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. J

    Displacement of spring of a block going down an incline

    Homework Statement An inclined plane of angle θ = 20.0° has a spring of force constant k = 455 N/m fastened securely at the bottom so that the spring is parallel to the surface as shown in the figure below. A block of mass m = 2.71 kg is placed on the plane at a distance d = 0.330 m from the...
  2. A

    Block Pushed Up a Vertical Wall

    Homework Statement What force is needed to move a 10 pound block up a vertical wall at a constant speed by pushing at an angle of 53 degrees with the vertical? Mu=0.3 At what minimum angle with the vertical would you be unable to push the block at all regardless of how large the force...
  3. K

    Bullet into block of wood on table edge

    Homework Statement A 17 g bullet traveling 475 m/s strikes a 0.7 block of wood that is balanced on a table edge 0.7 m above ground. If the bullet buries itself in the block, find hte distance D at which the block hits the floor. Diagram: Homework Equations Wnc = delta KE + delta PE...
  4. T

    Find Frictional force on a block

    Homework Statement A block of mass 9 kg rests on a plane inclined at an angle of 30◦ . The static coefficient of friction between the block and the plane is 0.7. What is the frictional force on the block? 1. 9.36841 N 2. 76.3834 N 3. 53.4684 N 4. 44.1 N 5. 30.87 It is not # 3. I...
  5. K

    Work on Block in Vertical Circle: MasteringPhysics

    Homework Statement A small block with mass 0.0325 kg slides in a vertical circle of radius 0.475 m on the inside of a circular track. During one of the revolutions of the block, when the block is at the bottom of its path, point A, the magnitude of the normal force exerted on the block by...
  6. T

    Find Frictional force on a block

    Homework Statement A block of mass 9 kg rests on a plane inclined at an angle of 30◦. The static coefficient of friction between the block and the plane is 0.7. What is the frictional force on the block? 1. 9.36841 N 2. 76.3834 N 3. 53.4684 N 4. 44.1 N 5. 30.87 Homework...
  7. P

    Friction: what is the net force on the block the instant that it starts to slide

    Homework Statement The coefficient of static friction between a block and a horizontal floor is 0.40, while the coefficient of kinetic friction is 0.15. The mass of the block is 5.0 kg. If a horizontal force is slowly increased until it is barely enough to make the block start moving, what is...
  8. A

    Forces: Wedge and Block Problem + Pulley System Problem

    Homework Statement 9) A 15 kg wedge is pushed along a frictionless surface. There is no friction between the wedge and the block. What force, F, is required to keep the block from sliding up or down the wedge? See attachment for diagram. 10) Find the tension, T. See attachment for diagram...
  9. T

    Tension in the block string

    4.0 kg block A and 6.0kg block B are connected by a string of negligible mass. Force a Fa = 12N acts on block A; force B Fb = 24N acts on block B. What is the tension in the string. I was able to draw FBD and lists all the forces acting on A and B, but what I don't understand is the tension T...
  10. B

    Block pulled on horizontal surface -w/friction-

    Homework Statement A box weighing 80N is pulled along a horizontal surface by a force of 15 N which is directed at 20° above the horizontal. If the box started from rest and the coefficient of friction is 0.15, find the kinetic energy and velocity of the box after it traveled a distance of...
  11. A

    Friction Problem - block on an incline (serway)

    Hi, I've been trying to nail this problem but I'm not sure if I'm stating it correctly: 1. "A block weighing 75.0 N rests on a plane inclined at 25.0° to the horizontal. A force F is applied to the object at 40.0° to the horizontal, pushing it upward on the plane. The coefficients of static...
  12. L

    Energy Conservation/Potential Energy - block on a hill

    Homework Statement A 2.8kg block slides over a smooth icy hill. The top of the hill is horizontal and 70m higher than its base. The 70m plateau is 80m from the base of the hill. What is the minimum speed the block must have so that it will not fall into the pit on the far side of the hill...
  13. P

    Why is it important to make sure the string attached to the block level?

    Homework Statement In a friction lab to determine the static and kinetic coefficient of friction, there is a block on a flat slope attached to a string which pulled down by a hanging mass. The lab question is: Why is it important to make sure that the string attached to the block is level...
  14. S

    Finding the speed of a block moving on an incline

    I apologize i do not have a picture to show. 1. Homework Statement [/b] A block of mass 250g is at rest on an incline that makes an angle of 30 degrees to the horizontal. The coefficient of kinetic friction between the block and the plane is 0.10. The block is attached to a second block...
  15. E

    Upward velocity of a block on a string

    Homework Statement The force constant of a spring is 600 N/m and the un-stretched length is 0.72m. A 3.2kg block is suspended from the spring. An external force slowly pulls the block down, until the spring has been stretched to a length of 0.86m. The external force is then removed, and the...
  16. P

    Calculating Acceleration on a Ramp with Friction

    [b]1. What is the acceleration of the 20 kg block if the block is being pulled with a force of 150 N at 60 degrees above the X+ axis and there is a frictional force of 20 N acting on the block? [b]2. F=ma, Fcos(theta). [b]3. I did (150)cos(60)=(20)a ---> 75=20a ---> a=3.75 m/s...
  17. S

