Disc Definition and 397 Threads

Homework Statement Visible light passing through a circular hole forms a diffraction disc of radius 0.1mm on a screen. If X-ray is passed through the same set up, what will happen to the radius of diffraction disc? The Attempt at a Solution I'm really clueless regarding this question. I...

Homework Statement A charge ##(5\sqrt{2}+2\sqrt{5})## coulomb is placed on the axis of an infinite disc at distance ##a## from the centre of disc. The flux of this charge on the part of the disc having inner and outer radius of ##a## and ##2a## will be A)##\dfrac{3}{2\epsilon_0}##...

Homework Statement I've to demonstrate the electric potential that a charge q feels when it's broght from infinite to a point z. The problem is that every demonstration i found out there starts with the definition of potential eletric as dV = k. dq/ r²; but i cannot use that, 'cause my...

The mass of the disc is M and the radius is R. The problem states: A disc completes 44 revolutions as it slows from an angular speed of 1.5 rad/sec to a complete stop. 1)W/ acceleration constant, what times is required for it to come to rest? 2) what is the angular acceleration...

Is the question in the paint document flawed? The question says. How many socks must he take out to be sure that he has at least two black socks? The solution to this problem is.. in case if all twelve pickings are brown... Well how can he be sure that all twelve pickings are brown? He...

A disc of radius r is spinning about its center in the horizontal plane with a constant angular speed w (omega). A bug walks along the radius of the spinning disc traveling from the center of the disc toward the edge. The bug maintains a constant speed v relative to the disc. (In other words...

Consider a charged wire with constant linear charge density λ. The wire has length 2πa and is attached to the edge of a disc with radius a. In the central region of the disc (a circular region of radius b<a) a constant magnetic field B is applied (perpendicular to the disc). The magnetic...

Here is the experiment in brief for those uninitiated : http://media.uws.ac.uk/~davison/labpage/leedisk/leedisk.html My question is, when the steady state has been obtained (heat flowing into Brass Disc = heat flowing out of it), why do we remove the upper Brass Base and then heat the disc...

Homework Statement Given a disc of radius 'R' with a charge 'h' above the center of the disc, find the electric field on the charge.Homework Equations ##E = \frac{kQ}{d^2}##The Attempt at a Solution I can find the charge density from a ring then integrate over R: ##\sigma = \frac{Q}{A}##...

My solution d. \forallx\existsy(F(x)^S(y) → \negA(y,x)) e. \existsx\forally(F(x)^S(y) → \negA(y,x)) f.\existsx\forally(S(x)^F(y) → A(x,y))

In a different thread the Herglotz Noether theorem was brought up and it was mentioned that this theory implies it is impossible for a cylinder rotating about its vertical axis to remain Born rigid in a gravitational field even at constant altitude. This is an extension of the claim that a Born...

I have an aluminum disc that is 15in in diameter and about 1in thick. I am going to put it in a 400°F oven and I need to know how much the diameter will expand. One of the engineers I work with(i'm an intern) is using what I found to be the linear expansion equation (ΔL/Li=αΔT)...so Length...

Homework Statement A disc is thrown at a 28° angle to the ground. It landed 39.8m away. a) What is the velocity of the disc? b) How long was the disc in the air? Homework Equations ##θ = 28°## ##\vec{Δd}_H = 39.8 m [F]## The Attempt at a Solution a) I was thinking I should use the...

To understand centripetal force due to friction better, I came up with this problem. I'm not entirely sure of my solution, though, so I'd be glad if someone else took it up too and suggested a way to work it out: Two identical blocks, each of mass m, connected by a spring of spring constant k...

A box contains 35 red discs and 5 black discs a disc is selected at random and its color noted. The disc is then replaced in the box. a) In 8 such selections what is the probability that a black disk is selected. i) exactly once ii) at least once b) The process of selecting and...

Homework Statement A disc of conductivity σ is in an axial magnetic field B = B0cosωt The disc has radius a and thickness s Homework Equations possibly dP/dv = JE (dot product of two vectors) but I have absolutely no clue if it is relevant or not. I think J=σE might be relevant, but I...

