Disc Definition and 374 Threads

Homework Statement A horizontal thin disc of mass M and radius R rotates about its horizontal axis through its centre with angular speed w. If a chip of mass m breaks off at the edge of the disc, what is the final angular speed of the disc? Homework Equations Initial rotational...

Homework Statement A uniform circular disc at rest has mass 10 kg and radius 0.2m. When a force of 10 N is applied tangentially to the disc for 10s, calculate the angular velocity. Given the moment of inertia, I=1/2 mr^2 Homework Equations The Attempt at a Solution Using...

Homework Statement This is not a homework question but it could be. I am trying to understand why the moment of inertia of a thin disc about its axis of rotation is 1/2 MR2. Homework Equations The rotational moment of inertia of a system of points is ^{}\summr2. The Attempt at a Solution...

Homework Statement Consider a rigid rod-plus-disc system Find the moment of inertia of the pendulum as it freely rotates about the point P. The rod has a length 0.62 m, and the disc has a radius half that. The pivot at P is a fourth of the way from the end of the rod. The rod has a mass of...

The EMF for the Faraday disc is calculated as \epsilon = \int_0^R \textbf{v} \times \textbf{B} \cdot d\textbf{l} the integration is between the disc axis (0) and its edge (R is the disc radius). As for uniformly rotating disc \boldmath v = \omega \times r and B-field is orthogonal to the...

Homework Statement consider a disc of radius 1 in the plane D in R^2 D = {(x,y) in R^2 | x^2 + y^2 <=1 } what is the marginal pdf of x and y Homework Equations The Attempt at a Solution so the joint distribution of xy is 1/Pi for x^2 + y^2 <=1 right? but how exactly? "density"...

Homework Statement Consider a disc of radius 1 in the plane D in R D = {(x,y) in R | x^2+y^2 <= 1} write the marginal pdf of x and y Homework Equations The Attempt at a Solution so the joint pdf is 1/Pi for x^2 + y^2 <= 1 <- correct? but how to I get the marginal pdfs?

1. Homework Statement Here is the link to the old thread, https://www.physicsforums.com/showthread.php?t=349730 i tried posting but it doesn't seem active. I don't understand how they get the second pdf as i tried it and got the first pdf. I also don't know how to do the double integral as...

According to this website, particles of the disc that are located at the point of contact between the ground and the disc have a velocity of zero, and the velocity of each of the particles increases as you move from the bottom of the disc to the top of the disc. How is this possible? I always...

If I have an series of discs within each other (imagine a bunch of o's within each other, the outer one the largest, the inner-most one the smallest, and I am not limited in quantity), each spinning in the same direction and each spinning from a motion source in the disc just outside it so that...

Hello, I would like to know how to determine the max RPM of a disc. I would think it would be the centrifugal force against the Yeild Strength. Any help would be appreciated. Thanks, Ron

I hope this is the right place to ask this. for a long time I wondered why our galaxy, or all galaxies for that matter, is more or less shaped like a disc. I assume this has something to do with the way gravity works. Yet I also assume that the simplest shape gravity would form is a sphere...

Theres a few key concepts about the disc and washer method that I can't quite grasp and I was hoping if I could get a bit of clarification. 1) How do you find your outer and inner radius? I can provide an example if needed. 2) If a problem has its function, for example f(x)= sec x...

I may have a herniated disc in my spine. I am currious by what actions the body repairs the disc? Is the ruptured material of the disc reabsorbed into the body? Can a flattened disc grow thicker with rest, does this happen while we sleep? I Have re injured my back 5 or 6 times to varying...

Homework Statement Find the maximum of |ez| on the closed unit disc. Homework Equations |ez| is the modulus of ez z belongs to complex plane Maximum Madulus Theorem - Let G be a bounded open set in complex plane and suppose f is a continuous function on G closure which is analytic in...

see diagram a circular disc of radius r has an initial angular velocity \omega and rolls down a quarter circle ramp of radius R. The initial angular velocity will be very high (e.g. 10,000 RPM) causing the disc to slip. The normalised longitudinal force (i.e. longitudinal force / maximum...

Gravitational Disc consequence!? It there some kind of reason why the solar system is in the shape of a disc, as we'll as some galaxies? Is there a gravitational consequence which result equatorial orbits?