    Block and wedge system all details

    Homework Statement okay this isn't really a question, but i didnt knew where to post it, tell me if it has to be posted somewhere else. a pic of the diagram would help a lot. A block is kept on the top of a wedge of angle alpha, can u explain what all happens, keeping all surfaces...
  18. J

    Rope with mass pulling a block

    Homework Statement Homework Equations f = ma The Attempt at a Solution I need help with all parts of this problem, but here are my comments on part a and c: a) the block has its normal force vector pointing up and its weight vector pointing down. the tension of the rope is pulling it to...
  19. Z

    Finding mass of a block tethered to an incined block above

    Homework Statement Two blocks are connected by a string (through a frictionless massless pully) block 1 is on an inclined plane, while block two is hanging from the other end of the string. m1 = 20kg, theta =53.1, friction between the block and the inclinde is \muk =.4 what is m2 such that...
  20. E

    Solving for tan γ: Understanding the Relationship between d/l and h/l"

    This is more a question about how the problem is written, rather than a question about how to do the problem Why do they ask for tan γ in terms of d/l and h/l, rather than d and h? Is there some relation that I'm just not seeing? I'm pretty sure I know how to do the problem in terms of d...
  21. C

    Mass of Block 1 & Static Friction Info for Block-Table System

    Block 1 as shown in the link below(url) has a mass of 10.3 kg. The coefficient of static friction between the block and the table is μs = 0.36 and the coefficient of kinetic friction is μk = 0.336. a) What should the mass of the second block be so that m1 is just on the verge of sliding? I...
  22. B

    Friction problem of a 6kg block

    A 6 kg block rests on a horizontal table, attached to a 5 kg block by a light string as shown in the figure. The acceleration of gravity is 9.81 m/s2 . A) What is the minimum coefficient of static friction such that the objects remain at rest? I already got part A which is 0.833, but...
  23. M

    How to find mass of block from static friction

    no longer needed
  24. C

    Block sliding Down; find kinetic coefficient

    Homework Statement A block is at rest on a plank whose angle can be varied. The angle is gradually increased from 0 deg. At 25.7°, the block starts to slide down the incline, traveling 3.50 m down the incline in 1.50 s. Calculate the coefficient of static friction between the block and the...
  25. S

    Finding the weight, work, and normal force of a block

    Homework Statement 4 questions: 1. A block of mass M=2.6 kg is dragged over a horizontal surface by a force F=22.0 N. The block is displaced a distance d=10.0 m, the friction force Ff is 3.1 N. What is the weight of the block in Newtons? Use 10 m/s2 for g. 2. A block of mass M=1.0 kg is...
  26. khurram usman

    Pressure on block immersed in water?

    i was solving a problem based on archimedes principle. but got confused whilr determinig the pressure. well the situation was that a block is immersed in water. the height of water column above it is .05m. the blocks side is .02 m and its base area is 25cm^2.and the height of water below the...
  27. K

    Homework help: Harmonic Motion of a Spring and Block System

    Homework Statement Part 1: A 0.1 kg block attached to a spring of force constant 17.2 N/m oscillates with an amplitude of 16 cm. Find the the maximum speed of the block. I solved this part using the equations for angular frequency and max velocity. Part 2: Find speed of the...
  28. E

    Thermodynamics and Entropy- reservoir and block problem

    Homework Statement A 382 g block is put in contact with a thermal reservoir. The block is initially at a lower temperature than the reservoir. Assume that the consequent transfer of energy as heat from the reservoir to the block is reversible. Figure 20-22 gives the change in entropy ΔS of the...
  29. D

    Confirm/Refute: Block A Will Drag Block B to the Left

    Homework Statement In a simulation of machinery at a mine site, blocks of wood were used as shown in the following experimental set-up in which the two blocks – A and B – both of mass 15 kg are joined by a string over a frictionless pulley. Block A rests on a frictionless incline of 30º...
  30. D

    Mass on a friction less incline. What force is needed to stop the block from sliding.

    Homework Statement A block with mass 10kg rests on a smooth, friction less ramp that is inclined at an angle of 45 degrees with the ground. How much force must be applied in the direction parallel to the ground to prevent the block from sliding down the ramp? IT TURNS OUT THAT THE...
  31. D

    Mass on a friction less incline. What force is needed to stop the block from sliding.

    Homework Statement A block with mass 10kg rests on a smooth, friction less ramp that is inclined at an angle of 45 degrees with the ground. How much force must be applied in the direction parallel to the ground to prevent the block from sliding down the ramp? IT TURNS OUT THAT THE...
  32. W

    Control Engineering: Block Diagram

    Hi guys, this is quite an inbetween question , not really homework but still theory. http://img850.imageshack.us/img850/1290/81696653.jpg Came across this diagram and was wondering if the arrow (in blue box) can be ignored ? Quite irritated by it now since I can't be sure how I should...
  33. R

    How to Model Complex Equations in Simulink?

