Disk Definition and 819 Threads

Homework Statement A thin conducting disc has radius a thickness b and electrical resistivity ρ. It is placed in a uniform time-dependent magnetic induction ##B = B_0 sin ωt## directed parallel to the axis of the disc. Assuming that ρ is large, find E at a distance r < a from the axis of the...

Homework Statement Homework EquationsThe Attempt at a Solution O is the center of the disk Part a) The emf induced across PS can be found by thinking as if a rod PS is rotating and translating . The component of velocity of rod perpendicular to its length is vsin45° = v/√2 . The length PS...

How can I find the electrostatic potential of any point on a charged disk with radius R and surface charge density σ

I am studying topology right now and am a bit confused about the idea of triangulation. The definition is: if a topological space X is homeomorphic to a polyhedron K (union of simplexes) then X is triangulable and K is a (not necessarily unique) triangulation. Apparently ## K_0 \equiv {1} \cup...

So looking at pictures of dwarf galaxies and how they're just an irregular (pun intended) mess and they do not have the disk shape that we, ironically, associate with galaxies despite a small minority of galaxies being big enough to have and maintain their disk shape. Like apparently the...

Homework Statement We place a rubber on the edge of a rotating disk. What forces act on the rubber? At what angular velocity, why and in what direction will the rubber fly off the disk? Homework Equations http://images.tutorvista.com/cms/formulaimages/83/angular-speed-formula111.PNG The...

Homework Statement [/B] Homework Equations r[/B]BA= rA-rB UBA= rBA/rBAF= KS F= Magnitude of force S=Spring deformation >Lf-LiThe Attempt at a Solution So far I have found the components for RB and some RA, but the thing I'm missing is the R AZ. I know that at 0 and 90 degree the spring is...

Homework Statement A wheel consists of a circular uniform disk with a circular hole in it. The disc is of radius R and mass per unit area ρ. The hole is of radius ro and an axle of radius ro passes through it. The centre of the hole is offset radially from the centre of the disk by ro. The...

Homework Statement 2. Equations v=q/4πrε 3. Attempt at solution Can I find the total charge by integrating the charge density equation from 0 to 2π and then plug that into the above equation?

Homework Statement Take the expression 21.11 (pictured below, specifically the bottom one) for the electric field above the center of a uniformly charged disk with radius R and surface charge density σ, and show that when one is very far from the disk, the field decreases with the same square...

Homework Statement how far from the rim of a disk of Radius R must the pivot point be located in order for its period of oscillation to be a minmum where R is the distance from the point to the centre of mass? I'm stuck at the derivative because I saw a similar problem where the answer is...

Homework Statement A crucial part of a piece of machinery starts as a flat uniform cylindrical disk of radius R0 and mass M. It then has a circular hole of radius R1 drilled into it. The hole's center is a distance h from the center of the disk. Find the moment of inertia of this disk (with...

Does this neutron star have an accretion disk?: https://en.wikipedia.org/wiki/IGR_J11014-6103#/media/File:Lighthouse_nebula.jpg

Homework Statement I won't be following this format exactly, but I'm trying to come up with an idea for a physics exploration I need to do and I think I'm finally getting close to something. I'm trying to figure out what actual experiments I can do with this topic, and if they're of a high...

Homework Statement Hoping to outdo his physics professor, Doofus wants to dramatically demonstrate parabolic motion by throwing a cheese wheel of massm and radius r off of the top of the UW observatory, which is at a height 3R above the roof of the physics building, as shown in the diagram...

I know that the angular momentum is conserved in the below example, but intuitively I am struggling. Anyway, here goes! Homework Statement A bullet that is traveling without spinning hits and sticks into a filled disk tilted on its side an arbitrary distance "d" away from the center of mass...

A string is wrapped around a uniform disk of mass M = 1.3 kg and radius R = 0.05 m. (Recall that the moment of inertia of a uniform disk is (1/2)MR2.) Attached to the disk are four low-mass rods of radius b = 0.08 m, each with a small mass m = 0.3 kg at the end. The device is initially at rest...

