Disk Definition and 819 Threads

Homework Statement I have that system and the problem says: A disk of mass M and radious R are posed are shown. The disk is hanging by an ideal rope which is coiled up. From a smooth axis through the center of the disk is haning a body m. Calclate the module of the aceleration of the...

Hi! I'm trying to give a few examples of symmetric manifolds. In the article "Introduction to Symmetric Spaces and Their Compactification" Lizhen Ji mentions the Poincaré disk as a symmetric space in the following way: D = \{z \in \mathbb C | |z| < 1\} with metric ds^2 =...

Homework Statement Ive been working on this two last questions and I can't seem to get the right set up. A disk with a diameter of 0.04 m is spinning with a constant velocity about an axle perpendicular to the disk and running through its center. -How many revolutions per second would it...

If an aluminium disk is placed above a COMPLETELY vertical current carrying iron rod will any flux link with the aluminium disk... Firstly, does it matter if the current is AC or DC. I presumed not as the only difference is that the magnetic field will vary in one case and stay constant in...

Homework Statement The circular plate has a weight W and a center of gravity at its center. If it is supported vy three vertical cords tied to its edge, determine the largest distance d from the center to where any vertical force P can be applied so as not to cause the force in anyone of the...

Homework Statement A compact disc speeds from rest to 5200 rpms in 620 rad. Diameter is 5.0cm -how many revolutions did it make in this time -what is the angular acceleration in rad/s^2 -how long does ti take to reach this speed Homework Equations The Attempt at a Solution i was able to find...

Hello, When you look at the accretion disk around NGC 4261 (see here), you can read that the dark, dusty disk represents a cold outer region which extends inwards to an ultra-hot accretion disk with a few hundred million miles from the suspected black hole. So, from the outside, you have...

Homework Statement Homework Equations I=mr^{2} L=ωI ω=\frac{L}{I} The Attempt at a Solution I thought that since the moment of inertia was larger for the ball on the outside its angular speed would be slower. So then it would take longer to hit the wall.

Homework Statement A very thin disk of non-conducting material initially holds a charge QO = +5 μC that decreases with time t as Q(t) = QO e-t/τ where τ = 10 seconds. If the disk has a radius of 0.10 m, what is the magnitude and direction of the magnetic field at the circumference of...

Homework Statement http://dl.dropbox.com/u/630750/Screen%20Shot%202012-04-26%20at%2010.03.36.png Homework Equations The Attempt at a Solution http://dl.dropbox.com/u/630750/Photo%2026-04-2012%2010%2001%2034.jpg I know this is wrong but I can't really see why, can anybody...

A disk and a box of equal mass are released from the top of two inclines both of which are a height h above the ground and make an angle θ to the horizontal. Let the radius of the disk be R. How much sooner does the box reach the bottom of the incline than the disk? Express your answer in terms...

Homework Statement Suppose f : ℝ→ℝ and g : ℝ →ℝ are continuous. Suppose that f is odd and g is even. Define h(x,y) : f(x)*g(y). Let D be a disk centered at the origin in the plane. What is ∫∫h(x,y)dA? D The Attempt at a Solution I know there's probably a trick to it. Is it 0...

Homework Statement Find the moment of inertia of a uniform disk of mass m and radius r about an axis normal to the disk, through a point x from the centre. Homework Equations The Attempt at a Solution Let ρ be the density. I=ρ∫r^2 dA=ρ∫∫r^3 dr dθ in polar coordinates. However I...

A disk with mass m and radius R is rolling down a hill with no slipping, until it reaches a wall and then stops: I want to write a set of equations describing the position cordinates x and y of the disk's center of mass (point A) and the cordinates for point B. mgsin(theta)=ma ->...

The electromagnet stick always head N/s, no matter how fast the rotation of the shell of the disk is, you just need to control the input voltage of it, and it will not get heavy if the Magnetic stronger. I think the input higher voltage can make it head with power and hard to change the...

Homework Statement Use the Poincare (disk) model to show that in the hyperbolic plane, there exists two points A, B lying on the same side S of a line l such that no circle through A and B lies entirely within S. Homework Equations The hint was to use this proposition: A P-circle is a...