    [b]1. I am working on a project to achieve maximum power output from a motor using the MEPT (MAximum Energy Power Point) algorithm for a small scale compressed air energy storage system. In the equation to attain efficiency, I am using simulink. I am not able to form the equation for this part...
  34. A

    Speed Of A Bullet Before It Strikes A Block Of Wood

    Homework Statement A 10g bullet strikes and becomes embedded in a 0.200kg block of wood placed on a horizontal surface just in front of the gun. If the coefficient of sliding friction between the block and the surface is 0.4 and the impact drives the block a distance of 8m before it comes to...
  35. A

    Fully labelled block diagram of 3-bit ‘Flash Encoding’

    Homework Statement Draw a fully labelled block diagram of a 3-bit ‘Flash Encoding’ analogue to digital converter (ADC) and explain how the device converts an analogue voltage into a 3-bit binary number. The Attempt at a Solution anyone know how to do this or have any sources would be...
  36. N

    Shear Stress In A Wooden Block

    Homework Statement Homework Equations \sigma = F/A The Attempt at a Solution I understand that I should evaluate the different forms of stress to find different values of the ultimate load. I also understand that I should choose the smallest value among them since anything...
  37. O

    Lead Block inside 52' US-type Trailer Experiement

    Can someone calculate the weight of the object and what would most likely happen in the following experiment that I have always been curious about: Imagine you have a brand new 52-foot standard refrigerated cargo trailer mounted on a brand new standard heavy duty sleep cab tractor (i.e., an...
  38. E

    Matrix multiplication preserve order Block matrix

    Hello, If I have block matrices A,B,C and D all of which are non singular would this relationship hold; my main concern is preserving order of matrix multiplication: if ADB=C then AD=B^-1C D=B^-1CA^-1 D^-1 = (BC^-1A) Also is it okay to assume the inverse of a block...
  39. P

    Hallo folks I'm new (kid on the block).

    Hi, I like it here! This lounge it's cozy. It's magic too, because it brings out the best out of scientists. (any mad scientist around? with no sense of humour? :biggrin:) I looked around and I have a question for you: why should a scientist hide his age? Probably now you can...
  40. A

    Do carbon block water filters actually remove some fluoride?

    Hi! This is my first post on physicsforums. I wasn't sure if it belonged here or in the Chemistry forum, but just picked here. I am trying to figure out if my drinking water filter system removes some fluoride from my water. (I know it doesn't remove all as it's not specifically a fluoride...
  41. J

    Mass of water displaced by a block

    Homework Statement A block is suspended from a scale and then lowered into a bucket of water. The density of the water is 1 gm/cm3. The initial reading on the scale is 19N and one complete revolution of the scale is a change of 10N. (The block is completely submerged after one complete...
  42. J

    Finding coefficient of fuzzy block and dynamics cart.

    Homework Statement Calculate the coefficient of friction between a fuzzy block and dynamics cart? This is a Lab task so I have all the materials but I don't know where to start. Homework Equations u=ff/fn uk=fk/fn us=fs/fn The Attempt at a Solution I tried using the formulas...
  43. J

    Block with friction on acc' wedge

    A block rests on a wedge inclined at an angle theta. The coefficient of friction between the block and the plane is mu. (a) Find the maximum value of theta for the block to remain motionless on the wedge when the wedge is fixed in position. (b) The wedge is given horizontal acceleration a, as in...
  44. J

    Acceleration of block on acc' wedge

    A 45 deg wedge is pushed along a table with constant acceleration A. A block of mass m slides without friction on the wedge find its acceleration. Clue if A=3g then \ddot{y} = g I'm not sure of the forces on the block, if A is parallel to the base of the wedge then what component of A acts...
  45. C

    Ice block on inclined plane- easy problem

    Ice block on inclined plane-- easy problem! I'm pretty sure I did this correctly, but my answers are different from those given in the back of the book (which our TA warned us were frequently incorrect), so I thought I'd ask you guys if I made any obvious mistakes. Homework Statement A...
  46. H

    Conservation of Energy speed of block

    A block starts at rest and slides down a frictionless track except for a small rough area on a horizontal section of the track (as shown in the figure attached for#007). It leaves the track horizontally, flies through the air, and subsequently strikes the ground. The acceleration of gravity is...
  47. T

    Thermodynamics: heat needed to melt block of a metal

    Homework Statement the latent heat of fusion for this metal is 500Cal/kg. The latent heat of vaporization is 600Cal/kg and specific heat of the liquid metal is 500C/kg K. How much heat is needed to melt an 8kg block of this metal when its temperature is exactly at the melting point...
  48. T

    How Does Damping Affect Oscillation Amplitude and Frequency?

    Homework Statement The drawing to the left shows a mass m= 1.8 kg hanging from a spring with spring constant k = 7 N/m. The mass is also attached to a paddle which is emersed in a tank of water with a total depth of 27 cm. When the mass oscillates, the paddle acts as a damping force given by...
  49. A

    Block of mass Rotational Problem

    Homework Statement A block of mass m1 = 2.00 kg and a block of mass m 2 = 6.00 kg are connected by a massless string over a pulley in the shape of a disk having radius R = 0.250 m and mass M = 10.0 kg. These blocks are allowed to move on a fixed block – wedge of angle 30.0°, as shown in...
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