What is Disc: Definition and 396 Discussions

DISC is a behaviour self-assessment tool originally based on the 1928 DISC emotional and behavioural theory of psychologist William Moulton Marston, which centred on four personality traits: Dominance, Influence, Steadiness, and Compliance. This theory was then developed into a behavioural assessment tool by industrial psychologist Walter Vernon Clarke. Personality expert and researcher, Merrick Rosenberg, notably innovated on the contemporary application of the DISC model as it applies to team development, interpersonal relationships, and American presidential campaigns. DISC has not been scientifically evaluated.

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  1. D

    Accumulation point unit disc

    Let f(z) = \prod\limits_{n = 1}^{\infty}(1 - nz^n) Prove that each point on the unit circle is an accumulation point of zeros of f So we have that z = \sqrt[n]{1/n} . Now where do I go from here? Probably should note that this is a Weierstrass Product.
  2. V

    Electric field due to a uniformly charged disc

    At the end of the derivation, it is given The electric fiel due to elementary ring at the point P is dE = [2∏rσdrx]/[4∏epsilon zero (x^2 +r^2)^(3/2) ] To find the total E due to disc is given by ∏σx/4∏ε∫(2rdr)/(x2 + r2)3/2 I am stuck with the calculus done here to arrive at the...
  3. L

    Understanding Tangent Vectors for Discs: Deciphering (1 -1 0)T

    Homework Statement I do not understand how the vector (1 -1 0)T represents the axis tangent to the disk at Q. The Attempt at a Solution Tried thinking in terms of simple vector addition, but just got another vector in the radial direction... I mean, (1 -1 0)T is parallel to a tangent...
  4. E

    How Does a Rolling Cylinder Affect the Acceleration of a Slab?

    A uniform solid cylinder of mass M and radius R is at rest on a slab of mass m, which in turn rests on a horizontal, frictionless table. If a horizontal force F is applied to the slab, it accelerates and the cylinder rolls without slipping. Find the acceleration of the slab in terms of M, R, and...
  5. J

    Electric field of a charged disc

    ... with constant charge density σ = Q/((pi)a^2) The Electric field is, after some calculation, is given by E_p below: z is the z-axis, and a is the radius of the disc. Now for the questions at the bottom of the page, here are my thoughts: σ is independent of a because as a->2a, Q->4Q, and...
  6. D

    Analytic mapping of unit disc onto itself with two fixed pts.

    Homework Statement let f(z) be a 1-1 analytic mapping of unit disc |z|<1 onto itself with two fixed points in |z|<1 Show that f(z)=z Homework Equations none The Attempt at a Solution I'm thinking there has to be a theorem or something that I am missing for this.. But I'm not...
  7. L

    Why can't holomorphic functions be extended to a closed disc?

    If u is harmonic function defined on (say) the open unit disc, then it can be continuously extended to the closed unit disc in such a way that it matches any continuous function f(θ) on unit circle, i.e. the boundary of the disc. But my understanding is the same cannot be said of holomorphic...
  8. D

    MHB Example about uhp iso to unit disc

    I am trying to understand this example: Let H be the upper half plane. The map $$ f:z\mapsto\frac{z - i}{z + i} $$ is an isomorphism of H with the unit disc. proof: Let $w=f(z)$ and $z=x+yi$. Then $$ f(z) = \frac{x + (y-1)i}{x+(y+1)i}. $$ Since $z\in H$, $y>0$, it follows that...
  9. D

    MHB Analytic is UHP to unit disc

    Prove that the most general analytic isomorphism of the open upper half plane, $\mathcal{H}$, onto the open unit disc is of the form $$ T(z) = e^{i\varphi}\frac{z - a}{z - \bar{z}} $$ for some $\varphi\in\mathbb{R}$ and some $a\in\mathbb{C}$ with $\text{Im}(a) > 0$ I need some guidance here...
  10. L

    Kinetic energy of a rotating disc

    if KE=1/2mv^2 and you have a circular object rotating, with it's mass uniformly distributed through the object (ie each part of the disc weighs the same) then obviously certain parts of the disc will be moving faster than others. therefore closer to the middle of the disc, you have more KE...
  11. G

    Rolling problem - disc on disc

    This is a typical case of friction wheels where one wheel drives the other...what I want to know is how can we model the problem when slipping occurs ... also in case of no slipping how will the free body diagrams and forces be balanced on both disc?
  12. A

    Could CDs (Compact Disc) cause fire if I hang them outside the windows?

