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. cpscdave

    Python How Do You Include Header Files in Python?

    In c I quite often build header files with a bunch of predefined data. Fill it with structures or what not. Then to include that information in my program its a simple #include "myHeader.h" Is there a way I can do this in python? I've created another file "myHeader.py" Have put in some code to...
  2. G

    Control Systems Engineering - Block Reduction Help

    Homework Statement Hello, I'm trying to reduce the following block diagram Homework EquationsThe Attempt at a Solution I appear to be having some issues in doing this. The first thing that I did to reduce this block diagram was to take the forward path that has 2/(s+4) with negative...
  3. S

    Is the popular 4x4 winching strategy of a single block correct?

    Question – A single block reduces the force on the pull by ½ and double the length of the rope pulled and double the pulling force? This is the typical quote made on all popular 4x4 winching sites. I have found...
  4. gracy

    Max Velocity of Wedge: When Block Reaches Height h

    Homework Statement :There is a wedge of mass kept on smooth surface. M and block of mass m is sliding in the depression of the wedge.And there is wall in left of the wedge.At which instant velocity of the wedge will be maximum?(surface of contact between wedge and block is smooth) [/B]...
  5. Y

    Block slides across a sled on frictionless ice....

    Homework Statement Two students sit on opposite ends of a sled 6 m long initially at rest on frictionless ice. Each student has a mass of 50 kg; the sled’s mass is 40 kg. The student at one end slides a 2-kg object on the sled across to the other at a uniform speed of 5 m/s relative to the sled...
  6. gracy

    Wedge and block initial momentum

    Homework Statement :block slides on smooth triangular wedge kept on smooth floor.Find velocity of wedge when block reaches bottom. (image is attached) Homework Equations :Let the velocity of the triangular wedge be V.And v be the velocity of block m. [/B] applying conservation of linear...
  7. M

    Block and spring on a weird track (roller coaster)

    Homework Statement A block of mass m = 1.5 kg is launched from point A with speed VA = 12 m / s, in the circuit shown in Figure 4. If we assume that there is no friction determine: a) the speed of the block when it reaches the point C; Drawing of the problem: http://i.imgur.com/TrcMJ5I.png...
  8. personage

    Buoyant Force of a block in water

    A flask of water rests on a scale that reads100 N. Then, a small block of unknown material is held completely submerged in the water. The block does not touch any part of the flask, and the person holding the block will not tell you whether the block is being pulled up (keeping it from falling...
  9. M

    Spring on inclined plane with a Block

    Homework Statement A block of mass m = 4 kg, is held at rest on a spring (point A), spring constant k = 500 N / m, compressed by a distance AB = .DELTA.L as shown in Figure 3. When the block is freed , it reaches the point B ( non-deformed position of the spring ) with a velocity of VB = 5 m /...
  10. J

    Dynamics Problem: Incline Block and Moment of Interia

    Homework Statement Homework Equations ∑F=ma ∑M=Iα 3. The Attempt at a Solution I used the dynamic equilibrium formulas to find the tension. The tension helps me to find the acceleration of the block. Then, I used kinematics to find the velocity. But, I'm not getting the right answer.correct...
  11. Dan LaSota

    Vendor for Flint Glass Block or Prism

    Hi, I'm trying to put together materials to demonstrate the Faraday Effect. I need to locate the supplier of some flint glass (glass with lead oxide or similar materials increasing the Verdet constant), that I could use in my lab. I had found this from Mansion Schools...
  12. L

    Block on a vertical spring, finding frequency

    Homework Statement A block of mass m is on a platform of mass M, supported by a vertical, massless spring with spring constant k. When the system is at rest, how much is the spring compressed? When the spring is pushed an extra distance x, what is the frequency of vertical oscillation...
  13. G

    Finding the kinetic friction between the block and surface

    Homework Statement [/B] The block shown is pulled across the horizontal surface at a constant speed by the force shown. If M = 5.0 kg, F = 14 N and Theta= 35°, what is the coefficient of kinetic friction between the block and the horizontal surface? Homework Equations Fx = Fcos(theta) Ff = Fn...
  14. Dethrone

    MHB Determinant of Block Matrices: How Do Non-Zero Blocks Affect the Determinant?

