Disc Definition and 374 Threads

Hi, I live in 6th floor of an apartment. To prevent birds from pooping beside my window, I hang some unlabeled CDs along a string outside the window. The window is facing east, and people start complaining about it, that it might cause fire. I wonder if that is even possible? I personally do...

http://www.maths.qmul.ac.uk/~rpn/ASTM735/lecture3.pdf The diagram on page 26 is the accretion disc. The torque acting on the inner edge of the ring (the one that has a thickness of dR in the diagram) is RFin = -2\piR3\nuƩ\frac{dΩ}{dR} The torque acting on the outer edge of the...

The Poisson Integral Formula is a representation of the bounded solution of the Dirichlet problem for Laplace's equation in the interior of the disc. Derive the corresponding formula for the Dirichlet problem in the exterior of the disc, again assuming that the solution is bounded.So we derived...

Analytic in the unit disc $z^7$ yes $|z|$ no $\frac{1}{z}$ yes Correct?

Homework Statement The system is made of a disc the center of which is pinned to the origin (so the disc cannot translate), and some weights that can be stuck on the disc to make it tilt (weights do not translate on the disc) (see images attached). There is no friction whatsoever. The only...

The system is made of a disc the center of which is pinned to the origin (so the disc cannot translate), and some weights that can be stuck on the disc to make it tilt (weights do not translate on the disc) (see images attached). There is no friction whatsoever. The only force is gravitational...

Homework Statement The problem: There is an illustration and the question is to find the force F to lift a concrete block gate if the the concrete weighs 160 lb/ft3. The block is 3' in diameter and 1' thick. It is in a tank of fresh water 15 ft down. the specific weight of the fresh water...

This is regarding an accretion disc orbiting a star. In the z (vertical) direction there is a hydrostatic equilibrium. \frac{1}{ρ}\frac{∂P}{∂z} = -\frac{GMz}{(R^{2} + z^{2})^{3/2}} The right hand side of the expression is the Gravitational potential energy and the left side is the pressure...

Now the function f is holomorphic in an open disc U and that Re( f ) is constant in U. I'm trying to show that 1)f must be constant in U. 2) the essential property of the disc U that it used here 3) an example of an open set U for which the conclusion fails. Let f=u+vi where u is a...

Homework Statement Suppose that f is holomorphic in an open disc U and that Re(f) is constant in U. I have to show that f must be constant in U. Also what is the essential property of the disc U that it used here? Give an example of an open set U for which the conclusion fails.Homework...

Homework Statement A circular disk with a rectangular hole has a radius of 0.600 m and mass of 0.390 kg. It is suspended by a point on its perimeter as shown in the figure. The moment of inertia about this point is I_p = 2.60E-1 kgm2. Its center of mass is located at a distance of s=0.120 m...

In an induction meter two coils induce two eddy currents in same disc.It is said that the disc rotates due to the torque produced by the interaction of these currents with each other.How is that?I don't know the governing law.Can the torque be derived from the basic maxwell's equation?

The TMC channel is showing "Close Encounters of the Third Kind" which brings back the memory of RCAs Capacitance Electronic Disc. Anyone remember these? http://upload.wikimedia.org/wikipedia/en/thumb/e/ed/Ced_cart2.jpg/670px-Ced_cart2.jpg The first "video disk" I ever purchased/watched was:

Homework Statement In the disc brakes that slow down a car, a pair of brake pads squeezes a spinning rotor; friction between the pads and the rotor provides the torque that slows down the car. If the normal force that each pad exerts on a rotor is 85 N, and the coefficient of friction is 0.62...

Hi, how to calculate the limit of load you can place on the top of the circular plate with a quite big circular hole in it (OD 10 cm, ID 5 cm)? the question is how to calculate the thickness needed to bear 1 kg which is spread on the whole area (1 kg heavy object with the same shape as the...

Homework Statement mass of the mouse = 0.05 kg disc's radius = 0.2m disc's angular speed = 33 rev / min assume that the angular speed ω doesn't change Homework Equations tangential speed = ω * r The Attempt at a Solution well, what i did was: drew the vectors, one was the...