1. f(x)= 3x2-12x / x2-6x +8 f(x) can be made continuous at x =4 by defining f(4)=6 I know that the removable disc. is at x=2 and the non removable is at x=4. So there is an asymptote at x=4. How is it possible to define it there?

How many permutations of the letters ABCDEFGH contain the string ABC? This is an example problem in my book, and the answer is 6! = 720. Could someone please explain to me the reasoning behind this (my book does a poor job explaining)? And would this reasoning apply if the string to be...

1. The problem statement, all variables and given known data A solid disk of radius 1.60 m and mass 2.30 kg rolls without slipping to the bottom of an inclined plane. If the angular velocity of the disk is 4.9 rad/s at the bottom, what is the height of the inclined plane? Homework...

In my Cal 2 class we learned the disc method to rotate an area around an axis to obtain a volume. However we only rotated a function around either the x-axis or y axis. Let's say I take the function y=x2and y=x from the interval 0 to 1 and I want to rotate the area between these functions...

Homework Statement 1. How many strings of eight English letters are there if no letter can be repeated? 2. How many strings of eight English letters are there if X is the first letter and no letter can be repeated? 3. How many strings of three decimal digits do not contain the same digit...

Homework Statement A 200 g, 42.0-cm-diameter turntable rotates on frictionless bearings at 56.0 rpm. A 20.0 g block sits at the center of the turntable. A compressed spring shoots the block radically outward along a frictionless groove in the surface of the turntable. What is the...

Homework Statement A uniform disc radius a, mass m there is rotation about an axis (z) tangental to the disc and in the plane of the disc. a point mass m is placed at the centre of the disc. what is the new moment about the axis z also show that the period of oscillations will...

The disc in question is {z: |z|<(n+1/2)pi}. I can't figure out how to apply Rouche to this. Any help would be appreciated. (This is in the context of showing all roots of zsin(z)=1 are real. I counted the zeros of zsin(z)-1 on the real axis and got 2n+2, and now I hope to get the same answer...

I've been trying to figure out the friction coefficient of some brake pads. My test fixture only allows me to pull (F2) a brake disc between two brake pads clamped around the disc with a force F1. I then measure with a load cell the maximum force required for the brake disc to slip. My...

Homework Statement Show that if a, b, c, and d are integers such that a | c and b | d, then ab | cd. Let m be a positive integer. Show that a mod m = b mod m if a ≡ b(mod m) Homework Equations | means "divides," so a | b means "a divides b" or "b can be divided by a" mod gets the...

Homework Statement S = { z | |Im(z)| < 5 }, z is a complex number Homework Equations I am trying to generate a mobius transformation w = f(z) such that it will map S onto a unit disc but I keep running into problems and contradictions. I think there is a big mistake in my attempt but I...

I have read that locomotives use eddy current braking systems, and one article mentioned that this system has also been used to charge batteries in a recovery circuit. However, I can not find details on this idea. From what I understand, the train has conducting discs attached to the wheels, and...

Homework Statement A disc has radius a and rotates with angular frequency w. Magnetic flux density is B. Such a disc of mass 10^4 kg and radius 3m is rotating freely at 3000 revs/min in a field of 0.5T. A load of 10^-3 ohms is connected suddenly between the rim and the axis of the disc...

I already have Windows XP on my computer right. OK, so I was wondering if I could buy it and then install it over again. Would it delete all of my old files so that I could restart over from the ground up? I can't do System Recovery or System Restore (my pc is infected). I can barely boot the...

Homework Statement A solid uniform disk of mass 21.0 and radius 85.0 is at rest flat on a frictionless surface. The figure shows a view from above. A string is wrapped around the rim of the disk and a constant force of 35.0 is applied to the string. The string does not slip on the rim...

Regarding electric field at the center of a uniformly charged disc? The electric filed at a distance x from the center of a uniformly charged disc of radius R,along the axis passing through the center is given by E = sigma/2e(1-x/rt(x^2+R^2)) where sigma is surface charge density and e is...

im struggling abit with this question. i have a formula but it doesn't really go with my question a brake disc has the following specification mean radius 0.16m force applied to each pad 5045N U = 0.35 brake disc rotational speed is 550rev/min work out its frictional torque work done...

