Disc Definition and 374 Threads

Can you show me a metric on the 2 dimensional disc so wild that no open subset can be embedded in R^3?

Hi, I am a little stuck on this question from a PPOD paper I am doing all help appreciated =) Homework Statement A solid circular disc of mass 6.6kg and radius 0.25m rotates about an axis which coincides with its diamter. Its angular acceleration is found to be 6.7rad/s. The axis of...

Why does a Frisbee delivered by a right handed thrower with a back hand release tend to roll to the left? or in general: Why does a flying disc tend to roll in the opposite direction that it is spinning? (see attached image)

hey kinda new to this and I know the rules say I am not allowed to be told how to do this but I am totally stumped and its to be handed in tomorrow. I've looked through everything and cannot find out how to do it anywhere I am starting to think there is a typo in the question paper :S show...

Homework Statement http://scitec.uwichill.edu.bb/cmp/online/P10D/Hunte/Electric%20fields_files/image122.jpg Find the Electric Field at Point P at height z over a uniformly charged disc of radius a with uniform charge Q. Homework Equations The Attempt at a Solution I'm looking...

What is the inner radius of an accretion disc? Is it simply the radius of the smallest possible orbit of a massive particle (the marginally stable radius), 6M ?

Homework Statement The planes x= ±a are charged to uniform surface density ±σ respectively. Find the charge and current densities in a frame moving with velocity (0,v,0) - [done] Find also the electromagnetic field in the moving frame by solving the problem in the moving frame...

Homework Statement The question actually asks for the equation for the magnetic field for the rotating disc; but all I'm after is the direction of the magnetic field. Homework Equations None were given; but I've been using: \nabla \times \vec{E} = -\frac{\partial \vec{B}}{\partial t}...

1. Tim of a mass of 50 kg is standing on a large spinning disc of a mass of 80kg and a diameter of 5m. Tim standing at the edge of the disc which is rotating at 25 rad/s. He then walks to the center of the disc. Calculate the new angular velocity of the disc. 2. IW=I'W' IdiskWdisk + ImitchWmitch...

Homework Statement A 750 gram grinding wheel 25.0 cm in diameter is in the shape of a uniform solid disc. When it is in use it turns at a constant 220 rpm about an axis perpendicular to its face through its center. When the power is switched off the wheel stops in 45.0 s with constant angular...

Hi, I need to find an answer for the following question: What happens when you apply a tangential force instantenously to a disc laying on a frictionless surface? Does it rotate, translate or both? Here is an illustration for a better explanation...

Homework Statement The function is y = 2 - x. The region is bounded by x = 2 and x = 4. Calculate its volume by the shell method by rotating it by the x axis. The Attempt at a Solution This problem has been consuming my mind. I calculated it by the disc method and shell method but I...

Hello, I am working on a rough sketchup for a Mechanical Design Project involving a motorcycle brake. I am working on finding the Contact area of a brake pad on the rotor of a motorcycle. I have already found the torque and forces involved to actuate the pads against the rotor...

how to determine the torque of a rotating disc in order to find the power of motor? there is a rotating disc, and a ball will pass through and launched by the rotating disc. the initial speed is 20m/s, and i could determine the rpm from here. the information i have now: the disc diameter...

I am to design a sensor element that can detect a leakage through a thin metal disc (rupture disc) in a pipeline. Ideally, the metal disc closes the pipeline at the upstreaming side with certain pressure. Its downstream can be either open to atmosphere or close. When a higher pressure occurs...

The discs of all large galaxies show a "flattening" of their discs where the material at the outer edge of the discs rotate at the same rate as the material near the center of the galaxy. The explanation for this is that the galaxy must be embedded in a halo of invisible "dark" matter which, I...

I am trying to understand continuous and discontinuous. These are two assignments I have for a class. I am just looking for some feedback... Let A= {1/n : n is natural} Then, f(x)= (x , if x in A) (0 , if x not in A) This is discontinuous on A but continuous on A...

