# 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. ### Are the Force Equations for Rotational Motion Accurate?

Writing force equations for block ##m## : $$T-mr\omega^2=m\ddot{r}$$ and for block ##M## : $$Mg-T=M\ddot{r}$$ I think there are mistakes in my equations as they are leading to nowhere and morever i think force methods are really risky in this regard . It would be better to write the total energy...
2. ### Rigid Body Problem Involving a Tilted Rotating Disc

Using these equations, I find L=0.02Nms, I=0.02Kgm^2 and KE=10mJ However, i don't think that this is the right method here.
3. ### Acrylic (PMMA) rotating disc tensile strength calculation

Hey folks, I've been looking around but can't piece this together as there are more than one equation and variable to take into account. My situation - I have a pmma material disc on an axis , the center hole (axis hole) is 20mm wide so a radius of 10mm, while the outer edge is at a radius of...
4. ### Efficient hit detection on a shot plate with piezo disc

Hello to all, I wish to detect the hit of a airsoft pellet on a shot plate with an ESP32 board. to do this I have basically two options: Either, detect the signal as digital (hit / missed) or detect the signal as analog signal with a piezo disks. The analog signal will have more information...
5. ### 2 Cords affixed at different points are wrapped on a disc

The hint says the following: "Since the cords are inextensible, every particle of a cord must be in circular motion about the point where it is affixed to the ceiling. Therefore, the velocities of the points where the cords are leaving the disc are perpendicular to the string" Due to the fact...
6. ### Conditions inside a protoplanetary disc

Summary:: Conditions inside a protoplanetary disc. I have just finished writing a fictional story that takes place inside a protoplanetary disc. Now I think I should determine how realistic it is. My question -- Somewhere in a typical PP disc, the gas pressure would be in the range of one...
7. ### I Disc of quiet and active Proxima

The radius of Proxima is quoted as 0,1542 solar. The distance of Proxima b is quoted as 0,04857 AU. It follows that the angular size of Proxima from b is 3,175 times angular size of Sun from Earth, plus correction to small angle approximation. Since Sun averages 32 minutes, Proxima is about 102...
8. ### I Solving for Angular Velocity After a Disc Collision

Hello to everyone, first of all shame on me I has to ask and can not figure out it by myself... The problem is I am trying to code game where two homogenous discs with same mass and same diameter, no fricition due to gravitational forces, can collide. I can figure out the speed and direction...
9. ### How Does Torque Affect the Motion of a Disc Pulled Across a Table?

I started out by drawing a diagram: So I thought I would try torque with the axis of rotation in the center: ##T_1R = \frac{Mr^2}{2}\alpha## and given that ##T_1## is equal to ##F## in the positive direction. ##\alpha = 266.6 \frac{rad}{s^2}## Then knowing the relationship between angular...
10. ### Find the maximum KE of a charged Disc

To find the initial potential energy of the system we can assume the disc to be placed inside a hollow sphere of the same radius and ##\sigma##, the potential energy inside a charged hollow shell is: $$V = \frac{\sigma(4\pi R^2)}{4\pi \epsilon_0 R} = \frac{\sigma R}{\epsilon_0}$$ the potential...
11. ### Atmospheric pressure inside a protoplanetary disc

Summary:: Could there be a place in a newly forming protoplanetary disc where the gas pressure and temperature would be anywhere close to survivable? I am writing a fiction story that takes place there, and I want to know how far from reality this premise would be. When a protoplanetary disc...
12. ### Oscillations of a disc with a smaller disc removed (Feynman ex. 17.23)

A disc of radius ##a## has a smaller disc of radius ##a/2## removed. The resulting object has mass ##m##: The centre of mass ##G## is a distance ##h = \dfrac{\pi a^3 - \dfrac{3\pi a^3}{8} }{\dfrac{3\pi a^2}{4}} = \dfrac{5a}{6}## from the edge. The moment of inertia of the shape about the...
13. ### I How Does the Book's Formula for Angular Momentum Differ from Mine?