    Hi, I live in 6th floor of an apartment. To prevent birds from pooping beside my window, I hang some unlabeled CDs along a string outside the window. The window is facing east, and people start complaining about it, that it might cause fire. I wonder if that is even possible? I personally do...
  13. J

    Torque on the Accretion disc

    http://www.maths.qmul.ac.uk/~rpn/ASTM735/lecture3.pdf The diagram on page 26 is the accretion disc. The torque acting on the inner edge of the ring (the one that has a thickness of dR in the diagram) is RFin = -2\piR3\nuƩ\frac{dΩ}{dR} The torque acting on the outer edge of the...
  14. D

    MHB Dirichlet Problem for Laplace's Equation Outside of a Disc

    The Poisson Integral Formula is a representation of the bounded solution of the Dirichlet problem for Laplace's equation in the interior of the disc. Derive the corresponding formula for the Dirichlet problem in the exterior of the disc, again assuming that the solution is bounded.So we derived...
  15. D

    MHB Analytic Functions on the Unit Disc

    Analytic in the unit disc $z^7$ yes $|z|$ no $\frac{1}{z}$ yes Correct?
  16. B

    Motion equations of a disc rotating freely around its center (3d)

    Homework Statement The system is made of a disc the center of which is pinned to the origin (so the disc cannot translate), and some weights that can be stuck on the disc to make it tilt (weights do not translate on the disc) (see images attached). There is no friction whatsoever. The only...
  17. B

    Motion equations of a disc rotating freely around its center (3d)

    The system is made of a disc the center of which is pinned to the origin (so the disc cannot translate), and some weights that can be stuck on the disc to make it tilt (weights do not translate on the disc) (see images attached). There is no friction whatsoever. The only force is gravitational...
  18. G

    Fluid mechanics calculating force needed to lift submerged disc

    Homework Statement The problem: There is an illustration and the question is to find the force F to lift a concrete block gate if the the concrete weighs 160 lb/ft3. The block is 3' in diameter and 1' thick. It is in a tank of fresh water 15 ft down. the specific weight of the fresh water...
  19. J

    Hydrostatic Equilibrium in an Accretion Disc

    This is regarding an accretion disc orbiting a star. In the z (vertical) direction there is a hydrostatic equilibrium. \frac{1}{ρ}\frac{∂P}{∂z} = -\frac{GMz}{(R^{2} + z^{2})^{3/2}} The right hand side of the expression is the Gravitational potential energy and the left side is the pressure...
  20. S

    MHB Holomorphic function and an open disc

    Now the function f is holomorphic in an open disc U and that Re( f ) is constant in U. I'm trying to show that 1)f must be constant in U. 2) the essential property of the disc U that it used here 3) an example of an open set U for which the conclusion fails. Let f=u+vi where u is a...
  21. S

    Help with a unit disc property for a holomorphic function

    Homework Statement Suppose that f is holomorphic in an open disc U and that Re(f) is constant in U. I have to show that f must be constant in U. Also what is the essential property of the disc U that it used here? Give an example of an open set U for which the conclusion fails.Homework...
  22. B

    Finding Frequency of an Oscillating Disc with a Hole

    Homework Statement A circular disk with a rectangular hole has a radius of 0.600 m and mass of 0.390 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 = 2.60E-1 kgm2. Its center of mass is located at a distance of s=0.120 m...
  23. A

    Why does an aluminum disc rotate in an induction meter?