Homework Statement A spinning disk is rotating at a rate of 30 rad/s in the counterclockwise direction. The disk is slowing down at a rate of 6 rad/s2. Find the angle through which the disk has turned after 3 s in radians, degrees, and revolutions. Homework Equations θ=θi + ωi*t + αt^2...

Homework Statement Derive the moment of inertia of a solid, uniform density, disk rotating about a diameter using vertical rods. Diagram: http://i.imgur.com/TQIjz.png Only the radius of the circle and the inertia of a thin rod is given Homework Equations Inertia of thin vertical rod = m*r^2...

Homework Statement A circular disc of radius a is heated in such a way that its perimeter r=a has a steady temperature distribution A+B \cos ^2 \phi where r and \phi are plane polar coordiantes and A and B are constants. Find the temperature T(\rho, \phi) everywhere in the region \rho < a 2...

Problem Statement: I'm having some trouble understanding how to write charge densities using delta functions, particularly when they involve geometries other than Cartesian. So I have a disk moving with velocity v (along the z-axis) that has total charge Q, and I'm trying to write ρ(x,t) so that...

I'm trying to figure out the intensity of light in different sections of a 2d airy disk from a point source, but I'm not sure how to calculate it. Does anyone have any good sources?

Homework Statement The problem can be found in Jackson's book, I think in chapter 1 problem 3 or something like this. I must determine the charge distribution of a uniformly charged disk of radius R in spherical coordinates (I've done it in cylindrical coordinates and had no problem). The...

Assumed a disk loaded with external pressure Po, internal Pressure Pi and rotating at the speed ω. I'm sure that average tangential stress for uniform thickness rotating disk can be calculated using equation below : σ avg = (PiRi/Ro-Ri) - (PoRo/Ro-Ri) + (ρω^2) / 3(Ro^2+RoRi+Ri^2) Ro = outer...

Homework Statement A disk of radius R has a uniform surface charge density σ. Calculate the electric field at a point P that lies along the central perpendicular axis of the disk and a distance x from the center of the disk. Homework Equations Electric field due to a continuous...

A non-conducting disk has radius 1.25cm and charge 6.55nc. What is the electric field (magnitude) experienced at a point P - where p = 2cm and is on the x-axis. The disk's centre is placed at the origin. I approached this problem using the general formula derived: k/2Σσ [1 -...

A string is wrapped around a disk of mass 2.1 kg (it's density doesn't have to be uniform). From rest, you pull the string with a constant force of 9 N. At this instant, the center of mass has moved 0.11 m, and your hand has moved 0.28 m. 1. At this instant, how much rotational kinetic...

Homework Statement A uniform disk with mass m = 9.32 kg and radius R = 1.37 m lies in the x-y plane and centered at the origin. Three forces act in the +y-direction on the disk: 1) a force 340 N at the edge of the disk on the +x-axis, 2) a force 340 N at the edge of the disk on the –y-axis...

So we were taking measurements for an experiment in our radio astronomy lab. For the first part of the experiment, we recorded the intensity of a far away point source ( the signal from a TV satellite was used for the point source ) detected by commercial satellite dish and receiver. When we...

Homework Statement Show that the gravitational field due to a horizontal uniform thin disc (thickness D, radius R and density r) at a distance h vertically above the centre of the disc has magnitude 2πGρd(1-h/(R2+h2)1/2) A pendulum clock in the centre of a large room is observed to keep...

Homework Statement How much torque is required to rotate a disk or diameter 1.4cm, height 1cm, weight 12g? Homework Equations I think Iz = mr^2/2 Torque = force x distance The Attempt at a Solution Iz = 2.95 * 10^-7 I do not know where to go from here. Thank you.

Now I am designing a piezoelectric droplet generator. The problem I am facing now is that the vibrational amplitude of the piezoelectric device is not sufficiently great. I do not know how to determine the voltage applied to the piezoelectric disk for my droplet generator. Can someone provide me...

I'm trying to connect a disk from a brake to a shoulder using self locking screws but can't find a formula that would help me to calculate the torque these screws would be subjected to or how many bolts I would need. What do I need to do?

Homework Statement I apologize if this is not the right place to put this. If it is not please redirect me for future reference. 11. Consider a uniform thin disk that rolls without slipping on a horizontal plane. A horizontal force is applied to the center of the disk and in a direction...

