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. A

    Maximum Compression for a Block on Spring

    Hi everyone, just a quick question.. I tried this problem using Newtons laws, not conservation of energy, and I got an answer exactly half of what the correct answer is, and I'm not sure why. Here is what I did: Net force = zero once the spring is compressed, therefore mg - kx = 0 mg = kx...
  2. brotherbobby

    What is the maximum tension and friction force for a block held on an incline?

    (a) Ridiculously simple though it looks, I can't see how the string will be tight. One of the two has to be true. (1) The static friction ##f_S = mg \sin\theta = 25\times 10\times \sin 30^{\circ} = 122.5\; \text{N} ##. The maximum static friction ##f_S = \mu mg \cos \theta = 0.6\times 25\times...
  3. Mimosapudica

    Calculating the power delivered when a block of mass m slides along

    Force along the horizontal would be T cos(theta) Frictional force (which is in the opposite direction )= μmg So net force in the direction of velocity = Tcos(theta)-μmg P= [Tcos(theta)-μmg]v But this is not so, the right answer is given to be Tvcos(theta). Why should we not consider the...
  4. Like Tony Stark

    Find the distance that the block has to move so that....

    I called the block ##A## and ##B## the cylinder. For ##A##, in the non inertial system I wrote ##x) Fr_d -F=0## ##y) R-W_1=0## Where ##Fr_d## is the kinetic friction and ##R## the normal force on ##A## Then, I know that: ##a_{B/A}=a_B-a_A## ##0=a_B -a_A## ##a_A=a_B## ##v_{B/A}=v_B-v_A##...
  5. Like Tony Stark

    Acceleration acting on a block lying on a wedge (non-inertial frame)

    I have some difficulties trying to understand non-inertial frames. I have problems to notice the acceleration in these cases, from an inertial reference frame and from non inertial refrence frame. Consider the first case, if I'm on the wedge, I see that the block doesn't move so there's no...
  6. Like Tony Stark

    Acceleration and tension of a block on an inclined plane

    I considered the downwards direction and left direction as negative. For ##m_1##, Newton's equations are: ##x) Fr + W_x - T=0## ##y) N - W_y =0## For ##m_2##: ##y) T - W =0## Then, if I replace the data, I get ##T=22.2 N## and then ##m_2=2.2 kg##. With that, for the second question ##m_2=4.4...
  7. Like Tony Stark

    Forces acting on a block which is lying on another block

    Well, I'm having trouble with the free body diagrams. For ##A## we have ##y)## weight, normal force, contact force with ##B##, ##F . sin(36.8°)##. And the acceleration is ##0## because we want to calculate the maximun force before moving. ##\Sigma \vec F = m . a_y## ##\vec N_A + \vec F ...
  8. vcm1992

    Block on a Plane (Classical Mechanics)

    I've taken intro to classical mechanics, but am really not sure about how this example calculates the friction force and the normal force...I usually break down the force vector into components, and I understand that this is probably a much more simple way to calculate the perpendicular and...
  9. E

    This is what happens to an aluminum block when it hits...

    This is what happen to an aluminum block when a 0.5 ounce piece of plastic hits it at a speed 15,000mph in space. That's some serious impact! Just imagine what a heavier object could do traveling at the same speed.
  10. jisbon

    Forces/Dynamics: A block sliding on a plate

    Question as follows: My answer/explanation: Force needed to make block slide = static friction between block and plate. So friction = normal of block * static friction = (0.5∗9.8)∗0.9=4.41N(0.5∗9.8)∗0.9=4.41N My thoughts/wrong answer probably?: after block slips, plate experience kinetic...
  11. naji0044

    Inelastic collision problem: Bullet striking a wood block

    Hey everyone I'm struggling on the last part of this assignment. I need to find the total work done by the block and the bullet, when the collision happens. The informations is: mblock=0.3 kg mbullet=0.01 kg vg=700 m/s Height=0.72m The final speed after the collision is vf=22.6 m/s and the...
  12. kileigh

    How to find the number of oscillations a block goes through

    This is the image provided with the problem, the values given include: d= 4.00 m, the mass of block one=0.200 kg, speed of block one=8.00 m/s, the period of oscillations for block two without friction=0.140 s, and the spring constant= 1208.5 N/m. I know how to solve the oscillations if block...
  13. Kaushik

