What is Disk: Definition and 816 Discussions

The Confederation of Revolutionary Trade Unions of Turkey (Turkish: Türkiye Devrimci İşçi Sendikaları Konfederasyonu, DİSK) is one of the four major national trade union centres in Turkey. It was founded in 1967 as a breakaway union from the Confederation of Turkish Trade Unions, and has a membership of 327,000.
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  1. E

    Solid sphere vs. disk ramp test and time difference.

    A solid sphere and a solid disk are released from rest at the top of the ramp. The inclination angle is theta to the horizontal and the vertical height of the ramp is h. Determine the time difference between the objects for them to read the bottom of the ramp. This is what I've solved...
  2. S

    What is the Mass of the Uniform Disk Used as a Cam on a Vertical Shaft?

    A uniform disk is attached at the rim to a vertical shaft and is used as a cam. The disc has a diameter of 38 cm. The moment of inertia of the disk about the axis of the shaft is 7.5*10^-3 kg*m/s. The shaft rotates uniformly about its axis at 70 rpm. The mass of the disc is closest to: a.0.12...
  3. S

    Conservation of Angular Momentum of a Disk

    A solid disk rotates at an angular velocity of 0.094 rad/s with respect to an axis perpendicular to the disk at its center. The moment of inertia of the disk is 0.12 kg·m2. From above, sand is dropped straight down onto this rotating disk, so that a thin uniform ring of sand is formed at a...
  4. A

    Rotation of a magnetic computer disk

    Hey guys, does anyone know how to approach these two problems ... can u please help me ? Question 1. A magnetic computer disk 8.0 am in diameter is initially at rest. A small dot is painted on the edge of the disk. The disk accelerates at 600 rad/s2 for ½ s, then coasts at a steady angular...
  5. B

    Circular disk rotates with student on it

    A horizontal platform in the shape of a uniform circular disk rotates on a frictionless bearing about a vertical axle through the center of the disk. The platform has a mass of 150 kg, and radius of 2.00 m. A 60kg student walks slowly from the rim of the platform toward the center. If the...
  6. B

    How Does Torque Affect Angular Momentum in a Sanding Disk?

    A sanding disk with rotational inertia 1.2E-3 kg m^2 is attached to an electric drill whose motor delivers a torque of magnitude 16 N m about the central axis of the disk. About that axis, and with the torque applied for 33 ms, (a) What is the magnitude of the angular momentum of the disk...
  7. P

    Rotational kinetic energy of a disk

    ok, so a thread with hanging mass at the end is wrapped around a disk. the disk is dropped and mass is released. how do you find the kinetic energy of the weight at a given time/distance fallen from the disk? I'm not sure to whether use rotational kinetic energy or linear kinetic energy... all...
  8. M

    How can I calculate the burst speed of a rotating disk?

    How do I determine the theoretical burst speed of a rotating disk, such as a flywheel? I went through my physics textbooks from 30 years ago with no luck. I googled, and found WAY too much information, but still no equation. Is this similar to the formula for hoop stress in a pressure...
  9. Loren Booda

    The possiblity of a solid planetary disk

    Has the existence of a planetary disk condensed as a rigid aggregate ever been postulated or observed?
  10. T

    A Bit of Byte Humor: I/O, I/O, It's off to Disk I Go!

    Hear I go *clears throat* "I/O, I/O, It's off to disk I go, to read or write a bit or byte. I/O, I/O, I/O" Came across that one today :smile:
  11. W

    Why Do Equivalent Formulas for Radial Acceleration Yield Different Results?

    Hello, I was able to solve this problem fine, but I had a question about it: "A disk 8.00 cm in radius rotates at a constant rate of 1200 rev/min about its central axis. Determine (a) its angular speed, (b) the tangential speed at a point 3.00 cm from its center, (c) the radial...
  12. S

    Solving Hard Disk Problem with Dell GX620

    I have four partitions, two of Windows and two of Linux. The Windows partitions have sizes 129 GB - C drive and 4 GB - W drive. When I check the amount of used space on C drive directly by right clicking on the C drive icon and then clicking properties, I get 55.1 GB used space and 74.1 GB...
  13. P

