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. T

    Speed of block as cylinder reaches bottom of circular track.

    Homework Statement A block of mass M=2kg with a semicircular track of radius R=1.1m rests on a horizontal frictionless surface.A uniform cylinder of radius r=10cm and mass m=1kg is released from rest from the top most point .The cylinder slips on the semicircular frictionless track.The...
  2. O

    Force of 5N applied to 5kg block on table w/ μk = .1

    Homework Statement A force of 5N is being applied to a 5kg block is on a table. The μk = .1. What is the velocity of the block?Homework Equations (μk)(Fn) = Ff The Attempt at a Solution (.1)(50N) = 5N of friction. The net force is 5N - 5N = 0NFrom here, I believe it is impossible to find...
  3. siimplyabi

    What is the acceleration of each block?

    1. The problem statement, all variables and given/known data A pair of blocks are connected by a massless rope and placed on a frictionless surface. The diagram shows the situation at the instant the blocks are released. The left side has a mass of 35 kg and an incline of 25 degrees to the...
  4. wein7145

    A horizontal force of 100 N is applied a block solve this

    Homework Statement 1) A block lies on a horizontal friction-less surface. A horizontal force of 100 N is applied to the block giving rise to an acceleration of 3m/s^2. (a) Determine the mass of the block. b)Calculate the distance the block will travel if the force is applied for 10s...
  5. Dale

    Insights PF's policy on Lorentz Ether Theory and Block Universe - Comments

    DaleSpam submitted a new PF Insights post PF's policy on Lorentz Ether Theory and Block Universe Continue reading the Original PF Insights Post.
  6. P

    Determining the Net Force on a Wedge and Block System

    Homework Statement [/B] For the situation shown in the diagram, the block of mass m remains in place on the sloping front of the accelerating wedge, even though that sloping front is frictionless. Given these values, M = 20.0 kg, m = 4.00 kg, and theta= 34.0, calculate the net force acting on...
  7. T

    Dangling block attached to rotating block

    I’m an applied math grad student and I wanted to check my conceptual understanding of what I thought was a basic mechanics problem. You have two blocks connected by a weightless, frictionless string passing through a tiny hole in a table. On the table, one block (mass m) rotates without friction...
  8. V

    Find the initial acceleration of the block

    Homework Statement Homework EquationsThe Attempt at a Solution The question says block B has negligible mass ,which means particle will be effectively in free fall i.e acceleration would be 'g' . But then it is given a horizontal velocity i.e it has centripetal acceleration ac about the...
  9. M

    [Physics waves] Spring and Block on inclined plane

    Homework Statement A block weighing 9.81N oscillates on a plane inclined of 60 degrees attached to a spring whose constant point is k=100N/m and the length is to equilibrium l0 = 0.6 m. While the block goes to the top losing speed , a timer is started ( to t0 = 0) when the block passes through...
  10. O

    Force of hand on block = F of block on hand, not adding up?

    Lets say I apply a force of 20N to a 10kg block on a frictionless table. Then the acceleration of the block is F= ma = F/m = 2m/s^2 = a. Then, supposing I am standing on the ground with real world friction such that I am not accelerated in the opposite direction when I push the block that is...
  11. E

    What Is the Work Done by Normal Reaction Forces on an Inclined Plane System?

    Homework Statement A block of mass m is released from rest on a smooth inclined plane (wedge). The wedge itself is resting on a smooth horizontal surface. The block undergoes a vertical displacement of h. Assume that the height of the incline is h and the length of the incline is h cosec θ...
  12. M

    Find the final velocity of the block

    Homework Statement So here is the problem, There is a .03kg block that is in an inverted cone, the cone has a slant length of 15 cm and a radius of 4 cm, and the coefficient of friction is .35. The block rotates around the inside of the cone, seamlessly, until it hits the bottom of the cone...
  13. O

    Easy statics problem -- Block being hoisted by a pulley and rope

    I drew a FBD about point A and came up with the two equations: ∑Fx=0 20sinθ - T-ab(cos70)=0 ΣFy =0 -20cosθ + T-ab(sin70) -20=0 My answer is not coming out so I either messed up on the FBD or the equations, some help would be appreciated. I'm on 3-10 by the way.
  14. N

