Disk Definition and 819 Threads

Homework Statement A force of magnitude 50N is applied at the bottom point Q of a disk of radius 8m that is pinned at P (leftŸmost point) See attached picture (a) Find the angle between the force and the vector from P to Q. (b) Find the magnitude of the applied torque. Homework Equations...

Hello! (Wave) I want to solve the Laplace equation on the unit disk, with boundary data $u(\theta)=\cos{\theta}$ on the unit circle $\{ r=1, 0 \leq \theta<2 \pi\}$. I also want to prove that little oscillations of the above boundary data give little oscillations of the corresponding solution of...

I apologize for the fact that this information is 2nd hand but a very intelligent and reliable friend tells me that in “Dark Matter and the Dinosaurs” by Lisa Randall she hypothesizes a disk of dark matter, which she calls “Double-Disk Dark Matter (DDDM)” that is superimposed over the center of...

Hi, I'm new to part design/mechanical engineering and I have the following question. I know it must be a very trivial question for most of you guys :) .. but I'm new to this. Blue: steel shaft, 5/8" diameter, connected to a motor Green: aluminum disk, 10" diameter, 1/2" thick, 3" hole Goal...

Homework Statement A solid disk of mass M and radius R is on a vertical shaft. The shaft is attached to a coil spring that exerts a linear restoring torque of magnitude Cθ, where θ is the angle measured from the static equilibrium position and C is a constant. Neglect the mass of the shaft and...

Homework Statement A solid uniform disk of mass 21.0 kg and radius 85.0 cm 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. 1- When the disk has moved a...

We apply Gauss's law to find electric field at a point due to chaged plane or plate. But what's wrong when applying to circular disk which can also be considered as a plane?

Hey all, I have a question that I am trying to figure out. It is more qualitative than anything, but I am concerned with the concepts that are involved in a scenario like this. Suppose we have a rotating disk with the plane of the disk perpendicular to the z-axis. Now we send a particle upward...

I'm using Windows 10 sometimes it is 100% full disk error, does anyone know how to fix it?

A new planet has been visualized in a protoplanetary disk around a star. It's the bright thing at about 4 o'clock. Star (PDS 70) is blocked out. Science magazine news article here.

Homework Statement A solid circular disk (m,R) translates with v1 and rotates with angular velocity w1=2v1/R, at t=0. Because of friction, pure rolling starts at time t. the coefficient of friction is C. Find velocity of center of disk at time t Homework Equations 1) for pure rolling v=Rw 2)...

The above picture shows the forces on a disk supported by a rope which is wound around it. The tension T is shown to be acting at the point where the rope loses contact with the disk. I think the reason for this is that the friction is assumed to be huge so that the tension in the rope also acts...

Homework Statement A solid disk of radius 23.4 cm and mass 1.45 kg is spinning at 43.1 radians per second. A solid cylinder of radius 12.1 cm and mass 3.33 kg is not spinning. The cylinder is dropped into the center of the spinning disk. After a short time friction has caused both objects to...

I tend to hold onto old technology that works. A few months ago, one of my Win 8 computers (ASUS laptop) developed a problem in which the OS has determined that 100% of the disk space is being utilized (according to the Task Manager). When I check the disk, it's less than 40%. For some...

Homework Statement 1. Homework Statement An uniform disk of mass m, thickness L and radius r is suspended from the ceiling by a wire. It is attached to the disk at a distance, d from the center of mass, so that it inclines at an angle A to the vertical. What is the moment of inertia of the...

Homework Statement Consider a half disk (of uniform density) with the flat end lying on the x-axis, symmetric about the y-axis (i.e. being cut into two quarters by the y-axis). Calculate the moments of inertia about each of the axes. Homework Equations $$I_{rr}=\sum_{i}m_ir_i^2$$ The Attempt...

