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. G

    The rank of a block matrix as a function of the rank of its submatrice

    Hello everyone, I would like to post this problem here in this forum. Having the following block matrix: \begin{equation} M=\begin{bmatrix} S_1 &C\\ C^T &S_2\\ \end{bmatrix} \end{equation} I would like to find the function $f$ that holds rank(M)=f( rank(S1), rank(S2)). S_1 and S_2 are...
  2. G

    Square root of a squared block matrix

    Hi everybody, I’m trying to compute the square root of the following squared block matrix: \begin{equation} M=\begin{bmatrix} A &B\\ C &D\\ \end{bmatrix} \end{equation} (that is M^(1/2))as function of A,B,C, D which are all square matrices. Can you help me? I sincerely...
  3. D

    Calculating Horizontal Acceleration on 7.20 kg Block w/F1 & F2

    Two forces, F1 and F2, act on the m = 7.20 kg block shown in the figure below. The magnitudes of the forces are F1 = 56.8 N and F2 = 39.2 N. θ = 70.4°. What is the magnitude of the horizontal acceleration of the block? Relevant equations V0x=v0cosθ V0y=v0cosθ F=ma The attempt...
  4. N

    Insulated Copper Block Heated to 60 Celsius

    Homework Statement An insulated copper block receives energy at a rate of 100 W from an embedded resistor. If the block has a volume of 10-3m3 and an initial temperature of 20°C, how long would it take, in minutes, for the temperature to reach 60°C? Homework Equations Copper specific...
  5. S

    Obtaining inverses of block matrices

    Homework Statement Problem: Find and check the inverses (assuming they exist) of these three block matrices.: [1] {{I, 0},{C, I}} [2] {{A, 0}, {C, D}} [3] {{0, I}, {I, D}} Answer: [1] {{I, 0}, {-C, I}} [2] {{A^(-1), 0}, {-D^(-1) C A^(-1), D^(-1)}} [3] {{-D, I}, {I, 0}}...
  6. G

    Block of a covariance matrix

    Hello everybody, I’d like to present this math problem that I’ve trying to solve… This matter is important because the covariance matrix is widely use and this leads to new interpretations of the cross covariance matrices. Considering the following covariance block matrix ...
  7. lep11

    A block on the platform of an acceleratin truck

    Homework Statement A block is on the platform of an accelerating truck. The coefficient of static friction between the block and the platform is 0,25. What is the minimum time in which the truck can accelerate so that the block won't slide. During the acceleration the truck travels 75 meters...
  8. 1

    Estimating Cooling Time of Steel Block at High Temperatures

    I have a steel block (2.75m x 1.6m x 0.5m) sat at 1000°C in ambient air (22°C) How long will it take for a surface to drop to say 800°C should i use the heat transfer eq: Q=KA\DeltaT to find the power in joules per second, then transpose to find seconds somehow? Any help will be...
  9. S

    2009 F=MA # 24 (A block tipping down an incline)

    Homework Statement #24 https://aapt.org/physicsteam/2010/upload/2009_F-maSolutions.pdf Homework Equations T = rfsinθ The Attempt at a Solution FBD: Axes: (along the incline is x), perpendicular to that is y: Down: mgcosθ Up: N Right: mgsinθ Left: Ff (friction) If the box is...
  10. A

    What is the total force exerted by block 2 on block 3 ?

    Four blocks EACH of mass m = 10.0 kg are arranged as shown in the picture, on top of a frictionless table. A hand touching block 1 applies a force of Fh1 = 90.0 N to the right. The coefficient of friction between the blocks is sufficient to keep the blocks from moving with respect to each other...
  11. B

    Block on a Plane - Friction problem

    Block on a Plane -- Friction problem edit: deleted
  12. L

    Angle required to keep block from sliding down plane

    Homework Statement Here's a picture of the set up. I need to find out what angle I need to have the plane raised to so that the blocks aren't moving. Homework Equations F = ma The Attempt at a Solution For the first block F_k=μ_kF_N F_T+F_N-μ_kF_N+2mgcosθ+2mgsinθ=0 Since...
  13. F

    Heat sinking to Aluminum block and dissipation

    I am curious if someone can help be estimate heat sinking and dissipation in an Aluminum structure? What I am trying to do is is cool a hot liquid by just allowing it to heat the structure it is in since there is a reasonable amount of mass. Though the Aluminum structure is not designed...
  14. B

    I have got a lab on 'Braking distance of a wooden block'?

