What is Disk: Definition and 817 Discussions

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DİSK is affiliated with the International Trade Union Confederation, World Federation of Trade Unions, Trade Union Advisory Committee to the OECD and the European Trade Union Confederation.

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  1. jegues

    Uniformly polarized disk on a conducting plane.

    Homework Statement A uniformly polarized dielectric disk surrounded by air is lying at a conducting plane, as shown in Fig. 2.36. The polarization vector in the disk is, \vec{P} = P\hat{k}, the disk radius is a, and the thickness d. Calculate the electric field intensity vector along disk...
  2. A

    Calculating Speed of Rotating Disks and Hoops Using Uniform Solid Disk Equations

    Homework Statement A uniform solid disk of radius R and mass M is free to rotate on a frictionless pivot through a point on its rim (see figure below). The disk is released from rest in the position shown by the copper-colored circle. (a) What is the speed of its center of mass when...
  3. P

    Diffeomorphism of a disk and a square?

    I have trouble in showing a disk and a square is not diffeomorphic. Intuitively, I know there is smoothness problem occurs at the corner of the square if I suppose there is a diffeomorphism between the two, but how can I explicitly write down the proof? I hope someone can provide me with some...
  4. N

    Calculating Hard Disk Read/Write Time & Capacity

    Homework Statement Suppose the hard disk above has 1024 cylinders, 8 tracks per cylinder, 32 sectors per track and 512 Bytes per sector. The maximum seek time is 450 msec, the time to move between adjacent cylinders is 10 msec, the rotation time is 14. a) If the entire disk was full of...
  5. D

    Question about the rotating disk

    Hey, does anyone know where I can find the correct metric for a rotating disk? Is the article at this link correct? If not, where is the error? Link to non-mainstream journal removed.
  6. N

    How much does a car's disk breaks heat up when,

    Imaging a car decelerating from 120km/h to 80km/h. How much do the disk breaks heat up if 50% of the energy translates directly as heat (to the breaks). The car's mass is 1300kg and the full mas of the disk breaks are 11kg. The disks are made of steel Q=0.46 (heat capacity) I've been using...
  7. soothsayer

    Rotating Disk Physics: SR Reconciles Fast-moving Points?

    Imagine we have a spinning disk. Points near the center of the disk rotate slowly while those increasingly far out are moving faster. Now suppose we have a sufficiently large disk such that the points on the edge of it are moving relativistically, and would classically be reaching or surpassing...
  8. perplexabot

    Electricfield of a Disk using Gauss's law

    Electricfield of a Disk using Gauss's law! Hi all. Trying to find electric field of a disk with a charge density of D and a radius R (let us assume it has a thickness h). I know you can do so by breaking up the disk into concentric rings and integrating coulombs law. However, i would like to go...
  9. C

    Finding Volume Using Disk and Washer Method: Rotation about the Y-Axis

    Consider the region bounded by the curves y=x^2+1 and y=3-x^2 a) using the disk/washer method, find the volume of the solid obtained by rotating this region about the x axis This was very straight forward v=int(1, -1) pi((3-x^2)^2)-(x^2+1)^2))dx I finished the problem with 32pi/3 which...
  10. E

    How do disk operations affect CPU utilization?

    How much is the CPU involved in disk operations. Let's say I have a long disk operation such as copying a large file for several minutes. When I look at the CPU utilization on my computer (Windows XP), it's pretty low; basically zero. So how involved in such an operation is the CPU? Does it just...
  11. A

    Is there any way to know what program has visited which disk and when?

    Call me paranoid if you will, but is there any handy tool that keep a track or can find out what program that has a possibility/ability of internet connection, has visited what directory by what time? It could be a stand alone software, could be something that comes with windows. Does anybody...
  12. D

    Laplace equation involving a disk

    Homework Statement disk has a radius C with boundary conditions V(C,\vartheta)={cos(\vartheta) ;-\pi/2\leq\vartheta\leq\pi/2. 0; otherwise solve the laplace equation Homework Equations co/2+do/2ln(r)+\sum(cn1rn+dn1r-ncos(n\vartheta)+(cn2rn+dn2r-nsin(n\vartheta) The Attempt at a...
  13. D