Hello! I'm currently working on a project that will utilize the phenomena of eddy currents to apply a braking force to a rotating disk. Some background on this project: My team was tasked to create a physical therapy training device to train patients in wheelchair propulsion at resistances lower...

Homework Statement A disk of radius r and mass m is placed on an incline which makes an angle of 30 degree. The disk is suspended by a string attached to its center and a mass 3m is hung at the other end. The surface of incline is rough with the coefficient of static and kinetic friction...

Just to be clear, this is potentially a homewowrk problem I would assign. 1. Homework Statement This is a 2-D problem. You (mass m) are standing on the edge of a large disk (radius R, mass M). What happens when you jump off, with: a) The disk is on a frictionless surface, you jump radially...

Homework Statement We have a circle of radius 4 with center at the origin of a referential, and a circle hole in it of radius 1 and center at (-2,0). We're supposed to calculate the center of mass. 2.MY QUESTION. I know, by the usual formulas for calculating center of mass I get 2/15 as the x...

x = 2y - y2 x = y

Homework Statement When I have a disk with radius r then naturally the area is πr^2. Then I want to do this by calculus and my first step is simply taking πrdr. But the correct way is to take 2πrdr. To me this is really confusing, because I would never take 2πr dr (circumference x width)...

Homework Statement Hoop and disk with uniform mass distribution have the same radius but the total masses are not known. They both roll down ramp without slipping, reaching the bottom in the same time. What can you deduce about the relative masses? 1) disk is heavier, twice the mass of loop 2)...

I have made some editions blindly to my SD card. Now the PC cannot perceive the disk. I cannot see the disk under my computer but can see under device manager. What's the matter? What is the reason? Thank you.

Homework Statement A bug crawls outward from the center of a compact disc spinning at 210 revolutions per minute. The coefficient of static friction between the bug's sticky feet and the disc surface is 1.1. Homework Equations (static friction)(Gravity) = (centripetal force) This may be wrong...

Hello. Is it possible to create logical partitions for an external storage such as an SD Card? When I take a back up, I format the disk instead of deleting the old data because deletion takes too much time compared to formatting. Then I do a copy-and-paste new data to the disk evacuated from old...

When we cannot safely remove our usb memories and disks what are the other options? Sometimes we cannot safely remove them and take a notification. According to that notification a program is using the drive so we cannot remove it at that moment. Do you know what the error code for this...

Homework Statement When a disk rolls in a surface whitout slip, the velocity of the disk's edge (where it contacts the surface) is zero with respect the surface and the friction force is less than the maximum allowable of Us.N, where Us is the coefficient of static friction and N is the normal...

[Moderator's Note: Thread title changed to better reflect the problem statement] Homework Statement A body of mass m is on a disk of mass M=2m and radius R, initially static and free to spin around its center. The mass mm goes around a trajectory described in the image below with constant...

Homework Statement The problem is to figure out what acceleration is needed relative to a rotating disk to remain in the same spot(meaning to not rotate with the disk). Homework Equations a=wr^2 The Attempt at a Solution I thought that since the Person remaining stationary would be rotating...

Homework Statement A disk of radius R has an initial mass M. Then a hole of radius (1/4) is drilled, with its edge at the disk center. Find the new rotational inertia about the central axis. Hint: Find the rotational inertia of the missing piece, and subtract it from that of the whole disk...

Homework Statement [/B] A uniform solid disk of radius R is set into rotation with an angular speed ωi about an axis through its center. While still rotating at this speed, the disk is placed into contact with a horizontal surface and immediately released as shown in figure below (a) What is...

Hello everyone! I was wanting to know if something like this was possible. I read (Wikipedia) that the moment a cylinder will burst is when the hoop stress is equal to the cylinder's tensile strength. It also appears that the thickness of the material doesn't matter. I don't see Young's...

There are lots of videos on youtube etc showing Euler's disks. Why do we hear that periodic clattering sound? If it's a uniform rolling motion we would expect a smoother sort of whirring sound. (Like a monocycle running along a tight circle, maybe). What determines the frequency of the clatter?