Homework Statement A thin disc of radius R carries a surface charge \sigma. It rotates with angular frequency \omega about the z axis, which is perpendicular to the disc and through its center. What is B along the z axis? Homework Equations General Biot-Savart law: B(x) =...

Hey - I am a bike mechanic with a large interrest in physics. I know that a larger disc brake rotor provides a greater braking effectiveness, but how can you mathmatically prove it by using physics formulas? And what formulas would be useD? Any ideas would be highly appriciated!

Hi! please help me! I am having a real problem this days about my free space on my local disc C. Sometimes when i turn on my computer i find that the free space on my local disc has diminished itself without that i have saved anything on it before . This is very serious because there is at...

I bought a computer from a store over a year ago and it came with a recovery disc for the OS. i know you can't use the disc on a different computer but can it be used on the same machine if the motherboard is changed out. it seems like it wouldn't since the motherboard and processor are what...

hi everyone. newbie here and i havea question that has to do with my personal experience. Today i jumped off a 50 foot cliff into deep water. the current was calm. i found this cliff at "great falls" virginia. me and a bunch of friends decided to jump off a cliff which was approxomity 50...

You stand on the edge of a large rotating disc. It rotates at a constant speed. You walk towards the centre of the disc. What do you experience? radius is decreasing, therefore inertia and linear velocity are decreasing. but angular acceleration will increase. i don't know if I'm right

Now we know Evo is ok ish i will tell of my latest, While cutting a seized inner bearing off a 60 mm shaft the cutting disc exploded and cut my finger to the bone, luckily i was wearing a a safety mask as a shard cut a grove in it, the last time i used a cutting disc i set my overalls on fire.

Homework Statement Hi all. I can't seem to understand how to apply Lenz' law to a disc rotating in a magnetic field that is perpendicular to the discs plane (see first page on PDF): http://www.pa.uky.edu/~latimer/phy232s08/lectures/phy232l31_4.pdf I can see that using the right-hand...

Consider a disc in the framework of special relativity. It's initially at rest in an inertial frame, and then you get it rotating in a way that respects the symmetry of the circle (e.g. by turning a thin rod through its center). There's no way that the acceleration of the different parts of the...

Homework Statement http://img372.imageshack.us/img372/4379/diagyx7.jpg A uniform disc has centre O,radius a and mass 2m. It is free to rotate in a vertical plane about a fixed horizontal axis through O. A particle of mass m is placed on the highest point of the rough edge of the disc and the...

I am slipping off my spinning disc-- Homework Statement I am taking a non calculus based physics class and have hit a wall with this one. I have a horizontal spinning disc with an Angular Acceleration of .25 rad/s^2 from rest. The disc has a radius of .05 m. A pebble is placed .025m from the...

Homework Statement Finding the area of a disc by integration of rings. Homework Equations A ring of radius r and thickness dr has an area of 2 \pi rdr. The Attempt at a Solution Why isn't it \pi (2rdr + (dr)^2)?

[SOLVED] Convexity of Open Disc I'm trying to prove that the open disc in the complex plane given by D = {z : |z - w| < r} is convex. Let p and q be two points in D. The line segment from p to q is L = {(1 - t)p + tq : 0 <= t <= 1}. Let u be a point an arbitrary point on this segment. If I...

A pendulum hanging from the edge of a horizontal disk rotating around an axis at a constant rate. The angle that the rotating pendulum makes with the vertical increases with the speed of rotation and can be used as an indicator of speed, calculate speed of disck if R = 0.2m, l = 0.3m and the...

Greetings all! There is a bit of a debate in the world of mountain bikes, concerning the conventional 26" wheel diameter versus the rising popularity of the 29" wheel size (nominal diameters). One of the popular beliefs is that the 29" wheel requires a larger brake rotor than a 26" wheel...

