Disk Definition and 783 Threads

Homework Statement Homework Equations Newton's 2nd Law F = ma Torque Equation τ = Iα The Attempt at a Solution Well I know I have to write separate equations for the masses and tensions so I got this: T1 - m1g = m1a T2 - m2g = -m2a -----> (negative because acceleration...

Hi all, I'm treating a problem concerning a disk containing an additional point mass on the edge. The disk is moving (rotating and translating) relative to another fixed point, meanwhile it's spinning about its axes of symmetry. I'd like to determine the instantaneous angular momentum about...

Homework Statement In the figure, a string is used to pull a disk of radius 18 cm and mass 9.3 kg. If the incline is 37° and the tension in the string is 20 Newtons find the acceleration of the disk and the force of friction on it. Homework Equations T=I(alpha) The Attempt at a...

Homework Statement A uniform disk turns at 8.6 rev/s around a frictionless spindle. A nonrotating rod, of the same mass as the disk and length equal to the disk's diameter, is dropped onto the freely spinning disk, see the figure. They then turn together around the spindle with their centers...

Homework Statement As per Griffiths 3.21, I am given the on axis potential a distance r from a uniformly charged disk of radius R as a function of \sigma. Using this and the general solution for laplace's equation in spherical coordinates with azimuthal symmetry, calculate the first three...

hi the airy disk equation is d= 1.22 lambda / NA my question is: lambda is the wavelength in medium or in vacuum? thanks in advance

I posted this in the Intro physics sections, but then realized that spherical coords might be a bit complex for introductory physics. This has been bothering my head for a couple days now. Any help is appreciated. Given: A wheel of radius R rotates with an angular velocity. The wheel lies in...

how do i calculate the power produced by a rotating disc? for example given that the constant angular velocity is 30rad/s, diameter of disc is 0.5m, mass is 15kg. or do u need more data to calculate the power? if yes, what data do u need?

Homework Statement 4. Let w = f(z) = i(\frac{1-z}{1+z}). Show that f maps the open unit disk {z \in C | z < 1} into the upper half-plane {w\in C|Im(w) >0}, and maps the unit circle {z\in C||z|=1} to the real line. Homework Equations I was given this hint: "set w=i(\frac{1-z}{1+z}) and...

This is my first post on this forum because I have a question that I cannot seem to answer myself. At my working place we have a machine where a metal conveyor belt is running through a section of the machine where the temperature is constant at 320 degrees Celcius. On this conveyor belt are...

Homework Statement I have to show that the Poincare disk satisfies the incidence axiom that any line contains at least two points. Homework Equations There are two kinds of lines on the Poincare disk. I've found 2 points for the first kind, which are straight lines going through the...

Homework Statement Consider the solid obtained by rotating the region bounded by the given curves about y=10 Find the volume V of this solid using DISK METHOD Homework Equations y=5e^-x, y=5, x=4 The Attempt at a Solution setting up the picture easy. but I'm having...

For circular region, why is \frac{\partial}{\partial n}G(r,\theta,r_0,\phi)= \frac{\partial}{\partial r_0}G(r,\theta,r_0,\phi) ? Where \; \hat{n} \: is the outward unit normal of C_R. Let circular region D_R with radius R \hbox { and possitive oriented boundary }\; C_R. Let u(r_0,\theta) be...

Recently there was information that military is developing a nutating disk engine http://en.wikipedia.org/wiki/Nutating_disc_engine" which, as they hope, will have higher power density, than reciprocating engine.Also some people say,that this is low friction design. Does anyone know what is...

Can an accretion disk get dense enough to start fusion? How dense does something have to be in order to start fusion? Does it depend on the material? is there a way of measuring the density of accretion disks?

I think I'm not understanding something about this problem. Can someone help me out? Homework Statement A 2.0 kg disk traveling a 3.0 m/s strikes a 1.0 kg stick of length 4.0 m that is lying flat on nearly frictionless ice. The disk strikes the endpoint of the stick, at a distance r = 2.0 m...