I am trying to write a simulation program for a relatively complicated mechanical system. Parts of it will be strings wrapped around discs under tension - with the discs moving and rotating. So, I decided to figure out the basics, and am stuck. The situation is thus: An unstretchable...

Homework Statement A) a horizontal disc of diameter 12.0cm is spinning freely about a vertical axis through its centre at an angular speed of 72 revolutions per minute. a piece of putty of mass 5.0g drops onto and sticks to the disc at a distance of 4.0cm from the centre. The angular speed...

Homework Statement I need a quick sanity check here please. (Sorry, my alphas keep coming out as power signs, they're not!). To find the force to slow a spinning disc with known moment of inertia (0.0004kgm2) and known angular velocity (120pi rad/s) to a stop in 6s. Here, the...

1. Find the Moment of Inertia of a Quarter Disc which has mass M and radius R about the axis passing through the center (of original disc) and perpendicular to the plane. 2. The attempt at a solution I found the Moment of Inertia (I) of a disc about the axis passing through the center...

Homework Statement Given \epsilon > 0 , show that the unit disc contains finitely many dyadic squares whose total area exceeds \pi - \epsilon , and which intersect each other only along their boundaries. Homework Equations The Attempt at a Solution I've tried to solve this...

How far has the disk moved? Disk has .34m radius with a mass of 7.4. The angular acceleration about the center of mass is 100.2 rad/s2. So this is what i did: ang. disp= .5(ang. accel)*t^2 (x=.5(a)t^2 =>pretty much) I got my ang. disp to be 84.669 rad. Now i need to convert it to meters. The...

Homework Statement \D = \{(x,y) \in \mathbb{R}^2 | x^2 + y^2 \leq 1\} i.e. a disc or radius 1. Write down the pdf f_{xy} for a uniform distribution on the disc. Homework Equations The Attempt at a Solution f_{xy} = \frac{(x^2 + y^2)}{\pi} \mbox{for} x^2 + y^2 \leq 1 0...

Homework Statement \D = \{(x,y) \in \mathbb{R}^2 | x^2 + y^2 \leq 1\} i.e. a disc or radius 1. Write down the pdf f_{xy} for a uniform distribution on the disc. Homework Equations The Attempt at a Solution f_{xy} = \frac{(x^2 + y^2)}{\pi} \mbox{for} x^2 + y^2 0 \mbox{otherwise} as the...

Hey Folks I have rather a silly doubt i guess... It goes like this Consider a disc rotating about a fixed axis with constant angular velocity. Which means it has no angular acceleration ie it must be 0. Now since Torque=(moment of inertia)*(angular acceleration). hence the torque acting on...

Homework Statement Find the power-series expansion about the given point for the function; find the largest disc in which the series is valid. f(z) = z^3 + 6z^2-4z-3 about z0=1. Homework Equations The Attempt at a Solution The series is fine. Since it's a polynomial, there are only three...

Homework Statement a disc drive at rest is powered up and accelerates according to alpha=alpha(i)sin(bt). this lasts for 1.66 seconds after which it no longer accelerates. alpha(i)=506 rad/s^2 b=1.89 radius of disc=3.9cm. After the disc is done spinning up what is the centripetal...

Homework Statement When powered up, a disk drive starts at rest and spins up with non-uniform acceleration. this lasts for 1.66 seconds after which it does not accelerate any more. how fast is it spinning at .87 seconds? alpha(i)=605 rad/s^2 B=1.89 Radius=2.03 cmHomework Equations...

hi there What is a Poincare' disc and why is the edges of disc represent infinity? thanks

Homework Statement I want to find a bijective function from [0,1] x [0,1] -> D, where D is the closed unit disc. Homework Equations The Attempt at a Solution I have been able to find two continuous surjective functions, but neither is injective. they are...

I understand that to find moment of force, we look at direction of force and perpendicular distance. In the diagram, O is the centre and pivot of the circular disc. Would the anticlockwise moment at A be (30N x 4m)? I'm not sure if this is true, cos the distance 4m is only AB. It does not...

Homework Statement 1. Find the volume of the solid generated by revolving the region bounded by the graphs of the equations about the indicated lines. y = \sqrt{x}, y = 0, x = 4 the line x = 62. Find the volume of the solid generated by revolving the region bounded by the graphs of the...