A disc initially has angular velocities as shown It's angular momentum along the y-axis initially is ##L_s## I tried to find its angular momentum and ended up with this:##L=I_{x} \omega_{x}+I_{y} w_{y}+I_{z} z_{z}##The z component of angular momentum is thus ##L_{z}=I_{z} \omega_{z}## However...
14. ### I Trying to rotate a disc about two perpendicular axes

I've a disc which can rotate freely about two perpendicular axis (fixed to the body) If I simultaneous try to rotate it about the two axis, what will happen?
15. ### Moment of inertia of a disc using rods as differential elements

I know there are more convenient differential elements that can be chosen to compute the moment of inertia of a disc(like rings). the mass of the differential element: $$dm = (M/\pi R^2) (dA) = (M/ \pi R^2) (2\sqrt{R^2 - y^2})(dy)$$ the moment of inertia of a rod through its COM is...
16. E

### Observation about the rotation of a disc

Someone that I tutor asked a simple but pretty good question today which I thought I'd share the answer to. In a tidied up form: a disc with centre at the origin and central axis parallel to a unit vector ##\mathbf{n}## in the ##xy## plane rotates with a constant angular velocity...
17. ### Terminal angular velocity of Disc in magnetic field

Torque appiled by smaller disc = mga emf of disc due to B = Bwr2/2 Current I = Bwr2/2R force = IBr = Bwr3/2r torque = rF = Bwr4/2r mga = Bwr4/2r
18. ### Elastic collision of particle and rotating disc

Consider the system of the mass and uniform disc. Since no external forces act on the system, the angular momentum will be conserved. For elastic collision, the kinetic energy of the system stays constant.Measuring angular momentum from the hinge: ##\vec L_i = Rmv_0 \space\hat i + I \omega_0...
19. ### Thin disc with high thermal conductivity

I've tried to explicitly solve the Fourier's equation in cylindrical coordinates but I'm getting some messy integrals which cannot be solved analytically. Additionally my instructor said that there's a neat trick for this problem and it's possible to obtain the answer in a rather elementary...
20. ### B Accuracy of a smith's crafted metal disc

The area of a circular disc with radius ##r## is ##A=\pi r^2\;\mbox{cm}^2##. A smith must make a circular metal disc of ##400\pi\;\mbox{cm}^2## with an accuracy of ##\pm{5}\;\mbox{cm}^2##. Which accuracy range must have a ##20\;\mbox{cm}## disc? Answer The metal worker wants to obtain ##|\pi...
21. ### To find the angular momentum of a disc

I was first wondering wether we can solve this question by applying conservation or energy or not but after googling it I found that we can't apply conservation of energy since there will be some energy lost in this case. I don't know how this energy is getting lost. My second doubt was if we...
22. ### How can I find the velocity of a point on a disk rotating in a disc?

From a freebody analysis I got, $$\vec{r} \times \vec{F} = |r| |F| \sin( 90 - \theta) = (R-r) mg \cos \theta$$ and, this is equal to $$I \alpha_1$$ where the alpha_1 is the angular acceleration of center of mass of small circle around big one, $$I \alpha = (R-r) mg \cos \theta$$ Now...
23. ### Angular momentum of a rotating disc

"A smooth horizontal disc rotates with a constant angular velocity ω about a stationary vertical axis passing through its centre, the point O. At a moment t=0 a disc is set in motion from that point with velocity v0. Find the angular momentum M(t) of the disc relative to the point O in the...
24. ### Prop disc thrust uniformity in turns vs wing position

I would like to know what is the current consensus on the effect of the position of the wing relative to a tractive propeller disc's uniformity of thrust (the focus configuration would be WWII fighters).
25. ### MHB Physics 12u - Two masses Spinning on a disc