    I don't quite follow this, can anyone explain?
  15. P

    Find Constraint Equation for Block on Wedge

    Suppose we want to find the constraint equation relating the acceleration of a block on a wedge to the acceleration of the wedge (see attached images). We can write: $$h - y = (x - X) \tan{\theta}$$ What if ##X## was measured to the centre of mass of the wedge for instance? Wouldn't the correct...
  16. tony873004

    What Is the Best Term for an Object Not Moving and Not Accelerating?

    A block is at rest on a ramp with an incline of 30 degrees above the horizontal. Find the force of static friction between the block and the ramp. One might be tempted to say that it equals the resultant force down the ramp: mg sin30. Or... A book is at rest on a table. What is the net...
  17. Qturtle

    Block diagonalization of a matrix

    Hi. i have a 4x4 matrix \begin{pmatrix} 0 & 1 & 1 & 1\\ 1 & 0 & i & -i\\ 1 & -i & 0 & i\\ 1 & i & -i & 0\\ \end{pmatrix} it has 2 eigenvalues and i want to block diagonalize it into a 2x2 block diagonal matrix. i can't seem to find the proper way to do that. do i need to have a commuting matrix...
  18. P

    Solve Block on Incline HW: F=ma & Fn=mgsinθ

    Homework Statement http://i.minus.com/iVbsy2FomprcM.PNG http://i.minus.com/iVbsy2FomprcM.PNG Homework Equations F=ma The Attempt at a Solution I'm struggling with the normal force and I'm not sure if the component of the force F is the cosine or sine. I see examples where its sine but that...
  19. P

    How Do Block Diagram Simplifications Reflect Underlying Equations?

    Homework Statement I am trying to understand the simplification between these two block diagrams Homework EquationsThe Attempt at a Solution I understand the 2s+1/s has been moved past the summing junction, resulting in the 2s. But I don't understand where the s/2s+1 block comes from
  20. Suraj M

    Solving Spring & Block Homework Problem

    Homework Statement The figure has 2 blocks, each 320 g connected by a light string. The horizontal surface is smooth. The block A is attached to a spring of spring constant 40 N/m whose other end is fixed 40cm above the horizontal. Initially the spring is vertical and unstretched. Homework...
  21. Suraj M

    Calculating the Height of a Block Launched from a Compressed Spring

    Homework Statement A block of mass 250 g is kept on a vertical spring with spring constant 100N/m fixed from below. The spring is now compressed to have a length 10 cm shorter than its natural length and is released. How high does the block rise?g = 10m/s Homework Equations E=½kx² and other...
  22. R

    Is there any mechanism for learning p block reactions?

    Do we have to rote memorize it or is there mechanism so that we can learn it easily? There are some ion exchange reactions which are simple like NaCl + H2O-------> NaOH+ HCl. but for example what about this? P4 + NaOH + H2O----> ?
  23. Poetria

    Solve Block Pulled Upward: Find Velocity in Terms of m, g, b

    Homework Statement An block of mass m is at rest on a horizontal surface. At t=0, a vertical upward force is applied to the block (for example, by pulling upwards on a string attached to the blcok). The magnitude of the vertical force depends on time as F=bt where b is a constant coefficient...
  24. AdityaDev

    How does the separation between block and spring affect the time period?

    Homework Statement a block of mass m as shown in figure lies on a smooth horizontal surface and springs are at natural length. when the block is displaced slightly then find the time period of oscillation Homework Equations $$T=2\pi\sqrt{\frac{m}{k}}$$ for series connection of...
  25. andyrk

    Plank with block of mass on top executing vertical SHM

    Homework Statement A plank on which a mass of mass m is put, is executing vertical SHM according to the equation y = sinωt + √3cosωt. At what time does the mass break of the plank and what is the value for the mass to break off ? Homework Equations The modified equation of motion looks like: y...
  26. T

    Transfer Function of Block Diagram

    Homework Statement The block diagram of a PM DC servo motor with current loop feedback is shown below: If Ki is adjusted such that J(Ki+R)2 >> 4KTKbL, show that the transfer function may be approximated by G(s) = (1/Kb) / (τms+1)(τes+1), where τm = J(R+Ki) / KTKb τe = L / (R+Ki)The...
  27. T

    What Force Does Block B Exert on Block A?