Homework Statement A cathedral dome is designed with three semi circular supports of radius r so that each horiontal cross section is a regular hexagon. Show that the volume of the dome is r^3 * sqrt(3) an accompanying figure - http://imgur.com/3fSqh Homework Equations...

Homework Statement A disk of radius 2.30 cm has a surface charge density of 5.22 μC/m2 on its upper face. What is the magnitude of the electric field produced by the disk at a point on its central axis at distance z = 11.2 cm from the disk? Homework Equations Formula for an electric...

Homework Statement A circular disk with a rectangular hole has a radius of 0.620 m and mass of 0.470 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 = 1.60E-1 kgm2. Its center of mass is located at a distance of s=0.120 m...

Hello, I am trying to determine the calculation to use to determine the force at which a disk plate will fail for the following set up. The disk is slid onto a metal bung for a roll, the disk is supported from the inside diameter for around 50mm. A force is then applied on the oppsite side...

How fast a disk is rotating? Please help me Im trying to attempt this problem, its not a assigned homework problem but it has 2 stars beside it(which means its one of the harder ones) in the book so I am trying to solve it but i don't even know how to begin and have a crack at it. I really...

Hi there, does anyone knows the overall dimension for 2.5' hard disk drive?including all the components inside. who has the complete dimension? tq =)

Two unequal masses m and 2m are attached to a thin bar of negligible mass that rotates about an axis perpendicular to the bar. When m is a distance 2d from the axis and 2m is a distance d from the axis, the moment of inertia of this combination is I. If the masses are now interchanged, the...

I don't understand when acceleration is constant and when it changes. What are some examples of situations where the acceleration is constant and when it's not? Is acceleration constant when a disk is rolling down a ramp?

Hello I have been modeling the rotation curves of galaxies. Can help in calculating the rotation velocity for a thin exponential disk. I use the method of Kent S. http://articles.adsabs.harvard.edu//full/1986AJ...91.1301K/0001310.000.html My implementation in C #...

Homework Statement A computer disk drive is turned on starting from rest and has constant angular acceleration. If it took 0.690s for the drive to make its second complete revolution, how long did it take to make the first complete revolution? What is the angular acceleration?Homework Equations...

I have the working for part d) but I don't understand certain parts, so my problems lie with part d), f) and g) Homework Statement 3. A solid wooden disk is suspended as shown: it has mass 7.70 kg and radius 0.219 m . It is rotated from rest about its vertical axis, reaching an angular...

This is not a homework question! I am observing that a thin, flat disk made from a material whose density is gradually increasing, shrinks in the radial direction (of course) but appears to grow very slightly in the z-direction. The change in density is supposed to be isotropic. Is growth...

Homework Statement What is the moment of inertia of an 8 kg, 40 cm diameter disk for rotation through the edge of the disk? Homework Equations I = \frac{1}{2}MR^2 The Attempt at a Solution Inertia at the center of the disk would be I = \frac{1}{2}MR^2, right? I'm not sure what...

Homework Statement I came across an expression in the following pdf at the bottom of page two: http://iweb.tntech.edu/murdock/books/v4chap2.pdf Homework Equations The electric field for a disk: \vec{E} = \frac{\sigma}{2{\epsilon}_{0}} ( 1 - \frac{z}{\sqrt{{z}^{2} + {r}^{2}}}) Now logically...

A solid uniform disk of mass 19.0 kg and radius 70.0 cm (.7 m) is at rest FLAT on a frictionless surface. A string is wrapped around the rim of the disk and a constant force of 35.0 N is applied to the string. The string does not slip on the rim. The string is being pulled. When the disk has...

If I have an ellipsoidal disk, where the demagnetization constants Nd_{xx}>>Nd_{yy}>>Nd_{zz}. The disk lies on the y-z plane and easy axes are +z or -z. The energy of the system (just considering demag fields) will be U=Nd_{xx}sin^2\theta cos^2\phi + Nd_{yy}sin^2\theta...

I'm taking a probability class where multivariate calculus was not a prerequisite, but some of it is coming up, I get the concept of, say integrating over a region, but get lost in some of the mechanics Here is the problem (I don't want a full solution): A point is uniformly distributed...