    In an induction meter two coils induce two eddy currents in same disc.It is said that the disc rotates due to the torque produced by the interaction of these currents with each other.How is that?I don't know the governing law.Can the torque be derived from the basic maxwell's equation?
  24. M

    Calculating horizontal force from disc magnet

    Homework Statement I want a box shaped robot to move on the ceiling. The robot sticks to the ceiling using magnets. I am attaching a picture. The red is a magnet. How do I calculate how much force is needed to move the robot horizontally? I know very little physics and I need to figure out how...
  25. dlgoff

    Remembering Capacitance Electronic Disc (CED)

    The TMC channel is showing "Close Encounters of the Third Kind" which brings back the memory of RCAs Capacitance Electronic Disc. Anyone remember these? http://upload.wikimedia.org/wikipedia/en/thumb/e/ed/Ced_cart2.jpg/670px-Ced_cart2.jpg The first "video disk" I ever purchased/watched was:
  26. B

    Find torque in disc brakes given normal force and coefficient of friction

    Homework Statement In the disc brakes that slow down a car, a pair of brake pads squeezes a spinning rotor; friction between the pads and the rotor provides the torque that slows down the car. If the normal force that each pad exerts on a rotor is 85 N, and the coefficient of friction is 0.62...
  27. A

    Hollow Metal disc loading - the needed thickness of the disc?

    Hi, how to calculate the limit of load you can place on the top of the circular plate with a quite big circular hole in it (OD 10 cm, ID 5 cm)? the question is how to calculate the thickness needed to bear 1 kg which is spread on the whole area (1 kg heavy object with the same shape as the...
  28. G

    Laurent and Taylor series in the unit disc

    Homework Statement Let f(z) be a function that is analytic for all |z|≤1, with the exception of z_0, which lies on the circle |z|=1. f(z) has a first order pole at z_0. Letting Ʃ a_n z^n be the Maclaurin expansion of the function, prove that z_0 = lim_(n→∞) a_n/a_(n+1) Homework Equations...
  29. T

    Mouse falls on rotating disc, find the work it needs to go to the center of it

    Homework Statement mass of the mouse = 0.05 kg disc's radius = 0.2m disc's angular speed = 33 rev / min assume that the angular speed ω doesn't change Homework Equations tangential speed = ω * r The Attempt at a Solution well, what i did was: drew the vectors, one was the...
  30. S

    Does a ring contract faster than a disc?

    Household physics question: Before I left town for 3 weeks the lock on my apartment door was loose in its encasement. I had to hold it in place while turning the key or the inner disc would rotate uselessly inside the outer ring: http://scott-shepherd.com/share/forums/lock.jpg When I came...
  31. R

    Proof for moment of Inertia of thin disc

    Homework Statement Its actually not a homework , i am just curious about this I have disc with a hole in middle , R1 is inner radius , R2 is outer radius , Mass M is the disc's mass . Let density of disc uniform . I did it this way . - λ.dA=dm λ.pie.r.dr=dm as Area=pie.r^2...
  32. R

    Force Required to stop a Rotating Disc

    Homework Statement Essentially, I am trying to determine the force that must be applied to a rotating disc to that stop that disc from rotating in a certain time period. The disc is rotating at 5800 rpm, the disc has a radius of 5 inches, and a thickness of 0.087 inches. The disk is made...
  33. F

    Why is the thick disc hard to study?

    Homework Statement As said in the title, why is the thick disc of our galaxy hard to study? The attempt at a solution I thought at first it may have something to do with the fact that the thin disc is so populated with stars that the light coming from it may interfere when trying to...
  34. A

    Dynamics: disc released horizontally, with pin fixed to edge (rotation)

    Hi guys, I am really stumped by this 1st yr Dynamics question, and would appreciate any help on how to approach the question. Homework Statement Homework Equations Torque equations and Force equations Moment of inertia for disc rotating around centre: (mr^2)/2 After using parallel...
  35. B

    Calculating Electric Field Above a Disc of Charge

    Homework Statement The electric field, E a distance z above a circular loop of charge density lambda, radius r, in the x-y plane centred on the origin, is given by E(z)=[lambda z r] i(subscript z)/[2 epsilon0((z^2 + r^2)^(3/2))] a) using this, find the electric field, E, a distance z...
  36. D

    Thin disc above grounded plane

    Homework Statement A thin disk of radius R consists of a uniformly distributed total charge Q. The disk lies a distance D above a grounded perfectly conducting plane. The disk and the plane are parallel. Set the conducting plane in the x-y axis, and the z axis through the center of the disk...
  37. U