    Homework Statement I have got a lab on 'braking distance of a wooden block' and I have to find an equation which fits our experiment and find the uncertainty. I have an equation but I can't find the uncertainty. This is how, I went about my lab... To find the relationship between the mass...
  15. R

    Block on a slope, friction related

    A 300kg block is sitting on a slope of 20 degrees, the coeff of friction is 0.75, if the block is connected to a mass hanging vertically via a pulley, what is the mass of the hanging block such that it will overcome friction but not move the block F = mgsin20 for the force acting down the...
  16. S

    Help understanding a physics inertia experiment(Hammer and a heavy block)

    The experiment is the following: First part - The demonstrator puts an egg in the table, and places a heavy block resting above the egg, then he applies a force in the heavy block using the hammer, and the egg doesn't break. Second part - Now he takes the heavy block away, and instead...
  17. P

    Man running up a wheeled block.

    Hi, Homework Statement A man, whose mass is m, is running up a block of mass M (as shown in the diagram, please see attachment) with constant acceleration. The block is laid on a smooth ground. The man starts running from rest and the time it takes for him to traverse a distance L (across the...
  18. P

    Time for block of ice to reach 20 C in an isolating box.

    Hi, Homework Statement I am trying to find how long it will take 8 kg of ice whose temperature is -10 C, kept in a sealed isolating box placed in room temperature (25 C), to turn into water whose temp. is 20 C. The box is a cube whose side is 20 cm, the thickness of the box is 2 cm, and κ =...
  19. Z

    Spring connected to a block problem

    "Spring connected to a block" problem A block has an initial velocity of V and is connected to a damper and a spring like this: http://prism2.mem.drexel.edu/~rares/MassSpringDamper.jpg The problem is to figure how far the spring vill maximally be compressed. The damping is linearily...
  20. N

    Where does the energy go if I raise and lower a block?

    Okay, let's say I'm holding a wooden block. I then raise it above my head, then lower it to it's original position. Neither the kinetic or gravitational potential energy of the block has changed, so I have done no work on the block. However, I expended chemical energy to perform this action...
  21. T

    Rotational Dynamics Problem - Rod slipping against Block

    Homework Statement A uniform rod of mass m and length l is pivoted at point O. The rod is initially in vertical position and touching a block of mass M which is at rest on a horizontal surface. The rod is given a slight jerk and it starts rotating about point O. This causes the block to...
  22. I

    Exploring the Block Universe: The Current Physics Consensus on Block Time

    What is the current physics consensus of the block universe? I know its what Einsteins theory tells us and comes with relativity, Deutsch believes in a quantum many world block universe, but Rovelli and Dieks argue against block time? Is block time still the main accepted theory of time we...
  23. ghalimoglu

    How can i block the sound outdoor ?

    first of all sorry for my bad english. i know i need to improve it :) now, let's talk aobout my question. You know there is a few ways to block sound indoor with sponge or some materials. i searched on internet but i coulndt find anything to block sound outdoor. i have a project and i need...
  24. Z

    Projecting a block up to compress a spring

    Homework Statement A spring( k=200 n/m) is fixed at the top of a frictionless plane inclined at angle θ=40 degrees . A 1.0 kg block is projected up the plane from an initial position that is distance d=0.60m from the end of the relaxed spring with an initial kinetic energy of 16J. a) what is...
  25. N

    Mass-spring-damper subsystem inside a falling block

    Homework Statement A mass-spring-damper subsystem is falling inside a container m1. The system is confined to the vertical direction. Use Lagrange’s equations to find the EOM. A. Use x1 and x2 as generalized coordinates. B. The linear spring is unstretched when x2 – x1 = l...
  26. T

