. B

    An ideal gas, and a block of copper, have equal volume of 0.5m^3

    Homework Statement An ideal gas, and a block of copper, have equal volume of 0.5m^3 at 300K and atmospheric pressure. The pressure on both is increased reversibly and isothermally to 5atm. Find the work done of each if the compressibility of copper is 0.7X10^-6 atm-1 the atmospheric...
  35. A

    Block released on frictionless ramp hits spring

    Hi, folks. Studying for an upcoming Physics exam. I've got a few example problems which the professor has solved—and am getting a different answer, but I don't know where the fault is in my reasoning. Could someone tell me whether or not my answer is, too, correct? Homework Statement...
  36. L

    Block sliding down an incline then collides with another block question.

    Homework Statement In the diagram below, a block of mass M=17 kg slides down a frictionless inclined plane and collides elastically with another block of mass m=4 kg. If the mass at the top of the wedge is initially at a height of 6 m above the horizontal plane, what is the velocity of m after...
  37. F

    Block Tipping Over [Torque and Forces]

    Homework Statement A rectangular block 3m high and 1.8m wide weighing in at 7600N is pushed with a force 20.5° to the height of the block 1.6m from the bottom of the block. Calculate the Force Required to tip over this block. Homework Equations Torque = perpendicular force x...
  38. nukeman

    Small block on a track - Finding Normal forces and

    Small block on a track - Finding Normal forces and... Homework Statement Here is the question. Can someone please help, since I missed the section of class that went over this, any my textbook does not cover this well. Look below at question 1, a) and b) Homework Equations...
  39. T

    What would the temperature limit of heating metal block?

    I have this problem and it's something that's been annoying me all day that I just can't get my head around. Imagine a metal block, in direct thermal contact with a heating element and "the surroundings"; but the heater and "the surroundings" are not in direct thermal contact. (I'm supposing...
  40. E

    Force on Block A: 100N Left & Right?

    So this was a question that I had on a previous test and I'm looking for a definitive answer. The question is what horizontal force/s is/are acting on block A. I thought it was 100N to the left and 100N to the right, however some other students had argued it was only 100N to the right...
  41. E

    Can a block of aluminum become an electromagnet?

    So I have this huge solid cylinder of aluminum about a foot tall, and 2-3 inches in diameter. I understand that aluminum is not a permanent magnet. But it DOES conduct electricity. So, if I wrapped a conductor around it, and hooked that up to a power source, would the aluminum become an...
  42. C

    Block dropped onto vertical spring, finding work/speed/height

    I need some help with this problem, to check if my answers and formulas are right/how to solve the last parts... A 0.25kg block is dropped onto a vertical spring with spring constant k= 250 N/m. The block becomes attached to the spring and the spring compresses 0.12m before coming momentarily...
  43. A

    Find the center of mass of a block of wood in oil

    A small square plank of oak floats in a beaker half full of water. The piece of oak is 7 cm on a side and 3 cm thick and floats on its side as shown in Figure P10.80. Density of oak 750kg/m^3 Density of water 1000kg/m^3 There were two parts to the problem, the first is: Find the location of the...
  44. D

    Block Collision: Find Distance for Elastic & Inelastic Collisions

    Block 1 of mass m1 slides from rest along a frictionless ramp from height h = 3.1 m and then collides with stationary block 2, which has mass m2 = 5m1. After the collision, block 2 slides into a region where the coefficient of kinetic friction µk is 0.35 and comes to a stop in distance d within...
  45. K

    Simple block tension Newton gravity problem

    The 4.00kg block in the figure is attached to a vertical rod by means of two strings. when the system rotates about the axis of the rod, the strings are extended and the tension in the upper string is 80N. A: What is the tension in the lower cord? B: what is the speed of the block? FIGURE...
  46. E

    A block on a frictionless slope slides down and compresses a spring

    Homework Statement Hello, folks. I know this same problem has been answered before here but the previous responses are just not doing it for me, sorry! An inclined plane of angle θ = 20.0° has a spring of force constant k = 495 N/m fastened securely at the bottom so that the spring is...
  47. L

    Momentum of a Bullet Contacting a Block

    Homework Statement A bullet with a mass of 4.0 g and a speed of 650 m/s is fired at a block of wood with a mass of 0.095 kg. The block rests on a frictionless surface, and is thin enough that the bullet passes completely through it. Immediately after the bullet exits the block, the speed of...
  48. U

    Block sliding down an incline plane with a cord connected to a cylinder.

    Homework Statement A cord connected at one end to a block which can slide on an inclined plane has its other end wrapped around a cylinder resting in a depression at the top of the plane as shown in the figure. Determine the speed of the block after it has traveled 1.70 m along the plane...
  49. R

    What force is Block A exerting on Block B?

    Homework Statement This is a question that the teacher gives every week that we do in class. He gives the parameters without the actual numbers a week before so we can prepare. The teacher will give: - the masses for both blocks (different) - the coefficient of friction for both...
  50. U

    Displacement of wood block originally attached to spring

    Homework Statement A 180-g wood block is firmly attached to a light horizontal spring, Fig. 6-26. The block can slide along a table where the coefficient of friction is 0.30. A force of 20 N compresses the string 18 cm. If the spring is released from this position, how far beyond its...
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