What is Rotating disk: Definition and 87 Discussions

The Rotating disk viscometer, or "Mooney Machine" as it is sometimes referred to in the rubber industry, is the standard viscometer for measuring material viscosity and scorch time for rubber before vulcanization. It was developed in the 1930s by Melvin Mooney. For a specific temperature, scorch time describes how long it will take the material to vulcanize. For example, a scorch time at ambient temperature indicates the rubber will be able to remain unvulcanized at room temperature for an extended period of time.

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  1. N

    Motion of a ball along a groove on a rotating disk

    Will a ball placed tightly (radius of ball=width of groove) in a groove(length of grove along radius) on a rotating disk have any motion along the groove. The frictional force is zero.
  2. C

    A rotating disk with two attached masses that slide without friction

    Homework Statement A disk rotates with angular velocity w. Two masses, Ma and Mb, slide without friction in a groove passing through the cnter of the disk. They are connected by a light string of length L, and are initially held in position by a catch, with mass Ma at distance Ra from the...
  3. 5

    Calculating Friction Force on a Rotating Disk

    Homework Statement The thing that is lying on the disk(Disko), is rotating together with disko. After the rotary frequency of disko grew twice (N X 2), friction(rubbing) Force grew F=6 ( F + 6). You have to understand friction Force module at the original frequency. Homework Equations...
  4. B

    SR, Doppler effect on rotating disk

    Homework Statement taken directly from Rindler A large disc rotates at uniform angular velocity ω in inertial frame S. Two observers O1 and O2 ride on the disc at radial distances r1 and r2. They carry clocks C1 and C2 they adjust to keep with clocks time with S, i.e., they have been adjusted...
  5. P

    What is the velocity of the mass in the lab's frame of reference?

    Hi, Homework Statement A horizontal smooth disk of radius R rotates around its axis with constant speed ω. At t=0 a mass m is thrown at speed v0 (in the lab's frame of reference) towards the center of the disk. I am asked to write down the velocity vector of the mass in the lab's frame of...
  6. A

    Trying to find the Tensile Pressure in a Rotating Disk

    OK, so I'm trying to build a hyper-fast rotating disk, probably of aluminum. The tensile strength is about 200MPa (note that this is a pressure, which makes sense), and I'm trying to calculate the tensile pressure throughout the disk. The point being to find out how fast I can spin the thing...
  7. L

    Fields generated by a rotating disk

    Homework Statement We have an uniformly charged disk with total charge q, which is rotating around its axis with constant angular velocity w. Calculate electric and magnetic field in the axis and in the rotation plane. Calculate the radiated power in one cicle. Homework Equations...
  8. Q

    3D Rigid body dynamics - Rod over rotating disk

    Homework Statement A thin uniform rod is attached to an axis through its midpoint. The axis is standing on a disk rotating with constant angular speed \Omega about its symmetry axis. The rod's midpoint is located directly above the rotational axis of the disk. Let \theta denote the rod's...
  9. N

    What determines the speed of two balls on a rotating disk?

    Homework Statement Homework Equations I=mr^{2} L=ωI ω=\frac{L}{I} The Attempt at a Solution I thought that since the moment of inertia was larger for the ball on the outside its angular speed would be slower. So then it would take longer to hit the wall.
  10. X

    Calculating Average Tangential Stress for Non-Uniform Rotating Disk

    Assumed a disk loaded with external pressure Po, internal Pressure Pi and rotating at the speed ω. I'm sure that average tangential stress for uniform thickness rotating disk can be calculated using equation below : σ avg = (PiRi/Ro-Ri) - (PoRo/Ro-Ri) + (ρω^2) / 3(Ro^2+RoRi+Ri^2) Ro = outer...
  11. 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.
  12. 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...
  13. K

    Torque friction on a rotating disk

    A uniform horizontal disk of mass M and radius R is rotating about its vertical axis with an angular velocity \omega. When it is placed on a horizontal surface, the coefficient of kinetic friction between the disk and the surface is \mu_k.Find a)the torque \tau exerted by the force of friction...
  14. L

    Dynamics rotating disk, solve for r and theta magnitudes

    Homework Statement A screen clipping of the problem is here: http://img529.imageshack.us/img529/1738/dynamicsquestion2.jpg We have a circular disk that roates about its center, 0, with a constant angular velocity \omega (\omega = \dot{\theta}. The disk carries two spring-loaded plungers...
  15. A

    Velocity and Acceleration on a Rotating Disk?