    Block and disk on double inclined plane

    Homework Statement https://courses.edx.org/asset-v1:MITx+8.MechCx_2+2T2015+type@asset+block/rolling_quiz_3.svg A block of mass mb and a disk of mass md and radius r are placed on a symmetric triangular slope connected with a massless string over a massless pulley as shown above. The string is...
  15. Z

    Momentum problem -- Two bullets fired into a block

    Homework Statement A 7.00-g bullet, when fired from a gun into a 1.00-kg block of wood held in a vise, penetrates the block to a depth of 8.00 cm. This block of wood is next placed on a frictionless horizontal surface, and a second 7.00-g bullet is fired from the gun into the block. To what...
  16. C

    Simulink Memory Block: Integration & Inherit Sample Time

    Ok,here is the problem. The block holds and delays the input signal for some time but what is a major integration step?Where is the integration?And if we choose inherit sample time,from where does the block inherit sample time?
  17. Titan97

    Finding Normal Reaction between Wedge and Block

    Homework Statement A block of mass m is kept on a smooth wedge of angle α and mass M which is in turn kept on a smooth floor. When the system is released from rest, calculate the force exerted by block on the wedge. Homework Equations None. The Attempt at a Solution Let the block a have a...
  18. N

    Block collision attached to spring

    Homework Statement A block of mass m is attached to a spring with a force constant k, as in the above diagram. Initially, the spring is compressed a distance x from the equilibrium and the block is held at rest. Another block, of mass 2m, is placed a distance x/2 from the equilibrium as...
  19. N

    How Far Do Colliding Blocks Slide on a Spring?

    Homework Statement A block of mass m is attached to a spring with a force constant k, as in the above diagram. Initially, the spring is compressed a distance x from the equilibrium and the block is held at rest. Another block, of mass 2m, is placed a distance x/2 from the equilibrium as...
  20. T

    Diagram for Wooden Block Friction Problem

    Homework Statement A wooden block of mass M resting on a rough horizontal floor is pulled with a force F at an angle θ with the horizontal. If μ is the coeeficient of kinetic friction between the block and the surface, then acceleration of the block is? Homework EquationsThe Attempt at a...
  21. stacope32

    A block sliding down a ramp lab (with friction)

    Homework Statement A block of 55 g is sliding down a ramp of 35 degrees of inclination. The hypotenuse of the ramp is 63 cm and the height is 36 cm. vi = 0 as the block starts at rest. Homework Equations vf = vi + a(t) d = vi*t + (a(t)^2)/2 kinetic energy = (mv^2)/2 The Attempt at a Solution...
  22. lonely_nucleus

    Do capacitors block unwanted ac frequencies in the wires?

    I have been studying capacitors and inductors recently and I have seen this video. I have a few questions about capacitors and inductors. Capacitors: 1.how do capacitors discharge? 2. What happens when you apply direct current through a capacitor? 3.Do capacitors only allow certain...
  23. Sarah00

    Two block on each other with friction

    Homework Statement Homework Equations F = ma Ffr = u * Fn The Attempt at a Solution After drawing FBD For m2: we have only friction force in horizontal axis so Ffr = ma ==> u * Fn = ma ==> u * mg = ma ==> u * g = a ==> a = 0.5 * 10 = 5 m/s2 Now, moving to m1: F - Ffr = ma ==> F - u Fn = 10...
  24. K

    Why is the net force on block A twice that on block B?

    www.webassign.net/serpop/p7-47.gif In the figure that I've posted in the link above, it is assumed that both blocks are initially held at rest and then released. Why does block A move with twice the speed of block B?
  25. V

    Find Acceleration of Wedge with Rope Pulled by Constant Force T

    Homework Statement [/B] In the attached picture, the rope is being pulled by a constant force T. All the surfaces are smooth. The pulley and the rope are massless and frictionless. Find the acceleration of the wedge.(use g=10ms-2) Homework EquationsThe Attempt at a Solution The normal force...
  26. andyrk

    Oscillating Spring Block System inside elevator

    A particle that hangs from a spring oscillates with an angular frequency of 2 rad/s. The spring is suspended from the ceiling of an elevator car and hangs motionless (relative to the car) as the car descends at a constant speed of 1.5 m/s. The car then suddenly stops. Neglect the mass of the...
  27. J-dizzal

    One dimensional inelastic collision; bullet through block.