Homework Statement An electron (e) is to be released from rest on the central axis of a uniformly charged disk of radius R. The surface charge density on the disk is +3.50 µC/m2. (a) What is the magnitude of the electron's initial acceleration if it is released at a...

I heard it's quite hard to prove that electric charge is distributed uniformly on a disk conductor. Can you point me to some resources online on the subject?

This is a significant discovery that something is fundamentally controlling and ordering the properties of spiral and disk gaseous galaxies. Elliptical galaxies have no gas and no star formation. The question is not only what but how is the unknown parameter controlling spiral and disk galaxy...

Homework Statement A uniform circular disk has radius 36 cm and mass 350 g and its center is at the origin. Then a circular hole of radius 7.2 cm is cut out of it. The center of the hole is a distance 10.8 cm from the center of the disk. Find the moment of inertia of the modified disk about...

Homework Statement A uniform disk of mass Mdisk = 4.9 kg and radius R = 0.2 m has a small block of mass mblock = 2 kg on its rim. It rotates about an axis a distance d = 0.17 m from its center intersecting the disk along the radius on which the block is situated. a) What is the moment of...

hello imagine a disk rotating by an axis that passes through the center of the disk how can we find the analogue of a mass rotating by an axis? I mean, how can we lump the whole mass of the wheel to a point? how much will be the distance of this point from the axis? for example to...

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...

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...

A large flat disk with moment of inertia I is spinning with angular speed 18 rad/s a small object lands on the disk and changes the moment of inertia to 1.5I what is the new speed? i used L=I\omega to give me 18*1.5=27 rad/s i used this because L is the angular momentum of the disk and...

Laplace equation: \frac{R''}{R} + \frac{1}{r}\frac{R'}{R} + \frac{1}{r^2}\frac{\Theta''}{\Theta} =0 Which give: r^2\frac{R''}{R} + r\frac{R'}{R} - \lambda R =0 \;and\; \Theta '' + \lambda \Theta =0 \theta \;is\; 2\pi \;periodic\; \Rightarrow\; \Theta \;is\; 2\pi \;periodic\...

Homework Statement A thin, 50.0 g disk with a diameter of 8.00 cm rotates about an axis through its center with 0.190 J of kinetic energy. What is the speed of a point on the rim?Homework Equations C = \frac{1}{2}MR^2 K_{rot}=\frac{1}{2}I\omega^2The Attempt at a Solution Since the formula for...

Homework Statement A thin metal disk of mass m=4.50 g and radius R=2.70 cm is attached at its center to a long fiber. When the disk is turned from the relaxed state through a small angle theta, the torque exerted by the fiber on the disk is proportional to theta. Suppose the disk is twisted...

Consider a rotating disk on a uniform magnetic field. Faraday's law states that \epsilon = - \frac{d\phi}{dt} In this situation, \vec B is constant and the area of the disk is constant. Hence, the magnetic flux is constant and there should be no emf. What am I missing?

Homework Statement A circular disk has two masses acting on it, m1=10g, m2=50g. The forces caused by these masses are 4.5cm (F1) and 6.8cm (F2) away from the axis of rotation (center). The angles are 130 degrees (F1, and on outer side away from center) and 98 degrees (F2, also on outer edge...

Homework Statement A very thin conducting disc of radius a and conductivity \sigma lies in the x-y plane with the origin at its center. A spatially uniform induction is present and given by B=B_0 cos\(\omega t \)\hat{z}. Find the induced current density \vec{J} in the disc. Homework...

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...

Homework Statement In the open unit disk D = {(x,y)|x2 + y2 < 1} give a forumla for: (a) \frac{\partial \sum ^{inf}_{n=0} (xy) ^{n}}{\partial x} (b) \frac{\partial (e^{x+y} \int ^{y}_{x} e^{-t} dt)}{\partial y} Homework Equations The Attempt at a Solution...