    Does the block move along the pink dotted lines

    Does the block move along the pink dotted lines as attached in the figure below? I tried to draw the FBD of the small block ##m ## at the lowermost point which is also attached below.(The direction of ## v_0 ## is actually tangential) Is the figure above correct? If not, why?
  14. Quantum Alchemy

    B Questions about Einstein and the Block Universe

    I find this subject fascinating. Einstein said the distinctions between past, present and future is just a persistent illusion. I was watching a special with Brian Greene and other Physicist who think we do live in a Block Universe and they explained it very well. Here's my question. Say there...
  15. Benjamin_harsh

    Can a 10N Force Overcome Friction to Move a 10kg Block?

    A block of mass ##10kg## rests on a horizontal floor. The acceleration due to gravity is ##9.81 m/s^{2}##. The coefficient of static friction between the floor and the block is ##0.2##. A horizontal force of ##10N## is applied on the block as shown in the figure. The magnitude force of friction...
  16. Kaushik

    Determine the acceleration of block m1 in this wedge-pulley system

    The equations i got are attached below. Is it right? If yes what should we do after this. I tried solving the equations, but i did not arrive at the solution.
  17. F

    MHB Find Glass Thickness to Block 25% of Light in Sunglasses

    The intensity, I of light in lumens, passing through the glass of a pair of sunglasses is given by the equation I(x) = I0 (0.8)^x , where x is the thickness of the glass in millimetres and I0 is the intensity of light entering the glasses. How thick should the glass be so that it will block 25%...
  18. Benjamin_harsh

    Please explain this doubt about a block sliding question

    Sol: ##Mg.sinθ - μMg.cosθ = ma## ##a = g.sinθ - μg.cosθ## Now ##S = ut + \large\frac{1}{2}\normalsize at^{2}## but ##u = 0## ##t = \large\sqrt\frac{2s}{a} = \sqrt\frac {2s}{gcosθ(tanθ- μ)}## My questions: What is the meaning of " PQ = s" in the question? How ##t = \large\sqrt\frac{2s}{a}...
  19. Shivam

    What is the kinetic energy of the block when it is moved 2cm.

    My attempt at the solution... I only have problem in solving part a) 1) i calculated the spring force actingbon the table block and it is greater than the frictionnand tension force acting in the opposite direction, so by that the block will move in left. 2) now i found that which forces are...
  20. Shivam

    Find Velocity of the wooden block at t=4 sec

    Here's the given F-t graph My Attempt... Fsmax=10N & Fk= 5N I made equatiom F=5t-5 ( by seeing Force force and Counteracting kinetic friction) reduced the formula to a=(5t-t)/2 wrote a=dv/dt and solved it but got wrong answer.
  21. V

    Connected system of a bullet and a block

    This is task from my textbook and it does not provide us with an answer. So I cannot verify if I did mistake. Can someone double check, please? My solution: ##E_{k_{0}} = \frac{(m+M)v_{0}^2}{2} \quad \land \quad U = \frac{kx^2}{2}## ##E_{k_{0}} = U## ##\Longrightarrow (m+M)v_{0}^2 = kx^2##...
  22. Lone Wolf

    Conservation of energy for a block on an incline plane

    Let v be the speed of the block and x elongation of the spring beyond the equilibrium point. Initially, v = 0 and x = 0. At the maximum elongation, the block also has v = 0, it has moved a distance equal to x (parallel to the plane) and the variation of height is equal to -x⋅sin(53°). W(FNC) =...
  23. TheDudeTR

    A contrete block released from the rest

    this is the question and solution given in the book solution i made below. only difference is i took x as opposite side that given in the book and wrote F=ma equation that way. as a result the left side of equation (3) directly turned negative. that caused difference in result but why? i mean...
  24. N

    A Block Diagonalization - Representation Theory

    How does one go about finding a matrix, U, such that U-1D(g)U produces a block diagonal matrix for all g in G? For example, I am trying to figure out how the matrix (7) on page 4 of this document is obtained.
  25. H

    What is the Well-Known Feedback Expression for Block Diagram Manipulation?