Household physics question: Before I left town for 3 weeks the lock on my apartment door was loose in its encasement. I had to hold it in place while turning the key or the inner disc would rotate uselessly inside the outer ring: http://scott-shepherd.com/share/forums/lock.jpg When I came...

Homework Statement Its actually not a homework , i am just curious about this I have disc with a hole in middle , R1 is inner radius , R2 is outer radius , Mass M is the disc's mass . Let density of disc uniform . I did it this way . - λ.dA=dm λ.pie.r.dr=dm as Area=pie.r^2...

Homework Statement Essentially, I am trying to determine the force that must be applied to a rotating disc to that stop that disc from rotating in a certain time period. The disc is rotating at 5800 rpm, the disc has a radius of 5 inches, and a thickness of 0.087 inches. The disk is made...

Homework Statement As said in the title, why is the thick disc of our galaxy hard to study? The attempt at a solution I thought at first it may have something to do with the fact that the thin disc is so populated with stars that the light coming from it may interfere when trying to...

Hi guys, I am really stumped by this 1st yr Dynamics question, and would appreciate any help on how to approach the question. Homework Statement Homework Equations Torque equations and Force equations Moment of inertia for disc rotating around centre: (mr^2)/2 After using parallel...

Homework Statement The electric field, E a distance z above a circular loop of charge density lambda, radius r, in the x-y plane centred on the origin, is given by E(z)=[lambda z r] i(subscript z)/[2 epsilon0((z^2 + r^2)^(3/2))] a) using this, find the electric field, E, a distance z...

Homework Statement A thin disk of radius R consists of a uniformly distributed total charge Q. The disk lies a distance D above a grounded perfectly conducting plane. The disk and the plane are parallel. Set the conducting plane in the x-y axis, and the z axis through the center of the disk...

Hi, I have an annular disc that looks like the following: I need to get the elasticity of the material, since I don't have any information on it. Does anyone have any suggestions on how I can calculate the elasticity? Maybe I can get a force/displacement curve by bending the disc...

Hi all... my first time here... I hope someone can help. I'm toying with a home project (in the early conceptual stage), and the attached picture shows "in general terms" what I'm trying to figure out. The outer 'wheel' rotates about its central axis, driven at that axis by a small motor...

Homework Statement calculate the gravity acceleration at an arbitrary location due to a disc of thickness h, radius r and density p Homework Equations g=Gm/r^2 The Attempt at a Solution define r in terms of the vector magnitude from the measurement point to some point on the...

Homework Statement the e field is given by (2*pi*k*omega)[1-(1+(R^2)/(z^2))^-.5] I was wondering if the capital R in that equation is the radius of the charged disk? And if so, why is it capitalized?

Hi, Like a lot of people programming, I created a simplistic 2D collision engine. This engine handles the collisions of circles (I know I typed "disc" in the title, but I wanted to avoid replies like "circles don't really exist so they can't collide".) The simulation is friction-less, so...

How does the angular velocity change with increase in the mass? For example : if there is a shaft rotating at 1500 Rpm , then if a disc of 5 kg is fastened , does the angular velocity of the disc will be same as 1500 RPM , and what happens to the RPM if the disc mass is 50Kg.

Why Airy disc formula has 1.22 in front of it?Does it depend on aperture diameter?Thanks

Hi :smile: A horizontal disc has a hole through its center. A string passes through the hole and connects a mass m on top of the disc to a bigger mass M that hangs below the disc. Initially, the smaller mass is rotating on the disc in a circle of radius r. What must the speed of m be such...

Hi I a building an exhibit for a science museum and hoped I could get some help with the math that is puzzling us. We need to turn three discs that are 1.2m, 0.8 and 0.6m in diameter at a speed of roughly 60rpm. Because it is a musuem they need a clutch and at the minute we are looking at a...