    Homework Statement A hand pushes on block A. Block B is on the right side of block A. If block a has A mass of 20kg and block B has a mass of 12 kg, and the acceleration equals 4m/s^s, what is the force that block B exerts on Block A [/B]Homework Equations F=m/a [/B]The Attempt at a Solution...
  28. C

    Plastic or glass that can block one colour/ wavelength?

    Hi, new member here, I know very little about physics so have no idea if this is a very basic question or not, but I was wondering if anyone knows the answer to the following: Does there exist a type of plastic or glass that (whilst remaining completely see through) can allow the user to see...
  29. 1

    Is the Frictional Force on a Sloped Block Greater Than Its Weight?

    Homework Statement A block is at rest on a rough incline . The frictional force acting on the block, along the incline, is A) greater than the weight of the block. B) equal to the weight of the block. C) zero. D) less than the weight of the block. Homework EquationsThe Attempt at a Solution...
  30. D

    Block slides down hemisphere; time to leave surface?

    A block is at rest at the top of a frictionless hemisphere of radius r. It is slightly disturbed at starts sliding down. I already know where it will leave the surface (height = 2r/3). My question is, WHEN will it leave the surface?
  31. B

    Is the tetrahedron the building block of the universe?

    I am new to physics, and my studies have taken me to this question. Mathetmatically, the tetrahedron is essentially the building block of geometries, does this make it then the building block of our universe? Though I understand this hasn't been proven and we haven't seen this, if mathematics is...
  32. L

    How Does Moving the Summation Block Affect the Equation in Control Systems?

    Hi there, I am struggling to understand how moving the summation (with H3) to before G1 will cause H3 to have to be divided by G1. I tried writing down how the equations would work to make sense of it but I still can't see how it works out. Please can someone explain this to me? Thanks, Laura...
  33. O

    Block on moving wedge (Maximum force for equilibrium problem

    Homework Statement Given: The friction between the block with mass 11kg and the wedge with mass 22kg is 0.48. The surface between the wedge with mass 22kg and the horizontal plane is smooth (without friction). The [A][/g] = 9.8m/[/2]. A Block is released on the incline plane (top side of...
  34. A

    Why Does the Force Calculation for the Block System Vary Between Solutions?

    Homework Statement What horizontal force must be applied to a large block of mass M shown in the figure below so that the tan blocks remain stationary relative to M? Assume all surfaces and the pulley are frictionless. Notice that the force exerted by the string accelerates m2. (Use the...
  35. T

    Angular momentum, block plus bullet

    Homework Statement A wooden block of mass M resting on a frictionless, horizontal surface is attached to a rigid rod of length l and of negligible mass. The rod is pivoted at the other end. A bullet of mass m traveling parallel to the horizontal surface and perpendicular to the rod with speed v...
  36. A

    MATLAB Could you check (if statment block) in my MATLAB code please?

    function RunlogisticOscilnumericalfisherfixedn0omega omega=1; N0=1; k = 10; A = 1; p0 = 0.1; tspan=(0:0.1:4); [t,p] = ode45(@logisticOscilnumerical,tspan,p0,[],omega,k,N0); figure(1) plot(t,p) xlabel('Time') ylabel('p') P = @(T) interp1(t,p,T); f = @(t) ( ( A.*( ( N0.*...
  37. CaptCoonoor

    Metallic coin over wooden block in glass of water - buoyancy

    Homework Statement So there is some water inside a container; the height of water inside the container is l. I placed a wooden block on the water and it's floating to some height x, on top of the block is a metallic coin (see the diagram below). What will happen if I throw that coin inside the...
  38. minimario

    Block Around a Track: Find Force & Coeff of Friction

    Homework Statement A small block of mass m = 0.50 kg is fired with an initial speed of v0 = 4.0 m/s along a horizontal section of frictionless track, as shown in the top portion of Figure P7.58. The block then moves along the frictionless, semicircular, vertical tracks of radius R = 1.5 m. (a)...
  39. R