    Homework Statement If you are standing on a rotating disk which is rotating at a constant angular velocity and you walk with a speed v along a straight radial line, then what are you velocity and acceleration? Homework Equations The Attempt at a Solution I just wanted to check if...
  16. F

    The mystery of the tangent and the radius fluid in spiral pipe on rotating disk

    Here's something simple but also a bit puzzling, let me know if you have any ideas... For clarity, I'll describe three cases before asking the final question (skip ahead if you like). 1. Mounted on a disk are two curved fences, just a few centimetres apart from each other. Between the fences...
  17. T

    Magnetic field above rotating disk

    Homework Statement What is the magnetic field a distance z above a rotating disk (ang.velocity w) with surface charge density inversely proportional to the square of the distance from the centre of the disk. Homework Equations K = v*surface charge density B = (constant)*integral of...
  18. D

    Rotating Disk angular momentum

    I need some help with this problem. Any help would be greatly appreciated. It is due tonight. http://session.masteringphysics.com/problemAsset/1035644/7/knight_Figure_13_47.jpg Use the link above to solve the problem. Part 1) What is the magnitude of the angular momentum of the 3.1 kg...
  19. R

    Need help analyzing the failure of a rotating disk

    Homework Statement hi, i'm working on a project for a materials class. we chose to analyze a spacer in a jet engine that catastrophically failed. The spacer failed initially due to rubbing between it and a vane case on the outer most radius of the spacer. We're not analyzing the vane case...
  20. B

    Is It Zero? Tangential and Centripetal Acceleration on a Rotating Disk

    rotating disk short question! Homework Statement If object is rotating on a disk with a constant angular speed, which of the following is zero? the object's tangential acceleration the object's centripetal acceleration both (a) and (b) are zero niether (a) or (b) are zero...
  21. F

    Rotating disk with friction on the boundary

    Hi everybody! I'm having some problem with the following system... I have a 2D problem, a disk is rotating with constant velocity, but there is a friction on the boundary due to the contact between the disk and the surrounding material. I'd like to find the analytical formula of the...
  22. K

    Torque about the axle of a rotating disk

    Homework Statement "The 19.8 cm diameter disk rotates on an axle through its center. F1=18.1 N, F2=26.6 N, F3=26.6 N, F4=18.1 N, and d=4.64 cm. What is the net torque about the axle? " http://i4.photobucket.com/albums/y111/kathy_felldown/kn-pic1314.png I have two questions about this...
  23. A

    Faradays rotating disk paradox

    Hello, I was reading about Faradays rotating disk paradox wherein when both the copper disk and magnet are rotated together an eddy current is induced along the radius of the copper disk. My question is if a maganitized steel disk (with one side being the N pole and the other side...
  24. N

    Angular Momentum: Rod on Rotating Disk

    Homework Statement A uniform disk (like a record turntable) turns with a frequency of 5.2 rev/s around a frictionless spindle. A non-rotating rod of the same mass as the disk and length equal to the disk's diameter is placed on the freely spinning disk so both turn around the spindle. (Idisk...
  25. M

    Angular Speed of Rotating Disk: Omega Final & Initial

    Homework Statement A uniform disk is set into rotation with an initial angular speed about its axis through its center. While still rotating at this speed, the disk is placed in contact with a horizontal surface and released. What is the angular speed of the disk once pure rolling takes place...
  26. D

    Physics Rotating Disk, Moment of Inertia, Angular Momentum, Angular Velocity

    Homework Statement Here's the problem statement, uploaded onto google docs: http://docs.google.com/View?docid=d277r7r_48f97jqsgs Homework Equations The Attempt at a Solution i) L=r*p L=R*m*v I think that's the answer, b/c they don't give us any constants to work with, but...
  27. S

    Rotating Disk Homework: Calculating Angular Acceleration and Time

    Homework Statement A disk rotates about its central axis starting from rest and accelerates with constant angular acceleration. At one time it is rotating at 7.0 rev/s; 83 revolutions later, its angular speed is 18 rev/s. Calculate (a) the angular acceleration (rev/s^2), (b) the time required...
  28. A

    Angular momentum of a rotating disk

    Homework Statement What is the angular momentum of the 1.2kg, 3.6cm diameter rotating disk in the figure below? http://i241.photobucket.com/albums/ff4/alg5045/ex13-47.gif Homework Equations The Attempt at a Solution I tried using L = Iw. w = 600 rev/min x (1 min/60s) x 2*pi...
  29. J

    The Ehrenfest Rotating Disk Paradox: Exploring Circumference in a Lab Frame

    I read the entry about the Ehrenfest rotating disk paradox on Wikipedia, but the entry does not actually answer my question about what happens to the circumference of the disk in the "resolution of the paradox" section. All I want to know is what happens to the circumference of the rotating...
  30. M

    Calculating Torque for Rotating Disk on Flat Surface

    Ive been trying to find formulas that help describe the torque needed to rotate a flat disk on a flat surface when the coefficient of friction between the 2 materials is known. The first surface is a glass window (so a vertical plane) the second surface is a rotating disk of wet sponge...
  31. 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...
  32. 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...
  33. 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...
  34. 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...
  35. 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...
  36. 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...
  37. 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...
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