Homework Statement The dropped disk rolls down with acceleration of centre of mass. The disks are identical, find accleartion of cm in terms of angular acceleration Homework Equations [/B] a = r*alphaThe Attempt at a Solution I don't know where to begin, I think the alphas should be equal...

I was studying about Accretion disks and found some difficulties regarding some concepts. My questions are 1. For an accretion disk, ## v_r<<c_s ## Why? 2. The conservation of mass equation is derived as, The mass in an annulus of radius ##\Delta r## is ##2\pi r \Delta r\Sigma ## and it is...

Suppose we have a spinning disk with a very fast spin, an observer in the center, and an observer on the edge. Suppose that the observer on the edge measures the circumference of the spinning disk. (1) Now, the observer on the edge at a given instant will be moving at a faster speed than the...

Homework Statement I have a particle of mass m. The particle is moving in direction of axis z because of the gravitational force of a homogeneous circular disk of mass M and radius a. There is a formula for gravitational force of the disk on the picture. Task: 1) Find the formula of...

Homework Statement There's a pendulum with mass m and longitude L strapped to a disk with radius R that rotates with an angular velocity ω. Calculate the angle that the pendulum is shifted (Φ) depending on ω. You are given m, L, R, ω, g. Calculate Φ depending on ω. Little drawing (with my...

Say I have a disk in ##R^2##. How would I know if it is compact? I mean, if the disk has no boundary, then we can have a limit that is outside the set. On the other hand, a disk with a boundary contains all limit points. But this seems unsatisfactory as for the open disk, we are assuming that...

In the following diagram, a frictionless disc is supported by a massless string. This problem was given by the author of a book, and a solution was given to some questions that were asked about this diagram. One thing the author said in one of the solutions, was that the tension in the string...

Homework Statement A very thin disk of mass m and radius R rolls without slipping along a horizontal plane. The disk is constrained to remain vertical. Let ψ be the angle between the plane of the disk and the x-axis of a fixed frame and θ be the angle measuring spinning of the disk about its...

Homework Statement A disk of radius ##R## has a cylindrical hollow that goes through it crossing its center ##O##. The disk rotates around its central axis with constant angular speed ##\vec{\omega}##. A little ball of mass ##m## and with the same radius of the hollow, is at a distance ##R_0##...

0 down vote favorite There is a lot of material discussing the rotational speed of the magnetic disk in HDD but not about the rotational speed of actuator arm. What are the typical actuation speeds of the actuator in HDD? This information will be used in the design of a fast shutter system...

Homework Statement Given a non magnetic rectangular plate with dimensions: L & B. The plate is of uniform density and thickness.There are 2 points equidistant from the center of the rectangular plate along the line at B/2. Both of these pivot points have 2 disks of radius R and mass M that are...

i am stuck on question 9 can anyone help me out. thanks

Homework Statement Attached. Homework Equations Tangenital acceleration=r*alpha 3. The Attempt at a Solution I thought it was just simply r*alpha=2*20=40 (choice A), but the answer key says choice B. I'm not really sure where I could have went wrong or its possible that there is a mistake...

Homework Statement A horizontal plywood disk with mass 6.90 kg and diameter 1.14 m pivots on frictionless bearings about a vertical axis through its center. You attach a circular model-railroad track of negligible mass and average diameter 1.04 m to the disk. A 1.40 −kg , battery-driven model...

Homework Statement A metal disc of radius R rotates with a constant velocity ω about its axis. FInd the potential difference between the centre and the rim of the disc if: a)the external magnetic field is absent b)the external magnetic field of induction B is directed perpendicular to the disc...

I've posted this here because I think it might be related to the absoluteness of acceleration and rotation. I've been educating myself on the Faraday Disk and was very surprised by one aspect of it. If we have a solid metal disk mounted on a shaft with two electrical brushes contacting the...