Disk Definition and 783 Threads

Homework Statement A uniform solid disk of radius 7.1m and mass 30.3kg is free to rotate on a fricionless pivot through a point on its rim. [picture: http://www.wellesley.edu/Physics/phyllisflemingphysics/107_p_angular_images/figure_9.gif] If the disk is released from rest in the position...

Is there a strength and/or field density difference between ring and disk magnets? I want to know which would create stronger eddy currents when dropped through a copper tube (which one would fall slower).

Homework Statement The 20-cm-diameter disk in the figure can rotate on an axle through its center. What is the net torque about the axle? image: http://session.masteringphysics.com/problemAsset/1000963/5/knight_Figure_13_14.jpg Homework Equations τ=Frsinφ The Attempt at a...

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...

A woman with a mass of 45.0 kg is standing on the rim of a large disk that is rotating at an angular velocity of 0.490 rev/s about an axis through its center. The disk has a mass of 120 kg and a radius of 4.50 m. Calculate the magnitude of the total angular momentum of the woman-plus-disk...

A flat uniform circular disk (radius = 4.69 m, mass = 280 kg) is initially stationary. The disk is free to rotate in the horizontal plane about a frictionless axis perpendicular to the center of the disk. A 55.0-kg person, standing 1.59 m from the axis, begins to run on the disk in a circular...

A flat uniform circular disk (radius = 4.69 m, mass = 280 kg) is initially stationary. The disk is free to rotate in the horizontal plane about a frictionless axis perpendicular to the center of the disk. A 55.0-kg person, standing 1.59 m from the axis, begins to run on the disk in a circular...

Hi! What do you know about Saturn's Nord Pole hexagon? Is sure than the Saturn's hexagon is owed to nothing else but his convection. Then we ask ourselves what fact makes the convection from the Saturn's North Pole. There are two possibilities: 1). the convection is due to a temperature...

Suppose a solid disk of radius R is given an angular speed about an axis through its center and then lowered to a horizontal surface and released, the coefficient of friction between disk and surface is u. What is the distance traveled before pure rolling occurs? Conservation of Momentum...

Homework Statement A disk with width b and radius a. An element of resistance is: dR=\rho \frac{2\pi r}{bdr} How do I integrate this? Thanks in advance. :approve: Homework Equations The Attempt at a Solution

Homework Statement A flat uniform circular disk (radius = 2.50 m, mass = 1.00 102 kg) is initially stationary. The disk is free to rotate in the horizontal plane about a frictionless axis perpendicular to the center of the disk. A 55.0 kg person, standing 1.55 m from the axis, begins to run...

Homework Statement 2. a) Find the potential due to a continuous charge distribution of a disk with a surface charge, x, at point P. b) Find the electric field for part A using: attached formula . Diagram attached. Homework Equations attached. The Attempt at a Solution Well my...

A cylindrical disk has volume 8.99 × 10-3 m3 and mass 8.07 kg. The disk is floating on the surface of some water with its flat surfaces horizontal. The area of each flat surface is 0.633m2. (a) What is the specific gravity of the disk? (b) How far below the water level is its bottom surface? (c)...

I have not attempted to work on these, the only attempt I've done was look and stare at the questions and not know where to start or even begin the problem. I do not know which formula to use either. given is highlighted in bold lettering. Unfortunately i have other homework and these problems...

Homework Statement A uniform solid disk of radius (r) 6.71 m and mass (m) 38 kg is free to rotate on a frictionless pivot through a point on its rim. If facing the disk, the pivot is on the left side. The disk is then released. What is the speed of the center of mass when the disk reaches a...

Homework Statement A thin disk with a circular hole at its center, called an annulus, has inner radius R1 and outer radius R2. The disk has a uniform positive surface charge density omega on its surface. Figure's link...

Homework Statement (See the attachment) A thin string has been wound around a homogeneuos circular disk A in such a way that the disk can roll on a horizontal surface. The mass of the disk is M, and has radius R. The string goes around a small frictionless pulley C at a height 2R above te...

I was wondering about something. Say you had a really large disk, impossibly huge, and you span it around. Presumably you could only spin it so fast that the edge of the disk cannot be spinning faster than the speed of light. But why? What stops you from spinning it just a little bit faster?

Homework Statement A stationary uniform-density disk of radius 0.8m is mounted in the vertical plane. The axle is held up by supports that are not shown and is frictionless. The disk has a mass of 3.6 kg. A lump of clay with mass 0.3 kg falls and sticks to the outer edge at <-0.48, 0.64...

Homework Statement Suppose a disk of radius 'r' is rotation on a surface. If the center G moves a distance 'd', then what is the distance traveled by a point on the top of the disk (on its edge or circumference). Homework Equations theta = s / r ; where theta is the rotation in rad, s is...

Diameter of disk? Question: Consider a flywheel made of iron, with a density of 7800 , in the shape of a uniform disk with a thickness of 12.4 . What would the diameter of such a disk need to be if it is to store an amount of kinetic energy of 14.6 when spinning at an angular velocity of 91.0...

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...

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...

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...

[FONT="Times New Roman"][SIZE="2"] [SIZE="4"]Hey guys, does anyone know how to approach these two problems ... can u please help me ? [SIZE="3"]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...

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...

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...

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...

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...

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

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...

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...

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}}...

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

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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?

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...

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...

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...

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...

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...