    Quick easy question block sliding down wedge

    Homework Statement If a block is let go from the top of a wedge elevated at a certain angle and slides down will it reach the bottom at the same time as if the wedge was moving and then we let the block slide? so neglect friction and air resistance and basically just let the block slide down...
  27. H

    Light ray passing thru plastic block

    Homework Statement A light ray passes downward into a block of transparent plastic with an angle of incidence of θ1 = 77.7°. If total internal reflection is to occur when the light strikes the left edge of the block at interface B, what is the index of refraction of the plastic? Homework...
  28. Z

    What Makes Iron Effective at Blocking Radiation Compared to Lead?

    Does anyone know how Iron compares to lead as a medium to block / absorb radiation? Do you know what wavelengths or spectrum iron is most effective against?
  29. J

    How many times will the block cross the rough patch

    A 7.50kg block slides down a frictionless ramp of height 2.25m at a velocity of 1.50 m/s. it crosses a rough patch that is 2.5m long and exerts a force of 3N. It then continues to the other side of the ramp which is angled at 35 degrees(I don't think this matters b/c it is frictionless). How can...
  30. P

    Finding Kinetic Energy and Velocity of a pulley / block system

    Homework Statement In the problem, a hanging block, m, is attached to a pulley that is mounted on a horizontal axle with negligible friction. The pulley has a mass of M=75kg and a radius of R=6.0cm. The mass of the hanging block is m=1kg. The block is released from rest at a height above the...
  31. A

    Mass of block given μK and Force?

    Homework Statement A student pushes a block with 240 N of force across a horizontal surface with a coefficient of kinetic friction of 0.4. The block accelerates at a rate of 0.88 m/s2. Find the mass of the block. Homework Equations μK = FK / FN F=ma The Attempt at a Solution...
  32. S

    Find Work done by block of gold?

    Homework Statement The density of solid gold at 20°C is ρ = 19.3 g/cm3. When it is liquid at 1064°C the density of the liquid state is decreased: 17.3 g/cm3. How much work does a block of gold of mass 407 kg do if it is heated at p = 1.0 atm from 20°C to 1064°C? Homework Equations...
  33. R

    Elastic Collision: ball held at angle released to hit a block attached to spring

    Homework Statement A 200 g rubber ball is tied to a 1.0 m long string and released from rest at angle θ. It swings down at the very bottom has a perfectly elastic collision with a 1.0 kg block. The block is resting on a frictionless surface and is connected to a horizontal 20 cm long spring of...
  34. N

    Inertia block on inclined surface problem? help with solution?

    A wheel of radius 0.20 m is mounted on a frictionless horizontal axis. A massless cord wrapped around the wheel is attaches to a 2.0 kg block that slides on a horizontal frictionless surface inclined at angle θ = 20 degrees with the horizontal. The box accelerates down the surface at 2.0...
  35. N

    Net torque question? Block 1 and block 2 hanging on pulley?

    In Fig. 10.45, block 1 has mass m1=460g, block 2 has mass m2=500g, and the pulley, which is mounted on a horizontal axle with negligible friction ahs radius R=5.0cm. When released from rest, block 2 falls 75.0cm in 5.00 s without the cord slipping on the pulley. (e) What is its rotational...
  36. V

    Rolling ramp displacement due to weigh of block

    Homework Statement Basically there's a ramp; its inclined plane has length "a", the base has length "b" and its height has length "c". The ramp is stationary, but it has wheels under it. The ramp weighs 120N. The center of mass of the ramp is located at 2/3 of "b" on the horizontal axis...
  37. L

    Finding the energy lost in a collision as the bullet collides to the block

    Homework Statement a 50 g bullet hits and becomes embedded in a wooden block of as 450 g which is at rest on a surface (μ = 0.41) and is attached to a spring bumper. The block and bullet compress the spring bumper a distance of 20 cm. Is the spring constant is 250 N/m find initial speed of...
  38. L

    Two block collision (momentum)

    Homework Statement a)Two blocks are moving on a frictionless surface. The first block's mass is 1.07kg and its initial velocity is 5.98m/s. The second block's mass is 2.26kg and its initial velocity is 2.59m/s. What is the velocity of the 1.07kg block after the collision if the velocity of...
  39. L

    Spring, Block, KE, PE, Incline Problem: Why is KE=ZERO?