    Pixel pitch, Airy disk diameter and maximum aperture

    Hi, How to determine a threshold aperture, at which the diffraction begins to limit resolution of the sensor ? Which situation reflects that point: 1) Airy disk diameter / 2 = 2 x pixel pitch http://www.outbackphoto.com/dp_essentials/dp_essentials_02/essay.html" (third pixel detects the...
  14. S

    How can the vibrating disk of a speaker produce so many sounds at once

    When you listen to music, you hear the beat, the melody, and the vocals all at once... and they all emanate from the same disk. How does all the noise sound so separate and distinct from one another regardless of whether its a rumbly bass or a piercing pitch? This confusion comes from my...
  15. L

    Scan disk message appearing during start up

    Dear members, Everytime i start the system i get the following message " One of your disks needs to be checked for consistency . To skip disk checking press any key within 10 seconds" I wish that my disk needs to be checked so i didnt press any key but automatically after the specified...
  16. L

    What happens to the geometry of a spinning disk as it rotates about its center?

    If a circular disk rotates about its centre, what will happen to its geometry. Since a spinning disk has velocity gradients, different regions of the disk must contract by different proportions. For example, a uniformly moving body undergoes length contraction and its new geometry is easily...
  17. V

    Dynamics: Angular Acceleration of Rods Connected to Disk

    Homework Statement Bars BC and AB and dish OA are attached by a pin like in the picture. The dish has a constant angular velocity \omega\_{0}. Find the angular acceleration of bars BC and AB. Homework Equations Relative Motion Equations: v_{b}=v_{A}+v_{A/B}...
  18. A

    What is the Moment of Inertia of a Disk with a Hole?

    Homework Statement A uniform circular disk has radius 35 cm and mass 350 g and its center is at the origin. Then a circular hole of radius 8.75 cm is cut out of it. The center of the hole is a distance 13.125 cm from the center of the disk. Find the moment of inertia of the modified disk...
  19. L

    What is the moment of inertia of a disk with a hole about the Z-axis?

    Homework Statement A uniform circular disk has radius 39 cm and mass 350 g and its center is at the origin. Then a circular hole of radius 9.75 cm is cut out of it. The center of the hole is a distance 14.625 cm from the center of the disk. Find the moment of inertia of the modified disk about...
  20. D

    Conformal map of unit disk to itself

    Homework Statement This problem is an already solved one in Marsden and Hoffman's Basic Complex Analysis, but I can't seem to work out the last step. Here's the problem: Suppose a,b,c,d are real and ad-bc>0. Then show that T(z) = \frac{az+b}{cz+d} leaves the upper half plane invariant. Show...
  21. J

    Hard disk radial distribution function

    Hi, i am running a hard disks molecular dynamics simulation. I would like to compare the radial distribution function obtained from my simulation with the theoretical radial distribution function. May i know what is the theoretical radial distribution function? Or what data do people normally...
  22. 1

    Finding Volume Using the Disk Method

    Hi all, first time here. Huzzah! Looking for help setting up the integral for this: 1. Find the volume of the solid generated by revolving the region bounded by y = x^2 and y = 4x - x^2 around the line y = 6. 2. V = π ʃ [f(x)]^2 dx 3. I've tried every variation of: π ʃ [(x^2 - 6)^2 - (4x -...
  23. S

    What is the Proper Method for Calculating Moment of Inertia for a Disk?

    Not a homework question per se, but I'm having some issues with moments of inertia. Say I wanted to calculate the I for a ring. What I would do is: I = \int r^2dm m = \lambda L dm = \lambda dL I_{ring} = \int_{0}^{L}\lambda r^2dL And that would give the requiside mr2. My question...
  24. R

    B and H field for a long rod and a disk

    As shown in the figure attached. If both have the magnetization M, what will the B field and H fied for each object look like? why? I have no hint how to answear this question, can anyone help? any reply highly appreciated.
  25. R

    Hard Disk - Motherboard Compatibility

    I have 2 P.C.s as follows P.C.1 : 865G/GVM3-V (MS -7101 V2.0) M-ATX MicroStar Motherboard Pentium 4 Dual Core Processor 80 GB WD Hard Disk 1.5 Gb/s 512 MB DDR1 RAM 250 Watt Power Supply Bought in 2006 P.C.2 : M2N68-AM SE2 ASUS Motherboard ATHALON...
  26. P