I just got back from playing a round of Frisbee or Disc Golf at my local course and it got me thinking... assuming that there is no wind and standard pressure, would it be possible to predict the motion of the flying disc? to predict where it will land? it's flight path? so far I have...

a disc of radius r we have to find electric flux at a point which is at a distance r from the centre i have used e=(sigma/2eo)(1-x/sqrt(r^2+x^2)) the area da=2pir*dr i know flux=closed integral (e.da) and x=r after that what should i do Reply With Quote

Homework Statement Find the moment of intertia of a pendulum, consisting of a disc free to spin attached to a rod that is hinged at one end. Homework Equations Moment of intertia of rod hinged at end = (1/3)Ml2 Moment of intertia of disc = (1/2)mR2 + ml2 The Attempt at a Solution...

Homework Statement How to calculate braking force generated by eddy currents. If there is a disc of radius r with conductivity K, with a magnet located at a distance r-d from the center of the disc with a magnetic field B, what is the retarding force of the magnetic field created by the eddy...

It is for my university course but I didn't find it worthy of the advanced physics section. Homework Statement A circular metallic disk of radius b rotates about an axis perpendicular to its centre with an angular velocity ω in a constant magnetic field, strength B, which lies in the same...

Homework Statement Work out the moment about the axis of a disc with off-center hole when subjected to a linear acceleration. Homework Equations Parallel-axis theorem The Attempt at a Solution Moment of inertia of offset hole: I_oh=I_h+mr^2 where I_h is MoI of hole about its center...

Is it possbile to spin a disc that has a hole in the centre like normal DVDs but without using a rotating centre shaft that is passing through the hole? The spining disc has to be supported too by a structure. Is there any mechanism to recommend?

Homework Statement I need to find the Moment of Inertia of semicircular disc to do some question. I have done these kind of questions before (Long time ago:shy:) but for some reason i can't recall how, and even when i moved to my new home, i lost my notes :cry: Please can someone put...

Homework Statement Calculate the surface charge distribution on a metal disc of radius R having total charge +q. Homework Equations The Attempt at a Solution

I think i have this right, but would like to confirm i did the right thing: Homework Statement I have a lamina disc radius R with a disc of radius r cut out of it from its centre. Total mass of the actual object is M, Find moment of inertia when lamina rotates about axis perpendicular to...

has the matter in the accretion discs for a black hole entered the BH or is it circling the actual BH?...

Homework Statement We have 3 discs, arranged as the sketch below shows. Find the moment of inertia of the whole system around the axis, passing horizontally through center of the bigger disk: 1. Two smaller disks are fixed and cannot rotate around their axes. 2. Two smaller disks can...

Hi, I have been looking at hoop stresses and the information I have found hasn't been all that useful to me as I am having a hard time converting the thermal contraction of a system into a pressure for the equation (stress=a+b/r^2). This is the thick walled hoop equation The disc is a few...

Homework Statement A thin disc if mass m, centre of mass offset from centre by h (horizontally right in diagram), and radius r rests on a rough horizonal surface. It is originally at rest and then released. No slip occurs between disc and horizontal surface. Write the equations of motions of...

Brake Disc Design- Torque Acting On Wheel Stud Bolts I have currently been working on designing a brake disc assembly. The current problem i am having is trying to workout the force acting on each wheel stud. The frictional force of the brake pad is 3.2 KN with an efective radius of...

Homework Statement I have currently been working on a group project designing a brake disc assembly. The current problem i am having is trying to workout the force acting on each wheel stud. The frictional force of the brake pad is 3.2 KN with an efective radius of 105MM from the center...

Homework Statement A solid wheel of mass M and radius R rolls without slipping at a constant velocity v until it collides inelastically with a step of height h < R. Assume that there is no slipping at the point of impact. What is the minimum velocity v in terms of h and R needed for the...

Homework Statement A large plate is balanced at its center and two students of equal mass stand at its center. The plate is rotated on a frictionless pivot about an axis through its center and perpendicular to its face. The students then begin to walk out towards opposite edges. (Select T-True...