    Finding the minimum force F which must be exerted

    Homework Statement Given: The friction between the block with mass 6 kg and the wedge with mass 18 kg is 0.27 . The surface between the wedge with mass 18 kg and the horizontal plane is smooth (without friction). The acceleration of gravity is 9.8 m/s^ 2. A block is released on the inclined...
  40. R

    Control systems block diagram reduction

    Homework Statement Hi I am having trouble simplifying the attached diagram with respect to the return summing blockHomework EquationsThe Attempt at a Solution there shouldn't be any superposition since there is only one input signal, in the attached file I've simplified A to Be: G3/(G2-G2G3G4)...
  41. W

    Velocity of a block attached to a pulley and cylinder

    Homework Statement A cylinder and pulley turn without friction about stationary horizontal axles that pass through their centres. A light rope is wrapped around the cylinder, passes over the pulley, and has a 3.00 kg box suspended from its free end. There is no slipping between the rope and the...
  42. N

    Friction Problem -- String, Block, Bucket & Washers

    Homework Statement A string is tied to a 4.4 kg block and 120g hanging bucket. Students add 20g washers one at a time to the bucket. The student are unaware that the[/B] coefficient of static friction for the block on the table is 0.42. A) what is the maximum force of static friction for the...
  43. N

    Friction Problem -- String is tied to a block and a hanging bucket

    USE OF THE PHYSICS FORUMS TEMPLATE IS REQUIRED ON ALL HOMEWORK PROBLEMS. PLEASE COMPLY WITH THIS IN THE FUTURE. A string is tied to a 4.4 kg block and 120g hanging bucket. Students add 20g washers one at a time to the bucket. The student are unaware that the coefficient of static friction for...
  44. C

    Question about mechanical energy and lowering a block

    When one lifts a block off of the ground and holds it in the air, the work done by one's lifting force is equal to the change in total mechanical energy of the block/earth system. Since the mechanical energy is KE+PE and since KE doesn't change during the motion, the work done by the lifting...
  45. Q

    Frequency of Oscillation of a Block & Spring

    Homework Statement An oscillator consists of a block attached to a spring (k=400 N/m). At some time t, the position, velocity, and accelleration of the block are x = 0.100m, v = -13.6 m/s, a - 123 m/s2 A) Calculate the frequency of the oscillation for the system B)What is the mass of the...
  46. E

    Block attached to spring on slope

    Homework Statement A block of mass M can slide freely (without friction) on a flat surface held at an angle \theta to the horizontal. The block is attached to a spring of natural length l and spring constant k. The other end of the spring is fixed to a nail driven into the sloping surface...
  47. P

    Block Sliding Down a Ramp that is Free to Slide

    Homework Statement A block with mass m rests on a smooth, frictionless ramp with mass M and height h. The ramp itself sits on a frictionless horizontal surface in which it is free to slide. The block slides smoothly down the ramp from rest. We want to find the speed of the block after it has...
  48. B

    Physics Graph question -- Pushing a block on a frictionless surface

    The diagram shows how a force along the x-axis varies with location. A block of mass 7.20 kg moves along the x-axis on a horizontal frictionless surface, influenced by this force. (Graph is attached) A) How much work is done by the force as the block moves from the origin to 8.0 m? B) If the...
  49. J

    Solving the Tension in a String Attached to a 10 kg Block

    Homework Statement A string is attached to a 10 kg block that lies on a horizontal surface. If the string is pulled horizontally with a force of 50 N, friction acting against it is 30 N. What is the tension in the string? Homework Equations F = ma The Attempt at a Solution Would it be 50 N...
  50. Satvik Pandey

    What Angle Causes a Block to Topple on an Inclined Plane?

    Homework Statement A block of base ##10cm \times 10cm## and height ##15cm## is kept on an incline plane. The coefficient of friction between them is ##\sqrt { 3 } ##. The inclination of the incline plain is ##\theta##. Find the value of theta for which the block begins to topple. Homework...
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