Homework Statement A super nova releases 1.9E45 J of energy over a 10 day period. It is 1560 ly from earth. A detector, facing the star, is a disk of radius 7cm. How much energy reaches the detector? (The detector is in orbit, so it can face the star for the entire 10-day period) Homework...

Resistance=resisivity(of a certain material)Xlength/cross-sectional area resisivity is expressed in ohm-cm I have a graphite material that is 6ohm-cm the material is .032" thick I will cut the graphite material into a 3' disk I will place an electrode in the center of the disk and have...

[b]1. A computer hard disk starts from rest, then speeds up with angular acceleration of 218 rad/s^2 until it reaches its final angular speed of 6660rpm. How many revolutions has the disk made 10.1s after it starts up? [b]3. The Attempt at a Solution . I have no idea how to find the...

Homework Statement Revolve the region under the curve y =√x on the interval [0, 4] about the x-axis and find the volume of the resulting solid of revolution. YET, NOW, I want to do in respect to y Homework Equations integral formula The Attempt at a Solution I did dx and I...

The circular blade on a radial arm saw is turning at 265 rad/s at the instant the motor is turned off. In 12.0 s the speed of the blade is reduced to 85 rad/s. Assume the blade to be a uniform solid disk of radius 0.140 m and mass 0.400 kg. Find the net torque applied to the blade. Relevant...

Homework Statement Use the functions: y=x+1, y=0, x=0, x=2 Find the volume when rotated around y=3 Find the volume when rotated around y=-1 Homework Equations PI\int R2dx or perhaps PI\int R2 - r2dx The Attempt at a Solution i don't think that this is a particularly hard question, but I...

1. a clever engineer solves the high velocity exploding flywheel problem (structure fails) and any other serial problems. 2. therefore a bench top a. torus, b. disk, c. cylinder spinning about its axis with a tip speed approaching c 3. what will happen to space time and gravity or anything...

Hi When I was a kid, the largest telescope was Mt Palomar, a little over 5 meter diameter mirror. In spite of its large size, I always read that stars appeared as points of light through the scope if it were used visually, i.e. stars are too small and too distant to appear as disks. However...

Homework Statement A disk of mass m and radius a is suspended horizontally by a rod bored through the disk at a location d distance from the center. When in equilibrium the center of the disk is directly below the rod. Obtain an approximate expression for the period, ignore disapative...

Homework Statement http://online.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?courses/phys211/oldexams/exam3/sp08/fig10.gif What's the net torques about the pivot, represented by the dot (•), in the diagram D. The solid arrows represent the magnitude and direction of the forces...

Homework Statement A charge of -5.00 nC is spread uniformly over the surface of one face of a nonconducting disk of radius 1.15 cm. Find the magnitude of the electric field this disk produces at a point P on the axis of the disk a distance of 3.00 cm from its center.Homework Equations Surface...

Homework Statement The overall question is to construct an asymptotic approximation for a harmonic field on a rectangle with a small disk. However, I'm having difficulty finding the unperturbed field. Perhaps I've been staring at it for too long, but I can't seem to find a solution. The...

I'm having a brain freeze and have a hard time understanding why the area of the ring is 2*pi*a*da. Can someone explain why it is the circumference times da? Link to derivation: www.phys.uri.edu/~gerhard/PHY204/tsl36.pdf

When a string is wrapped around a disk and pulled taut to rotate the disk, such as in a pulley, how can tension be the force producing the torque? Tension would only act upon the string next to the disk. I suppose there would be the normal force of the disk on the string, but that wouldn't...

Sorry I don't know latex so this may look a little messy. Homework Statement I'm trying to solve the equation for null geodesics of light traveling from a rotating black hole accretion disk to an observer at r = infinity. The point of emission for each photon is given by co-ordinates r, phi...

Well, I had a couple problems on my final I was hoping to go over- hope nobody minds. Here's the second. Homework Statement A nonuniform disk of radius R and mass m has the center of mass at a distance A from the geometrical center. Its moment of inertia about the axis passing through the...

How is it formed? How do particles move on it?