    Spring, Block, KE, PE, Incline Problem: Why is KE=ZERO?? A 250 g block is pressed against a spring of force constant 1500 N/m until the block compresses the spring 8.0 cm. The spring rests at the bottom of a ramp inclined at 60.0 degrees to the horizontal. Using energy considerations, determine...
  40. G

    Pressurized air in aluminum block help so it doesnt explode

    Pressurized air in aluminum block.. help so it doesn't explode! Hey everybody! Need some help with a design I'm comming up with for myself- it's an air valve block. What I'm having trouble with is figuring out how close I can make the holes to each other? I don't have any computing...
  41. P

    Work and energy of block of mass

    A block of mass 10kg is pulled along a straight horizontal road by a constant horizontal force of magnitude 70N in the direction of the road. The block moves in a straight line passing through two points A and B on the road, where AB = 50m. The block is modeled as a particle and the road is...
  42. A

    A bullet strikes a wooden block

    Homework Statement A 25 g bullet is fired at 150 m/s into a 2.0 kg block of wood hanging from a string 3.0 m long. The bullet becomes embedded in the block. To what height do the bullet and block swing? Homework Equations m1v1 = (m1+m2)vf 1/2 mv^2 = mgh The Attempt at a Solution...
  43. V

    What is the acceleration of the block on the incline?

    Homework Statement A mass m = 16.0 kg is pulled along a horizontal floor, with a coefficient of kinetic friction μk = 0.14, for a distance d = 8.3 m. Then the mass is continued to be pulled up a frictionless incline that makes an angle θ = 38.0° with the horizontal. The entire time the...
  44. U

    Force applied to block moving along table

    Homework Statement An object of mass is placed at rest at the point x=0 on a horizontal table and at time t=0, a horizontal force is applied to it given by Fx = c1t where c1 is a known positive constant. The coefficient of friction between the table and the object is u. If friction force...
  45. P

    Find the acceleration : block slides on a wedge

    sry for typo..it should be acceleration Homework Statement A block m slides down from a frictionless inclined surface (theta = 45) of a wedge, mass m, which is on a horizontal plane with coefficient of friction u. Prove that the wedge moves to the right with acceleration equal to...
  46. N

    Conservation of Energy, PE & KE, block on incline with KE & friction?

    A 4 kg bundle starts up a 30° incline with 128 J of kinetic energy. How far will it slide up the plane if the coefficient of friction is 0.30? So the solution to the problem is 128 = 4(9.8)(x)(sin30) + 0.30 (4)(9.8)(x)(cos30)...x = 4.29m I don't understand the solution. so 128 =...
  47. D

    Ricochet of moving / rotating block off a wall

    Thank you in advance for your help! The title pretty much says it all. I'm looking to write a 2D physics sim in which various objects can bounce off solid surfaces (without gravity). The objects are rotating and translating at a constant rate. We are dealing only with x and y - not z...
  48. S

    Mechanic about wood block, friction and pulley

    Homework Statement Two objects A and B weighing 50 N and 80 N respectively were connected by a light string over a fixed pulley. A was put on a reasonably long and horizontal table surface. The coefficient of sliding friction between A and the table surface is μ = 0.3 while the friction...
  49. M

    A 4.4kg block is pushed along the ceiling

    Homework Statement A 4.40 kg block is pushed along the ceiling with an constant applied force of F = 84.0 N that acts at an angle θ = 50° with the horizontal. The block accelerates to the right at 6.92 m/s2. Determine the coefficient of kinetic friction between the block and the ceiling...
  50. L

    Status of the block universe in the field of physics

    Hi. I did a quick search for threads on the block universe and came across one about the implications of the block universe. That was closed though because it was too philosophical. I don't really want to know about the implications of the block universe, I'm just wondering how physicsts...
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