    Stress in a Disk: Equilibrium Relationship Explained

    Suppose I take a disk with a pie-sliced section cut out of it \] \unitlength 1mm \begin{picture}(90,90)(0,0) \linethickness{0.3mm} \multiput(20.75,77.28)(0.13,0.12){29}{\line(1,0){0.13}} \multiput(17.56,73.41)(0.12,0.14){27}{\line(0,1){0.14}}...
  14. J

    Effective Methods for Securing a Rotor Disk to a Shaft

    Hello, I am wondering what the best (and simplest) way to secure a rotor disk to a shaft is. I have a 3" diameter Acrylic disk with a 0.375" hole drilled in it to accept a 0.375" diameter steel shaft. What do you all think? Thanks, Jason O
  15. P

    Stress-Energy tensor of a rotating disk

    I'm getting a rather crazy looking result, but I'm beginning to think it may be right. Unfortunately, I haven't been able to find any specific references on the topic to check my sanity level. Basically, I'm finding that in relativistic terms, there are no pressure (or tension) terms in the...
  16. A

    Electric Charge on a uniformly charged disk

    Last question I promise,,,, A uniformly charged disk has a radius of 2.5 cm and carries a total charge of 4*10^-12C. Find the electric field on the x-axis at a distance of 20cm away. I used the equation: Ex = (sigma/ (2*Eo)) * (1 - ( 1/ sqrt( ( R^2/x^2) + 1)) this is what i...
  17. F

    Solid disk rolling up a hill problem

    I'm somewhat clueless on how to solve the following problem, since a solid disk is rolling up a hill rather than downhill. I tried using KEi + PEi = KEf + PEf, including both KEt and KEr in KEf, and I calculated that KEi = 135J (45J are KEr, and 90J are KEt). I'm not sure if I'm plugging in...
  18. J

    Finding the potential for a charged disk on a test charge

    this is my problem and it has a twist: find the electric field of a uniform disk of charge (assuming it's lying on the x, y plane) on a test charge located at the center of the disk on the z-axis but wait... here is the twist: displace the test charge a small displacement to the left. :eek...
  19. L

    Parallel Component for E over charged disk

    (NOTE: I am doing this to possibly re-enter a graduate program and earn a PhD. This is not being done for class.) DJ Griffiths, Prob. 2.6, solved. My question is about the parallel component of the \vec{E}-field. If you integrate over cylindrical coordinates, then by symmetry this component...
  20. G

    Nuclear reactions in AGN accretion disk

    As I understand it, it's all atomic material in the accretion disk of a big black hole, with very high orbital velocities and high density. However, the the disk is quite flat, and cooler than one would think with the velocities involved, because the material is swirling in smoothly, with...
  21. N

    Calculating Angular Acceleration of a Rotating Disk

    A disk with a radial line painted on it is mounted on an axle perpendicular to it and running through its center. It is initially at rest, with the line at q0 = -90°. The disk then undergoes constant angular acceleration. After accelerating for 3.1 s, the reference line has been moved part way...
  22. D

    How Does the Radius of Gyration Affect Acceleration on an Incline?

    1. A solid disc of radius r, is rolling down a variable incline (a ramp). Show that the acceleration of the centre of mass, C is given by: a=g[ sinθ – F/Ncosθ ]. I have done this as shown below. N is the normal reaction and F is friction. N = mgcosθ F = µN = µmgcosθ mgsinθ – F = ma...
  23. A

    Where Did I Go Wrong in Calculating the Moment of Inertia for a Disk?

    I am having a bit of trouble deriving the moment of inertia for a disk with uniform density: I=\int r^{2}\,dm=\int \rho r^{2}\,dV For a disk, I just used dA instead of dV. Now, to calculate the density: \rho = \frac{\text{mass}}{\text{volume}}=\frac{m}{\pi r^{2}} So now we have...
  24. A

    Inertial Disk Lab: Physics 11 H Experiment

    Ok, in my Physics 11 H class we did a lab with an inertial disk (a disk with a hub in the center, a string is attached to the hub like a huge half a yoyo where the yoyo is stationary and weights are the fingers falling down) and i need to be able to calculate the tension in the string for...
  25. U

    Troubleshooting Hard Disk Reformatting Issues

    I am trying to reformat my hdd when something weird happened. I have a P4 desktop and I wanted to reinstall everything on there. So I booted from the windows CD and it formatted and installed windows XP sp1... when the computer restarted, it said that some file was missing and it wouldn't start...
  26. Z

    How to find properties of root hard disk?