Just curious, explanation if youre going to answer please! 2 horizontal disks stacked on one another spinning at constant v, (about a frictionless axis perpendicular to their center), both have mass. Okay, so let's say its possible to instantaneously remove the top disk. So would that make...

Find the coordinate of center of mass. Given: The quarter disk in the first quadrant bounded by x^2+y^2=4 I tried to solve this problem but can't figure out how to do it. so y integration limit is: 0 <= y <= sqrt(4-x^2)) x limit of integration: 0 <= x <= 2 and then after the dy integral I...

1. A solid disk of radius R and mass M is initially spinning clockwise with an angular velocity magnitude ω. It is placed against a flat, horizontal surface with a coefficient of kinetic friction of μ. Find the frictional torque magnitude on the disk, and how long it will take the disk to come...

Homework Statement Describe the motion of a gyroscope with center of mass fixed on a rotating disk in coordinates of an observer which is at rest on the disk in the absence of gravity. Homework Equations The hint given was to somehow use Fermi transport, so I'm guessing: \mathbb F_u X=\nabla_u...

So I'm getting ready for an exam on tuesday, and I'm using each method for volumes of revolutions for every problem but I'm not getting the same answers. So, let's use this as an example: y = 5x; the shaded region is from [1,2] Using the disk method (about the x-axis) I find: R(x) = 5x; r(x)...

The following picture has been posted in the Astronomy section (by Dave C426913). https://www.physicsforums.com/file:///C:/Users/John/AppData/Local/Temp/msohtml1/01/clip_image001.jpg Source: http://www.space.com/4643-incredible-comet-bigger-sun.html Why does the comet fluctuate in size but...

Hi, I've been struggling on this homework problem for quite a few hours now and would really appreciate a pointing in the right direction. It's a fairly entertaining problem that I'm getting stuck on in several places. 1. Homework Statement The problem goes: "An erratic engineer, who lives in...

A uniformly charged disk has radius R. It was a charge density and is located above the conducting plane at a distance a. The disk is parallel to the conducting plane. Find the electrostatic potential at (0,0,z) in the region above the plane. The conducting plane is grounded

Homework Statement A disk of radius R carries a uniform surface charge density σ. (a) Using the results for the uniformly charged ring given in the lectures, or otherwise, compute the infinitesimal electric field dE due to the circular slice the disk of charge dQ shown in the figure. Express...

Homework Statement The disk in Figure 3.30 of radius R rolls without slipping with constant angular velocity Ω. Carved inside the disk is a slot and a mass moves inside the slot. Denoting the position of the mass inside the slot by s, calculate the velocity and acceleration of the mass as a...

Homework Statement Homework EquationsThe Attempt at a Solution I think if I can locate the instantaneous axis of rotation ,then may be motion/velocity of CM could be determined . In the attached figure I have marked the two points A and B which are instantaneously at rest .The black arrows...

Hi I am having a difficulty understanding how to write the circuit equation inside a disk which rotates in magnetic field. the disk is made of conductor material. the resistance of the disk is: r the answer is: ir=emf+v(a)-v(b) if someone could explain it would be great! and how do i know where...

Homework Statement Suppose you have a disk of radius r at x=y=z=0 with its normal pointing up along the z-axis. The disk radiates with specific intensity I(\theta) from its upper surface. Imagine the observer plane is at z=Z, where Z is much greater than r. Let I(\theta) = I = constant...

Homework Statement https://courses.edx.org/asset-v1:MITx+8.MechCx_2+2T2015+type@asset+block/rolling_quiz_3.svg A block of mass mb and a disk of mass md and radius r are placed on a symmetric triangular slope connected with a massless string over a massless pulley as shown above. The string is...

Homework Statement The disk of mass m and radius R is at position (a), upwards. it is free to rotate round point O on it's circumference. If falls and reaches state (b), horizontal position. What are the velocities and accelerations in position (b) Homework Equations Moment of inertia of a...

Why isn't the Oort Cloud shaped like a disk like the asteroid belts and how the planets orbit? Also, why exactly do the planets orbit in that flat disk shape?