    Hello I hope someone can help me, as i am kinda stuck for the moment. As you can see, the assignment states that I need to find the poles from the closed loop transfer function. I plan on doing so, by using block diagram reduction method. This is as fare as I've come, and can't come...
  26. H

    I Pole Identification Using Block Diagram Reduction

    Hello I hope someone can help me, as i am kinda stuck for the moment. As you can see, the assignment states that I need to find the poles from the closed loop transfer function. I plan on doing so, by using block diagram reduction method. This is as fare as I've come, and can't come further...
  27. Caio Graco

    Static friction force: Consider a block on a sheet of paper....

    Consider a block on a sheet of paper. If the sheet is pulled without sliding the block, who has done work on the block (since it has undergone a kinetic energy variation)? I can not see another force doing work other than the static frictional force on the block.
  28. C

    Work Problem -- Wood Block Sliding into a Spring

    W_net = Integral from 0 to 0.70 meters [ - F_spring - F_friction ] = 1/2 * (-k) * x^2 - mu * mg * normal force * x = 1/2 * (-325N/m) * (.70)^2 - 0.250 * 6kg * 9.81m/s^2 * 0.70 - 0 = - 89.93 Joules Is this correct and am I setting this whole thing up correctly? The negative signs have me...
  29. P

    I Is the Minkowksi/Einstein Block Universe theory science?

    Hermann Minkowski (Einsteins math instructor and a mathematical physicist himself): The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth space by itself, and time by itself...
  30. N

    I Block Diagonal Matrix and Similarity Transformation

    I am looking at page 2 of this document.https://ocw.mit.edu/courses/chemistry/5-04-principles-of-inorganic-chemistry-ii-fall-2008/lecture-notes/Lecture_3.pdf How is the transformation matrix, ν, obtained? I am familiar with diagonalization of a matrix, M, where D = S-1MS and the columns of S...
  31. M

    How far does the block slide? (work, spring, incline)

    Homework Statement The system is released from rest with no slack in the cable and with the spring stretched 225 mm. Determine the distance s traveled by the 3.2-kg cart before it comes to rest (a) if m approaches zero and (b) if m = 2.5 kg. Assume no mechanical interference and no friction...
  32. CVRIV

    Issue with book's solution for a block projected up an....

    Hello everyone:) I'm having an issue with an example problem in the book I'm using. I attached a pic of the problem and the book's solution. The issue I'm having is that I have no idea how the book got the velocity it did via the solution it presented. When I worked out the problem myself...
  33. R

    Why is my thinking incorrect? -- Block and spring driven by a motor

    Homework Statement An oscillator consists of a block attached to a spring (k=400n/m). At some time t, the position (from equilibrium), velocity, and acceleration of the block are x= .100m, v= -13.6m/s, a= -123m/s^2. What is the frequency? mass of block? amplitude. Homework Equations position...
  34. M

    Studying Overcome the "Publication Block": Advice for a 5th Year PhD Student

    Hi all, Hopefully this is the right section of the forum to post in! I am a 5th year PhD student in physics at a prestigious university in the US. First 2 years I was taking classes and working in particle physics. On my 3rd year I transitioned to astrophysics. So in terms of the dedicated...
  35. Abhishek11235

    Number of collisions with a block

    The problem is given in David Morin's Classical mechanics. Now, I jumped to solve part b of question. To find the number of bounces,we note that mass losses momentum of -2mV per bounce(This can be worked out from conservation of momentum and energy). Now initial momentum was MV. Then since per...
  36. J

    Determine the friction force in a stacked block scenario

    Homework Statement Assume that block A which has a mass of 30 kg is being pushed to the left with a force of 75 N along a frictionless surface. What is the friction force of block A on block B if the block B has a mass of 24 kg and is accelerating at 0.50 m/s2 to the right relative to the block...
  37. Akash47

    Block at rest on an inclined surface

    Homework Statement Homework Equations Component of force,equilibrium of force. The Attempt at a Solution In the problem (ii),the friction force is ##Mgcosθμ##,the component of weight in the inclined surface is ##Mgsinθ## and the component of the applied force ##F## along the inclined surface...
  38. christang_1023