    Finding Speed of Box and Angular Speeds of Cylinder & Disk

    In the figure, the cylinder and pulley turn without friction about stationary horizontal axies. A rope of negligible mass 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 pulley surface. The...
  27. P

    Calculating Total Charge on a Disk with Varying Charge Density

    Electric charge is distributed over a disk x^2+Y^2<=4 so that the charge density at (x,y) is o(x,y)= x+y+x^2+y^2 what is the total charge on the disk so I change to polar and get (rcos +rsin +r^2)rdrdtheta and my limits go from 0 to 2pi and 0 to 2 for my answer i got 8 pi I am...
  28. K

    Can a Rotating Conducting Disk Generate a Magnetic Field?

    In a recent homework problem for my physics class, there was a question regarding a non conducting disk with a charge, and this rotating disk (axis or rotation perpendicular to the surface, through the center) will produce a B field because of the movement of charges. Now suppose I have a...
  29. I

    Closed disk of radius limit math problem

    Homework Statement If Dr is a closed disk of radius r centered at (a,b) find lim r->0 (1/pir2) \int\intfdA over Dr. The Attempt at a Solution From mean value equality, \int\int fdA = f(x,y)A(D) where A(D) is the area of the region which here is pir2. So the lhs becomes lim r->0 f(x,y)...
  30. S

    What Is the Acceleration of a Cord Wrapped Around a Disk?

    A cord is wrapped around a homogeneous disk of radius r = 0.5 m and mass 29 kg, as shown in Fig. 2 "Cord around disk". The cord is pulled upwards with a force T of magnitude 148 N, with gravity acting vertically downwards. Determine the acceleration of the cord, in m/s2, positive if upwards...
  31. S

    How Do You Calculate the Moment of Inertia for a Disk Rotated Off-Center?

    Hi, I just got of a test that had a question about moment of inertia on it. The question "Calculate the moment of inertia of a thin uniformed disk that is being rotated about an axis of rotation". This axis is halfway between the center of the disk and the outer perimeter. The mass of the disk...
  32. D

    Eddy Current in a rotationg disk

    Homework Statement As given in the picture.The Attempt at a Solution So this is what i have done. I calculated: \frac{d\phi}{dt} = B \pi b^2 *\frac{\omega}{2\pi} = e.m.f. R = \frac{\rho a}{at} Thus, I = emf/R = \frac{ar \omega t}{\rho} Sub in I into F = BIL taking L as a. But i...
  33. E

    Angular acceleration of a computer disk drive

    Homework Statement A computer disk drive is turned on starting from rest and has constant angular acceleration. If it took 0.640s for the drive to make its second complete revolution, how long did it take to make the first complete revolution? Homework Equations...
  34. Y

    Find induced E field inside a disk in an uniform magnetic field.

    Homework Statement Uniform time varying magnetic field \vec B_{(t)} pointing at z direction, filling up a circular region on xy-plane. Find the induced E field. I tried two different ways and get two different answers. Please tell me what did I do wrong. Homework Equations Emf...
  35. B

    Calculating Revolutions with Constant Force: Solving for Angular Velocity

    Homework Statement A solid disk with a radius of 3.3cm is a rest. The disk has 1.0m of string wound on to its circumference. The string is pulled off the disk by a constant force in a time of 4.9s. How many revolutions dose the disk make while the string is being pulled off? Homework...
  36. M

    Show that the partial sums of a power series have no roots in a disk as n->infty

    Homework Statement Let f_n(z)=\sum_{k=0}^n\frac{1}{k!}z^n. Show that for sufficiently large n the polynomial f_n(z) has no roots in D_0(100), i.e. the disk of radius 100 centered at 0. Homework Equations This is a sequence of analytic functions which converges uniformly to e^z on C...
  37. S

    Tangential speed problem with a hard drive disk

    Homework Statement A computer hard drive disk with a diameter of 3.5 inches rotates at 7200 rpm. The “read head” is positioned exactly halfway from the axis of rotation to the outer edge of the disk. What is the tangential speed in m/s of a point on the disk under the read head...
  38. Telemachus