    Homework Statement In the figure here, a 12.8 g bullet moving directly upward at 930 m/s strikes and passes through the center of mass of a 8.3 kg block initially at rest. The bullet emerges from the block moving directly upward at 520 m/s. To what maximum height does the block then rise above...
  28. N

    Static friction in two block problems

    Doubt - Force cannlt exceed limiting friction for a block to remain at rest on ground. However for to blocks to move together, it becomes more than limiting friction, yet only static friction is acting on the blocks? Which moves the lower block. How can it be more in this case? Relative...
  29. J-dizzal

    Newton's 2nd law question -- pushing a block up an inclined ramp....

    If a constant force is applied to an object and the force is pushing the object up a inclined ramp with constant velocity what is the acceleration if mass is unknown? F=ma F=m (1m/s^2) If i apply this equation then acceleration is 1m/s^2. Am i applying this formula correctly? thanks
  30. M

    Forces and Friction on a Block and a Beam

    Homework Statement A block of mass M = 1 kg is placed between a vertical wall and the end of A beam mass m = 10 kg . If μ S = 0.6 A , determine the minimum value of the angle θ min θ for which the block remains in equilibrium and the coefficient of friction Static B μ S corresponding to prevent...
  31. E

    Block Slides Down a Movable Ramp....

    Homework Statement A block of mass m is held at rest at height h on an inclined plane of mass M, placed on a horizontal surface as shown. The block is then released. Find the speed of the inclined plane v_{I} just as the block slides off of it. Neglect all frictional forces. Express your...
  32. Drakkith

    What is the work-energy theorem for a block sliding on a frictionless incline?

    Homework Statement A mass m = 16 kg is pulled along a horizontal floor, with a coefficient of kinetic friction μk = 0.09, for a distance d = 7.6 m. Then the mass is continued to be pulled up a frictionless incline that makes an angle θ = 34° with the horizontal. The entire time the massless...
  33. M

    Friction in a 3 block and pulley system

    Homework Statement A block of mass m1 is on top of a block of mass m2. Block 2 is connected by an ideal rope passing through a pulley to a block of unknown mass m3 as shown. The pulley is massless and frictionless. There is friction between block 1 and 2 and between the horizontal surface and...
  34. Amat3r

    How Do You Model a Torsion Spring in a Pendulum's Lagrangian?

    Hello! I'd like to ask for help with one problem :) thank you in advance. 1. Write the equations for kinetic and potential energy for the pendulum with rectangular prism of size a*b*c (width, length, depth). With the Lagrange's equation get the equation of motion. The block is homogeneous...
  35. Ackbach

    MHB Electric Field of Thick Infinite Sheet of Charge

    It is known that a non-conducting sheet of charge (charge on only one "side") has electric field magnitude $$E=\frac{\sigma}{2\varepsilon_0},$$ where $\sigma$ is the surface charge density in Coulombs per square meter. Suppose now that we have an infinite sheet, but it has a thickness $\ell$ to...
  36. Drakkith

    Acceleration of a Block Down a Ramp

    Homework Statement [/B] A block with mass m1 = 9.2 kg is on an incline with an angle θ = 36° with respect to the horizontal. For the first question there is no friction, but for the rest of this problem the coefficients of friction are: μk = 0.33 and μs = 0.363. 1.) When there is no friction...
  37. Canutej24

    Is Time an Illusion? Exploring the Concept of a Block Universe at 13 Years Old

    I'm 13, so I was reading Discover and I read something about a "block universe" and I thought it was a bunch of hogwash... here is how I see it... Time is the same for everybody its just how people perceive it that makes people think its an illusion... any feedback? Thanks!
  38. K

    Where does band index come from in block wave functions?