    Bullet shooting vertically into a block

    Homework Statement A 28-g bullet is shot vertically into an 6-kg block. The block lifts upward 5mm (see the figure). The bullet penetrates the block and comes to rest in it in a time interval of 0.0010s. Assume the force on the bullet is constant during penetration and that air resistance is...
  39. M

    Find the mass of a block on an inclined pulley

    Homework Statement Block A is traveling down an incline plane of 35 degrees at 2m/s. It's pulling a 4kg block with a pulley and rope. Coefficient of friction is.12. How heavy must block A be ? Homework Equations F=MA F = WsinΦ + μWcosΦ mgh = 1/2 mv^2 + WD to overcome friction Vf^2 = u^2 +...
  40. Akash47

    Finding the density of a block in two layers of liquids

    Homework Statement A layer of liquid with density ##800~kg/m^3## floats on top of a volume of water. A block floats at the oil-water interface with ##3/4## of it in water and the rest of it in the liquid. What is the density of the block? Homework Equations Buoyancy =##vρg## where ##v##=...
  41. R

    Finding the mass of a block attached to a spring

    Homework Statement What is the mass of the block? Given: friction less surface, velocity at each marked point, distance between points 1 and 2, spring constant l = 7 N/m Homework Equations F=ma Kinematic equations The Attempt at a Solution I tried to solve for a in m = F/a in order to find...
  42. M

    Free body diagram on a block pushed against a ceiling

    Homework Statement A 2kg block is being pushed along a ceiling with friction by an angled force of 70 degrees. I'm asked only for the free body diagram. Homework EquationsThe Attempt at a Solution I figured both the gravitational and normal force would point downwards, but the force applied at...
  43. YMMMA

    Potential energy of a block moving up and down an incline.

    Homework Statement Which graphy represents the potential energy of the block as a function of time? Homework Equations PE=mgh The Attempt at a Solution First, the potential energy is zero until it reache the top of the incline where the potential energy is maximum. Moving down, the potential...
  44. EastWindBreaks

    Why is the output in the middle of the block diagram?

    (mentor note: not really a homework as the OP seeks understanding from an article) 1. Homework Statement I saw this on https://www.electronicshub.org/open-loop-system/, I thought the dry clothes should be the output, and heating the cloth should be the plant/process, I am so confused...
  45. M

    Conceptual Question: Block on a wedge on a frictionless surface

    Homework Statement This is more of a conceptual question, but say a block was set on top of an inclined plane, which was set on top of a frictionless level surface. Would the inclined plane move? Why or why not Homework Equations None The Attempt at a Solution My thought...
  46. J

    Forces on a Block and Friction on a Surface

    Homework Statement A 2.5 kg block is initially at rest on a horizontal surface. A horizontal force of magnitude 5.8 N and a vertical force are then applied to the block. The coefficients of friction for the block and surface are μs = 0.43 and μk = 0.24. (a) Determine the magnitude of the...
  47. sophia026

    Physics Homework -- block pressed against a wall is sliding....

    Hey! I've been trying to figure out these two problems but can't seem to get the right answer. Was wondering if someone could help me out? 1. A block is pressed against a vertical wall by a force F, as the drawing shows. This force can either push the block upward at a constant velocity or...
  48. C

    Change in the amplitude of a damped spring block oscillator

    Homework Statement A block is acted on by a spring with spring constant k and a weak friction force of constant magnitude f . The block is pulled distance x0 from equilibrium and released. It oscillates many times and eventually comes to rest. Show that the decrease of amplitude is the same...
  49. S

    Optical filter that blocks infrared and allows UV?

    Hello. I want to build camera for ultraviolet photography and reflectography. I plan to use debayer'ed backlit CMOS camera with or without Wood's ZWB3 glass UV filter. But I also need to find infrared cut filter because abudant IR radiation will ruin photos. Problem is that there are plenty of...
  50. J

    Finding the acceleration of a block of ice on a ramp

    Homework Statement A a block of ice with mass mA rests on a wedge of ice with mass mB=4.33 kg that is cut so that the surface of the wedge makes an angle of θ=38.1° with the ground. There is no friction between the pieces of ice or between the ice and the ground. At time t=0, the blocks are...
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