Hi all, I´m sorry for my sort of trivial issue to solve. Anyway, imagine two discs rotating at the same rpm. They are the same size - same radius, same thickness. The mass is ideally distributed around the axis, so there is originally no disbalance. One of the disc is made of iron, the...

Homework Statement The disc rolls without sliding on the curved surface. What is the velocity of point A attached to the disc? Ans: 1.69 m/s, directed at 45o upwards. Homework Equations v=ωR The Attempt at a Solution v=ωR = 10rad/s * 40mm

Why does an object on a rotating disc fly off the disc as the speed of rotation is increased? To accelerate, the object must experience a net force in the direction of acceleration -- in this case, away from the disc, perpendicular to the object's velocity vector. But what is this force...

this is a practical question I have 14 files to burn on a single layer DVD5 disc in which each of them has a size approximately 4.37GB Those 14 files are of the size (in GB) 2.25 2.25 1.15 3.05 1.16 2.40 0.65 2.05 1.36 1.97 1.11 1.14 2.48 2.65 All values are in GB If...

what is the approximate weight of brake system used in cars? will disc brakes increase the weight?

Homework Statement A uniform circular disc has mass M and diameter AB of length 4a. The disc rotates in a vertical plane about a fixed smooth axis perpendicular to the disc through the point D of AB where AD=a. The disc is released from rest with AB horizontal. (See attached diagram) (a)...

Hi everybody, A seemingly straightforward example from lecture is causing me some confusion. The example was about calculating the angular momentum of a sliding disk (not rolling) about a point on the floor. The result given in lecture says the distance to the point on the floor is unrelated...

Hello, I have some doubts regarding the friction force on a certain situation. Imagine a disc over a fixed flat surface. Like this: The disc has two motions, rotational and translational but these are independent of each other. I mean the translational motion does not come from the...

Homework Statement 1) A small disc of radius R with surface normal ##\hat{k}## is placed a distance z from a point charge −q. Assuming that R ≪ z, derive an expression for the electric flux ##\Phi_E## passing through the disc. 2) Twenty-seven drops of salt water with the same radius are each...

Homework Statement Consider the region of the x-y plane between the line y=7, the curve y=3sin(x)+4 , and for -pi/2<x<3pi/2 Find the volume of the solid generated by revolving this region about the line y=7. I know that for this problem, I will be using the disk method (as the title...

Homework Statement Using work energy theorem, solve: The Attempt at a Solution The actual answer (3.11s) is exactly half of my answer. Does anyone know what I did wrong?

there is a similar case here :https://www.physicsforums.com/showthread.php?t=296966 so I've tried it and what i did was to equate both individual moment of inertia about z axis (and later applied parallel axis theorm) with negative mass for hole. added both these and found out Ix = M/4...

Homework Statement A small disc and a thin uniform rod of length l, whose mass is η times greater than the mass of disc, lie on a smooth horizontal plane. The disc is set in motion, in horizontal direction and perpendicular to the rod, with velocity v, after which it elastically collides with...

The disc brakes of a high performance car are often made of carbon fiber instead of iron, thereby reducing the mass. If both types of discs are of the same size and shape, and each iron disc has a mass of 4 kg and each carbon disc has a mass of 1 kg, what is the reduction in rotational kinetic...

Consider a solid disk made of aluminum with a central hole as shown in the figure - can't include...don't believe it's necessary. The external and internal diameters are found to be 13 inches and 0.6 inches. The disk is 0.5 inch thick. The density of aluminum is 2.70 g/cm3. Question: Calculate...

The first commercial CD release was 30 years ago yesterday, in Japan: Billy Joel's "52nd Street." http://www.cnn.com/2012/09/28/tech/innovation/compact-disc-turns-30/index.html?hpt=hp_bn5 I waited two and a half years before buying my first CD player, for prices to come down a bit and a decent...

Homework Statement An ant positioned on the very edge of a Beatles record that is 14.80 cm in radius revolves through an angle of 70.0o as the disk turns. What is the ant's path length? What is the magnitude of the ant's displacement? Homework Equations L=Rtheta The Attempt at...