Homework Statement Faraday's disk with radius of axle r1 and radius of disc r2 is shown in the picture below. Disc rotates in the homogenous magnetic field whose vector B is vertical to the disc. If disc is spinning 1000 rpm find induced voltage between r1 and r2 and what is maximal value of...

Homework Statement I'm reading Griffith-Introduction to electrodynamics, In chapter 2 about electrostatics, I've encounter few problems that I've managed, to solve (luck !), I'm asked to calculate the electric field due to a charged disk of radius R in a point P above the center (Pic) Homework...

Hi! I am new to ANSYS and I am trying to understand a simulation done by some one else. I have a disk with a spiral in it, and it looks like there is a remote force being applied at the centre of the disk, but spread over the entire face. I don't understand how this force is being spread...

Homework Statement A disk of radius R and mass m rotates on a floor with coefficient of friction μ and makes a circle of radius r0 at constant speed v0. What is the friction force between the disk and the floor. What's the inclination angle α to the vertical. It's suggested in the question to...

Homework Statement What is the angular inertia of a disk (cylinder) with... Maximal radius, rmax = 10cm Thickness, h = 4cm density, d = 3g/cm3 rotational axis in its centre (like the axis of clock hand in a disk shaped clock) Please show and explain your procedure in finding the...

Homework Statement (Important disclaimer: I came up with this problem out of curiosity in a classical mechanics course, so it might not be in a textbook, in the right place, or even solvable for that matter. However, I feel like it should be solvable, and most likely with elementary methods...

Homework Statement Two identical disks with mass m and radius r are connected via a massless wire of length L which is winded up around both disks. Disk B is connected to the ceiling and is free to rotate around its axis. Disk A is besides disk B and will fall due to the gravitational force...

Homework Statement A disk of mass M and radius R is help up by a massless string. Let there now be friction between the disk and the string, with coefficient u. What is the smallest possible tension in the string at its lowest point? The problem is problem 8 from here...

Is the no. of electrons on a brand new unused and untested harddisk is different from no. of electrons on a used hard disk completely filled with data. i mean will there be even a change of one electron? Please consider the following points before answering: 1- Does all the electrons from a...

Homework Statement Hey y'all. Heres the problem: The flywheel to the right is spinning at 300 radians per second in a counter clockwise direction. The brake (to the left) is applied with a force F of 5kN. How long will it take the flywheel to stop rotating? Assume:  The flywheel is made of...

i can not seem to figure out how is the magnetic flux is changing and thus the current is induced , "A "is constant (same disk is spinning ) and "B" is constant and does not change , so how is the current induced ? and more specifically how is the change of magnetic flux is happening ? thanks...

Homework Statement A lamina has constant density \rho and takes the shape of a disk with center the origin and radius R. Use Newton's Law of Gravitation to show that the magnitude of the force of attraction that the lamina exerts on a body of mass m located at the point (0,0,d) on the positive...

We have built a cold gas cannon that utilizes burst disks as the means to quickly release the built up pressure with maximum flow. The bore for the burst disk is 2" and the material is Brass 260 H02 (1/2 Hard). The disks are solid and flat (i.e. no scoring or features to promote a certain type...

Homework Statement Hi all, I just had a quick question regarding a problem that I have to write a lab report on. The problem involves solving for the moment of inertia of a system that involves a pulley with a hanging mass attached to a spool that turns a flywheel. The solution is supposed to...

< Mentor Note -- thread moved to HH from the technical engineering forums, so no HH Template is shown > A rod rolls without creep. And the disk rolls without creep on Q. The rod can just moves on y. Which is the relation among Va and Vohm? Va= velocity in A My resolution: in Q we know that...

Homework Statement Homework Equations Read below The Attempt at a Solution A) D. As the mass of the students gets further away from the axis of rotation, the rate slows down (remember the skater with arms out). B) T. No explanation currently... C) ? D) T. The students exert a force on...

Homework Statement A ball of mass m is thrown with a velocity v at a disk of mass M which sticks to the rim on impact.https://s3.lite.msu.edu/res/msu/perl_author/P3_PRELECTURE/L_CONSERVATION/IMAGES/CQ1.png For the system of the ball and disk, what is the total initial angular momentum about...