    Calculating the Elasticity of an Annular Disc Without Prior Information

    Hi, I have an annular disc that looks like the following: I need to get the elasticity of the material, since I don't have any information on it. Does anyone have any suggestions on how I can calculate the elasticity? Maybe I can get a force/displacement curve by bending the disc...
  38. P

    Too Complex for me - multiple torques on rotating disc

    Hi all... my first time here... I hope someone can help. I'm toying with a home project (in the early conceptual stage), and the attached picture shows "in general terms" what I'm trying to figure out. The outer 'wheel' rotates about its central axis, driven at that axis by a small motor...
  39. B

    Gravity at an arbitrary location near a disc

    Homework Statement calculate the gravity acceleration at an arbitrary location due to a disc of thickness h, radius r and density p Homework Equations g=Gm/r^2 The Attempt at a Solution define r in terms of the vector magnitude from the measurement point to some point on the...
  40. C

    Quick yes or no charged disc e field equation question

    Homework Statement the e field is given by (2*pi*k*omega)[1-(1+(R^2)/(z^2))^-.5] I was wondering if the capital R in that equation is the radius of the charged disk? And if so, why is it capitalized?
  41. T

    Collision of an expanding disc with another disc.

    Hi, Like a lot of people programming, I created a simplistic 2D collision engine. This engine handles the collisions of circles (I know I typed "disc" in the title, but I wanted to avoid replies like "circles don't really exist so they can't collide".) The simulation is friction-less, so...
  42. L

    Angular Velocity & Mass: Shaft Rotation & Disc Effects

    How does the angular velocity change with increase in the mass? For example : if there is a shaft rotating at 1500 Rpm , then if a disc of 5 kg is fastened , does the angular velocity of the disc will be same as 1500 RPM , and what happens to the RPM if the disc mass is 50Kg.
  43. R

    Dimensioning of big floating disc

    Is the following, ignoring that weight has been used as a force, correct? (excerpt from blog at http://floathaven.com/2011/07/the-solution-to-rising-waters-wednesday-blog/" )
  44. A

    Airy Disc Formula: Why Does it Include 1.22?

    Why Airy disc formula has 1.22 in front of it?Does it depend on aperture diameter?Thanks
  45. P

    Circular Motion of a horizontal disc Problem

    Hi :smile: A horizontal disc has a hole through its center. A string passes through the hole and connects a mass m on top of the disc to a bigger mass M that hangs below the disc. Initially, the smaller mass is rotating on the disc in a circle of radius r. What must the speed of m be such...
  46. D

    How much torque needed to turn a 1.2m disc

    Hi I a building an exhibit for a science museum and hoped I could get some help with the math that is puzzling us. We need to turn three discs that are 1.2m, 0.8 and 0.6m in diameter at a speed of roughly 60rpm. Because it is a musuem they need a clutch and at the minute we are looking at a...
  47. S

    Calculating the motion of a frisbee disc?

    I just got back from playing a round of Frisbee or Disc Golf at my local course and it got me thinking... assuming that there is no wind and standard pressure, would it be possible to predict the motion of the flying disc? to predict where it will land? it's flight path? so far I have...
  48. P

    Finding Electric Flux of a Disc of Radius r

    a disc of radius r we have to find electric flux at a point which is at a distance r from the centre i have used e=(sigma/2eo)(1-x/sqrt(r^2+x^2)) the area da=2pir*dr i know flux=closed integral (e.da) and x=r after that what should i do Reply With Quote
  49. U

    Moment of inertia of a spinning disc pendulum

    Homework Statement Find the moment of intertia of a pendulum, consisting of a disc free to spin attached to a rod that is hinged at one end. Homework Equations Moment of intertia of rod hinged at end = (1/3)Ml2 Moment of intertia of disc = (1/2)mR2 + ml2 The Attempt at a Solution...
  50. F

    Retarding force of eddy currents in a disc

    Homework Statement How to calculate braking force generated by eddy currents. If there is a disc of radius r with conductivity K, with a magnet located at a distance r-d from the center of the disc with a magnetic field B, what is the retarding force of the magnetic field created by the eddy...
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