Hi, i need calculate the stress energy tensor for rotating 3D-disc in arbitrary rotation. where i can find some hint or perfomed calculations? thank you

Suppose you have a very strong, spinning disc with a diameter of say 10 km in length. At the centre the centripetal velocity is approaching the speed of light, how would we observe the outer edge of the disc to be.

Homework Statement The inner and outer radii of a compact disc are 25 mm and 58 mm. As the disc spins inside a CD player, the track is scanned at a constant linear speed of 1.25m/s. The maximum playing time of a CD is 74.0 min. What is the average angular acceleration of a maximum-duration...

How might one detect the plane of an accretion disc of a Black Hole? Might it just be assumed, by the orbital plane of a BH binary system? http://en.wikipedia.org/wiki/Accretion_disc"

[SOLVED] Moment of Inertia Problem Homework Statement A compound disk of outside diameter 140.0cm is made up of a uniform solid disk of radius 50.0cm and area density of 3.00 g/cm^2 surrounded by a concentric ring of inner radius 50.0cm, outer radius 70.0cm, and area density 2.00 g/cm^2. Find...

I am driving a drum head with a rod. The rod goes up and down as the radius of a disc changes length (please see attached PDF). There is a gradual raise of the drum head, and then an abrupt drop. But there is a kink that the rod needs to overcome. Any suggestions on how to achieve this...

could someone let me know the problems being faced while using disc brakes in any sort of vehicles?

1. If two coins are placed on a rotating disc (constant speed), what forces act on the coins, at what direction and in what proportions? (The coins aren't sliding) Gravity is one, and the normal force is the one counteracting on that. But what forces could be expected in a horizontal...

Hi id just like some info on the type of ceramic used in car brake discs and where i can find its thermal conductivity K? Thanks!

Homework Statement Find the angular velocity and period of oscillation of a solid disc of mass m and radius R about a point on it’s surface. Homework Equations ? The Attempt at a Solution This is really giving me trouble because it seems like a SHO problem mixed with a rotational motion...

Homework Statement Find the potential outside a thin, circular disc with charge q. Homework Equations Laplace's equation DivgradU=0 The Attempt at a Solution Since the problem implies symmetry around phi its obvious the solution doesn't depend on phi. I separate the...

Recently i downloaded a movie but it is in OGM form.And then i tried to burn onto a disc using Nero but it can't.What should i do?

Homework Statement Compact Disc. A compact disc (CD) stores music in a coded pattern of tiny pits 10^-7 m deep. The pits are arranged in a track that spirals outward toward the rim of the disc; the inner and outer radii of this spiral are 25.0 mm and 58.0 mm, respectively. As the disc spins...

I have begun modelling a basic braking system in Simulink/Matlab for my final year project. The model is designed from the time force is exerted to the pedal at a particular velocity, to when heat is produced from the frictional force between the brake pad and disc. I have the modelling...

Hi Does anyone know how changing the diameter of the conducting disc used in Faraday's disc (a homopolar generator) would affect the current and voltage induced in the disc. e.g. would a disc with a greater diameter produce a greater current and voltage than that of a disc with a smaller...

Homework Statement A digital audio compact disc carries data, with each bit occupying 0.6 (mu)m, along a continuous spiral track from the inner circumference of the disc to the outside edge. A CD player turns the disc to carry the track counterclockwise above a lens at a constant speed of 1.3...

Has anyone here heard about the new data storage medium that is being researched? Apparently it'll be able to store up to 3.9 terrabytes of data, which is insane. Anyway, I checked out this article on Wikipedia to see how it worked... http://en.wikipedia.org/wiki/Holographic_Discs...

One more problem on a tough worksheet...I have tried it for a while, but can't find an equation(s) suitable for the problem... A constant force of 12N is applied to the axle of a disc rolling along a flat plane. The disc has mass m=22kg, diameter D=.50m, and rotational inertia I=.688kgm^2...