Homework Statement The problem is attached in the picture. The Attempt at a Solution I managed to solve it using a different method. I have no idea what the answer is talking about.. My method Found dI of a strip = (1/3)*dm*h2 then i replace h by x, then integrate from -a to...

A pendulum consists of a uniform thin rod of mass 5 kg and length 2 m to which is fixed a circular disc of mass 8 kg and radius 0.4 m. There is a pivot at one end. (a) Find the CoM and Moment of Inertia when the disc is: (i) half way along the rod; (ii) at the opposite end of the rod to the...

Homework Statement There is a vertical 10 inch pipeline with a disc hanging in it. The disc weighs 7.3 kg. There is a flow coming from the opposite direction (water with density 1017.17 kgm/m3) coming at 2250 gpm at 198 psi in the opposite direction (moving up through a pipe). Is there...

Hello , I have to change a car's rear drums to discs . I have the weight at each of the rear wheels . Using DAC I know the max speed and max Decelerations sustained by the car . What are the basic formulae used to calculate the braking forces and the braking distance .

I understand that if we apply a force on the axis of rotation of a spinning disc, the torque is in a different direction, and the axis is moved in a direction perpendicular to the direction in which the force upon the axis was applied, determined by the right-hand rule. But what if the force...

A 36.5-cm diameter disk rotates with a constant angular acceleration of 2.00 rad/s2. It starts from rest at t = 0, and a line drawn from the center of the disk to a point P on the rim of the disk makes an angle of 57.3° with the positive x-axis at this time. (a) Find the angular speed of the...

Dimensions -- Disc Brake Surface Area During frequent braking under race conditions the disk brake rotors on the car described above reach a temperature of 500C. These disk brakes rely on forced convection to cool them. The dimensions of each disk rotor are: outer radius 130mm; inner radius...

Hello everyone, I am a new member here. Nice place you have; I have been reading on here again and again and figured it would be the right place to ask you about a problem I just can't get sorted out myself. It is about bicycles and disc brakes. I have an aluminum track frame that I want a...

Say you have a disc that rotates with angular velocity w. Assume that you know the value of w and the radius of the disc. You drop a particle on the disc while it is rotating half way out from the center of the radius. So the the centripetal acceleration on the particle is Ac(@.5r) = rw^2/2...

Hi, I'm a (very) amateur astrophysicist, and for the past couple of weeks I've been interested in creating a very rough web-based simulation of planetary formation. I've decided to limit the initial scope of this project as much as possible by starting with a VERY rudimentary simulation of a...

Homework Statement This question comes out of "Introduction to Topology" by Mendelson, from the section on Identification Topologies. Let D be the closed unit disc in R^2, so that the boundary, S, is the unit circle. Let C=S\times [0,1], and A=S \times \{1\} \subset C. Prove that...

Hey all, I've been thinking about this all night because it been bothering me I need a proper answer for it... Now I have a disc that has mass on each corner(N,W,S,E) it has a total mass of 1 Killo now with the small object spread on its edges. I want to increase the speed of that disc with...

Hello, From what I've read, I understand that a spinning disc has a torque which resists the tilting of the disc's axis. From what I understand, the higher the angular velocity of the disc is, the more the disc will resist tilting. Can anyone tell me how to calculate this torque? If there is...

Let $f$ be a nonconstant entire function that maps the unit circle, $\{z: |z| = 1\}$, into itself. Prove that $f$ maps the open unit disc, $\{z: |z| < 1\}$, into itself. I am having a little trouble starting this one. z in C

Does there exist a holomorphic function f(z) on the unit disc and satisfies f(1/n) = f(-1/n) = 1/n^3 for every n in N?

Why doesn't $1+z^{2^n}$ have zeros on the unit disc?

Have a 88 monte carlo racecar, reciently installed a 9in ford with disc brakes using metric calipers, can't use aftermarket master cylinders or proportonal valve, an have a problem with no rear braking, tried a corvette master cyclinder but didnt seem to help, any ideas??