    Start Windows Explorer, right-click the computer's root hard disk, and then click Properties how do I find the computer's root hard disk in order to righ click on it?
  27. S

    Effects of Rotation on Strain in a Disk

    If a hollow disk of say radius R is heated which causes it to expand a bit and a solid disk of radius slightly greater than R is fixed inside it after which both cool down, the solid disk will be in compression and the hollow disk in tension right? Now if this disk is rotated at a some speed...
  28. S

    Rotating disk falling from string problem

    Problem Sketch Okay so this is the problem the upper disk will be of M1 mass and R1 radius both disk are solid so I(oe)=1/2MR^2 , the second disk will be HM2 , HR2. After system is left from rest I understand that the lower disc will start rotating and going down from the rope also it has...
  29. C

    Calculating Moment of Inertia of Modified Disk

    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 11.667 cm is cut out of it. The center of the hole is a distance 17.5005 cm from the center of the disk. Find the moment of inertia of the modified disk about the origin...
  30. H

    Rotational Dynamics disk of radius Question

    Please could someone check my answers to the following and advise me on any of the bits I'm stuck on. Thanks ===== Q. A disk of radius a and mass m is suspended at its centre by a vertical torsion wire which exerts a couple \fontsize{5} -c\theta on the disk when it is twisted through an...
  31. S

    Disk Scale Length Help: Troubleshooting for Science Fair

    Just a quickie I'm taking a slice of a galaxy picture and plotting luminosity vs kpc. I'm fitting a luminosity profile (de vacouleurs) and keeping disk scale length as a free parameter. However, textual values for this (referred to as h from now on) range between 3-4 kpc for most galaxies. h...
  32. J

    Uniform circular disk of radius

    Any help would be great Show that the centre of the mass of a uniform circular disk of radius, R, is at a point (4/3pi)R from the centre of the circle.
  33. C

    Faraday Disk Experiment: Testing Induction and Efficiency

    I am interested in conducting an experiment to prove or disprove the unusual qualities cited by many concerning the Faraday Disk generator. I have read from several different sources (some bias and others non bias) that an induced EMF can be measured while rotating an induction disk inside...
  34. D

    How Do You Calculate the Angular Velocity of a Disk?

    I already posted this somewhere, but silly me, i can't find it. Q: A disk of radius 2.40 cm and mass 1 kg is pulled by a string wrapped around its circumference with a constant force of 0.36 Newtons. What is the angular velocity of the disk to three decimal places after it has been turned...
  35. D

    Angular Velocity of Disk After 0.85 Revolutions

    Q: A disk of radius 2.40 cm and mass 1 kg is pulled by a string wrapped around its circumference with a constant force of 0.36 Newtons. What is the angular velocity of the disk to three decimal places after it has been turned through 0.85 of a revolution? So I started by obtaining my degrees...
  36. V

    What is the angular velocity of the disk

    So I've been using: \alpha=\tau/I More specifically: \alpha=(r*F)/(.5mr^2) I know I'm getting the acceleration just fine. I've then been using: \omega^2 = 2\alpha\Delta\Theta I know the problem is coming in here. Probably in conversion of units (rad/s^2) to (rev/s^2) or something...
  37. J

    Stopping a rotating disk with an axe

    My problem: A grindstone in the shape of a solid disk with diameter=0.480m and a mass of m=50.0kg is rotating at omega = 820rev/min. You press an ax against the rim with a normal force of F=190N View Figure , and the grindstone comes to rest in 8.00s. I need to find the coefficient of...
  38. S

    Disk speed NON UNIFORM and UNIFOR CIRCULAR MOTION

    A computer disk is 8.0cm in diameter. a refrence dot on the edge of the disk is initially located at theta= 45 degrees. The disk accelerates steadily for 1/2 second, reaching 2000 rpm, then coasts at steady angular velocity for 1/2 second. what is the speed of the refrence dot at 1...
  39. P