    A bar subject to a rolling disk which is released on an inclined plane

    Well, it's my second post about rigid body. I originally posted this on introductory physics, but as nobody answered this, or the previous topic, I've decided to post this here. Homework Statement I have this other exercise rigid in the plane, with which I am having problems. The rod of...
  39. Telemachus

    A bar subject to a rolling disk which is released on an inclined plane

    Homework Statement I have this other exercise rigid in the plane, with which I am having problems. The rod of mass m and length l, is released based on the vertical position of rest with the small roller end A resting on the slope. Determine the initial acceleration A. (neglect friction and...
  40. B

    Disk with constant angular acceleration

    Homework Statement A disk is under constant angular acceleration \alpha. When it starts from rest it takes 10 revolutions before it reaches angular velocity \omega. How many additional revolutions does it take to accelerate the disk further to an angular velocity of 3\omega?The Attempt at a...
  41. T

    Electric Potential of a Charged Disk

    I was working on E&M I homework with my friend, and the final question was to find the electric potential at any point on the positive x-axis of a charged disk (where the x-axis is perpendicular to the centre of the disk) We solved this easily enough, starting with a point charge and...
  42. R

    Disk brakes along the rim of the wheel?

    Disk brakes along the rim of the wheel?? Hi friends, I have a doubt. I heard that when we keep the disc brake along the rim of the wheel, less energy is required to stop the wheel. Why is it so?? Why is it not used in today's bikes?:confused:
  43. F

    How Do You Calculate the Potential on the Axis of a Uniformly Charged Disk?

    Homework Statement The potential on the axis of a uniformly charged disk at 4.7 from the disk center is 150 ; the potential 15 from the disk center is 100 . Homework Equations I have no idea what the equations are, I read my textbook looking for equations and I've been searching...
  44. H

    Electric Fields due to a charged disk.

    Homework Statement Why is this answer saying that Ea > Eb? Homework Equations Everything pertinent to this question is located in this picture: http://img94.imageshack.us/img94/1187/ch22q9part1.png [PLAIN]http://img94.imageshack.us/img94/1187/ch22q9part1.png The question is...
  45. J

    Friction and Rolling of a disk

    Homework Statement Disk a and b are identical and roll across a floor with equal speeds. Disk a rolls up an incline, reaching a max height h, and disk B moves up an incline that is identical except that it is frctionless. Is the max height reached by disk b greater than, less than, or equal to...
  46. Q

    Total luminosity of a galactic disk

    This is basically problem 2.8 from Sparke & Gallagher "Galaxies in the universe". There's only one area I'm having trouble with. I've solved the surface density for stars in the galactic disk (# stars per unit area) as \Sigma(R)=2\exp(\frac{-R}{h_R})h_R Now, with L_0 being the...
  47. S

    Complex Analysis - Proving a bijection on a closed disk

    Homework Statement For each w \in \mathbb{C} define the function \phi_w on the open set \mathbb{C}\backslash \{\bar{w}^{-1}\} by \phi_w (z) = \frac{w - z}{1 - \bar{w}z}, for z \in \mathbb{C}\backslash \{\bar{w}^{-1}\} \back. Prove that \phi_w : \bar{D} \mapsto \bar{D} is a...
  48. R

    Finding B and H at Center of Disk: Linear Magnetic Material

    Homework Statement A linear magnetic material in the shape of a circular disk of radius R and thickness d (d<<R) has a uniform magnetization M parallel to its axis. Find B and H at the center of the disk Homework Equations The Attempt at a Solution As the magnetization is uniform...
  49. K

    Rotational Inertia of Irregular Disk

    Homework Statement an irregularly shaped plastic plate with uniform thickness and density (mass per unit volume) is to be rotated around an axle that is perpendicular to the plate face and through point O. The rotational inertia of the plate about that axle is measured with the following...
  50. M

    What is the Angular Speed of a Disk Pulled with a Constant Force?

    Homework Statement A 6kg disk with radius 0.3m initially not spinning. String is wrapped around disk, you pull with constant force of 25N through a distance of 0.6m. What is its angular speed. Homework Equations Krotational=1/2 I w2 The Attempt at a Solution I can't seem to...
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