    Can you show me as explicitly as possible through equations?
  39. minimario

    Friction Forces Between Stacked Blocks: Determining Direction

    Homework Statement Homework Equations F = ma The Attempt at a Solution When drawing a FBD for block 1, I couldn't figure out if the friction force between the blocks was toward the left or toward the right. Similar situation on block 2. How would I determine this?
  40. J

    How do I reduce the outer loop in the first question with 3 inputs?

    Homework Statement I have got 2 questions like this and I'm struggling any help would be much appreciated please. Thanks Homework EquationsThe Attempt at a Solution
  41. L

    Object sliding down a block on a scale

    Homework Statement A 200g hamster sits on an 800 g wedge shaped block which in turn rests on a spring scale. An extra fine lubricating oil is sprayed on the top surface of the block, rendering it entirely frictionless, causing the hamster to slide down. Friction between the block and the scale...
  42. mooncrater

    Reason for the obvious movement of a block

    1. Homework Statement Consider the given system. It is obvious that the weight of the block will lead the system to move in the leftward direction. But the reason for that is not clear to me. Homework Equations Using the FBD of the block(B): ##mg-T=ma## where ##a## is assumed its downward...
  43. AdityaDev

    Finding acceleration of block connected to pulley with mass

    Homework Statement Homework Equations a=Rα The Attempt at a Solution Free body diagrams: For larger pulley, TR=Iα ⇒ T=½MRα If this pulley rotates by some amount suchat x length of rope becomes free, and if I hold the smaller pulley at rest, then this extra length of rope comes bellow the...
  44. G

    Finding Impulse Response from Block Diagram

    Homework Statement Where $$v = y - bu$$ It's given that the transfer function is $$h(t) = b u(t) + v(t) = b \delta(t) + e^{at}b \mu(t)$$ Homework EquationsThe Attempt at a Solution I can't seem to figure out how the impulse response above was found. I understand that the impulse response is y...
  45. J

    Motion of System in Inertial Frame: Analysis & Constraint Finding

    Homework Statement Additional instructions: Analyze the motion of the system in an inertial frame of reference fixed to the table on which M1 slides. You can't analyze the system with Newton's Laws in the frame of M1 because M1 will accelerate, and that frame will not be inertial. When you...
  46. JesseJC

    Inclined plane with block and cylinder, pulley with mas

    Homework Statement Find the acceleration of the system if the mass m1 is a disk with radius R rolling down an incline which makes an angle theta with the horizontal, and the disk is connected to a pulley with mass M and radius R, which is connected to a block m2 hanging from that pulley. The...
  47. M

    Randomized Complete Block Design - Scheffe Multiple Comparison

    Homework Statement I'm working on a problem in Design and Analysis of Experiments by Dean and Voss. It's Chapter 10 question 11 part c. We have an experiment with 2 treatment factors (each with three levels) and 1 blocking factor (with four levels. It's a randomized complete block design so...
  48. DavideGenoa

    Slipping block on a slipping ramp: final speed

    Hi, friends! A block having mass ##m## frictionlessly slips from height ##h## on a ramp of mass ##M##, which has an angle ##\theta## with the floor, where it slips with no friction. I would like to prove that, as my book says, the ramp's speed when the block leaves it is...
  49. Y

    Block moving towards movable wedge

    Homework Statement A small block with mass m is moving towards a stationary slope with velocity v, angle θ and height h, suppose all surfaces are frictionless. Suppose the slope has mass M and it is able to move freely on the ground, what is the minimum initial speed for the block to be able...
  50. W

    Which Equation Best Describes the Block's Height After a Bullet Impact?

    Homework Statement Which equation could adequately be used to determine how high the block goes after being hit by the bullet (a height h)? (see figure) (m+M)gh+ksh=1/2(m+M)V^2 (m+M)gh+1/2ksh^2=1/2(m+M)V^2 (m+M)v+ksh=(m+M)V Homework Equations KE=1/2mv^2 Ugrav=Mgh PE of spring = 1/2ks(s^2...
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