    When to use Washer, Shell or Disk

    I'm curious, when am I supposed to use Washer, Shell or Disk method when trying to answer questions involving integrals and volume? Is there something specific I should look out for? I just can't tell the difference. Any help is appreciated. Thanks.
  40. B

    What is the magnitude of the electric field produced by the disk

    A disk of radius 1.4 cm has a surface charge density of 4.9 µC/m2 on its upper face. What is the magnitude of the electric field produced by the disk at a point on its central axis at distance z = 12 cm from the disk? I tried solving this problem in the same way you would solve a similar...
  41. T

    EN to the parallel axis theorem.

    I have a diagram for this at http://snipurl.com/diagr There is a uniform disk with radius R, mass M, it has a string wrapped around it and is attached to a fixed rod. Part 1: Show the tension in the string is 1/3 the weight of the disk what i have done for this is Torque=Fd and...
  42. J

    Will a Western Digital 10000RPM Hard Disk Work on My PC?

    hi, a friend is heading over to malaysia in the next few days and asked me if i wanted a 10000rpm ( 8mb cache, SATA ) 74 GB WESTERN DIGITAL 10000RPM hard disk. i would say yes but i am not sure if it will work on my pc my motherboard is an ASUS P4P800SE with Intel 865PE Chipset can someone...
  43. A

    Moment of Inertia of a partial disk

    Let me first start by saying that this problem is a challenge problem and the due date has passed (friday). I've still been working on it because it stumped me. in my physics class we did some integration based inertia problems. my calculus isn't all that great so its a bit tough for me...
  44. L

    Calculating Rotational Properties of a Rotating Disk

    /k. A disk of mass 15 kg and radius 25 cm is rotating initially at 20 rad/s. A constant force of 40 N is applied tangentially to it's edge, positively accelerating the disk. a) At t= 5 seconds, calculate the- 1) rotational velocity of the disk 2) the instantaneous power supplied to...
  45. N

    Moment of Inertia and Kinetic Energy of Rotating Disk with Block

    A uniform disk of mass Mdisk = 4.4 kg and radius R = 0.28 m has a small block of mass mblock = 2.4 kg on its rim. It rotates about an axis a distance d = 0.18 m from its center intersecting the disk along the radius on which the block is situated...
  46. G

    A disk 8.0 cm in diameter is initially at rest. A small dot is painted

    A disk 8.0 cm in diameter is initially at rest. A small dot is painted on the edge of the disk. The disk accelerates at 600rad/s^2 for .5s, then coasts at a steady angular velocity for another .5s. What is the speed of the dot at t = 1 s? Through how many revolutions has it turned? I...
  47. T

    Map Cassini's oval to unit disk

    Okay, so I'm having problems figuring out how exactly i can map the interior of Cassini's oval (|z^2-a^2|<r^2 , 0<a<r) onto the unit disk (|w|<1), so that the axis of symmetry are preserved. Anyone know how to do this? :confused: (In this case, the cassini oval is a peanut shaped domain, i think)
  48. G

    Calculate Torque to Accelerate .22kg Disk to 1500rpm in 5s

    A .22kg , .22-m-diameter plastic disk is spun on an axle through its center by an electric motor. What torque must the motor supply to take the disk from 0 to 1500 rpm in 5.00 ? I used the equations T(thau)=alpha/I w_f=w_i + alpha*(t_f - t_i) I found I to be equal to .021kgm^2 then...
  49. Z

    How Can Angular Momentum Be Described for a Rotating and Translating Disk?

    Hello. Could anyone give me a hint in this problem? There´s a disk (mass m ad radius a) rotating with angular velocity w0 (only rotation). If this disk is translating in xy plane, parallel with the y-axis with its center aligned at x0, how ca I describe the angular momentum L (t), and it´s...
  50. G

    Solving a Puzzling Problem: A Disk and a Hoop

    I'm having some trouble with a conceptual problem. Your help or input would be greatly appreciated. Here's the problem. A disk and a hoop, both having the same mass, are rolled down a hill. The disk rolls faster than the hoop. Why is this so? Thank you for your time!
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