A penny of mass 3.10 g rests on a small 20.0-g block supported by a spinning disk. The block is sitting at the edge of the disc at a radius of 12 cm. If the coefficient of friction between block and disk are 0.750 (static) and 0.640 (kinetic) while those for the penny and block are 0.450...
26. ### Revolving disc in a magnetic field

I know that there is a known equation to calculate the magnetic field strength of a rotating disc which I have made use of in here Do you agree that revs per minute of the disc turns out to be 9337 rpm? Thanks for any help! Much appreciated
27. ### Automotive Placement of disc brake calipers for best performance

I thought that there was a standard placement for disc brake calipers on the front and back wheel assemblies for high-performance sports cars. I thought that I usually saw them placed at the back of the front wheels and the front of the rear wheels, but lately I've seen the opposite and other...
28. ### Rigid body motion - thin disc

Why is the gravitational potential energy of the chain's center of mass equal to the total kinetic energy of the disc after it was fully wrapped? My first thought was to write ##E_{0}=(M/2+M)g∗2πR=E_{f}= Ep## (from the chain) ##+Ec## (from the disc). Instead he wrote ## mg \frac{l}{2} ## = ##...
29. ### Particle moving in a rotating disc

Well, I tried plugging the data in the formula. I know that ##\vec a_b = 0; \vec \omega=3 rad/s ; \vec r## can be calculated using trigonometry. Then I also know that ##v_{relx}= 10 cm/s##, ##a_{relx}=15 cm/s^2##, ##\vec {\dot{\omega}}=-10 rad/s^2##. But how do I get ##v_{rely}## and...
30. ### Relative rotational motion on a disc

The first doubt that comes to my mind is "I have to determine the acceleration with respect to what?", because the problem doesn't tell. Then, I have some problems when having to plug the data in the formula of acceleration. ##\vec a_B=0## because the origin isn't accelerated, ##\vec{\dot...
31. ### Making a copy of a KNOPPIX 5.0 disc that boots

I had a KNOPPIX 5.0 disc. I made a copy of the files on this disc, but I then damaged the disc. I have tried simply burning these files onto a dvd disc but it won't boot. Can I use the files that I saved to created a "bootable" KNOPPIX disc?
32. ### What is the angular velocity in the center of a rotating disc?

I have a disc. The center of the disc is its center of mass and the motion of the disc is purely rotational (no translation). What is the angular velocity in the center of the rotating disc?
33. ### Probability of hitting a rotating disc

There are two points of the smaller disck such that a line is tangent to the two discks and passes by that point. If the particle leaves of any point belongin to the arch that connects these two points, then it will hit the other disck. So I managed to calculate the value of this arch and divide...
34. ### B Curve Space-time from Spinning disc?

Please see attached illustration (from Discover September 2004. Einstein 100 years special issue). Is it correct that one key to Einstein's thinking is to analyze a spnning disk. That "Since the rim of the disk travels faster than the center of the disk, the theory of relativity states that the...
35. ### Potential energy of a shell and a disc, both covered uniformly with charge

Double integration maybe?? I calculated potential due to shell on plate's center but not on other points on it's surface.
36. ### MCNP6 Disc Source Setup: Troubleshoot 0 Counts

I am attempting to build a sodium iodide detector on MCNP. I am using a disc source and I have been trying to define it in terms of a cell that I placed underneath the detector. When I run it, I get 0's for my counts. This indicates to me that my source isn't hitting my detector. I keep...
37. ### How Do Mass and Windings Affect Disc Rotation Dynamics?

I am doing a project, but am struggling to find relationships of proportionality or formulae between my dependent variables (angular velocity, displacement, acceleration of the disc and kinetic energy of the system) and my independent variables (falling masses and then the number of winds) or...
38. ### What Forces Affect the Rotation of a Submerged Disc?

1. A 20-lbf disc with diameter 18" and thickness of 3" is held static while completely submerged in water. Upon release of a lock, the disc experiences a torque from a torsional spring that causes rotation about its center of mass along the x/y axis (think coin toss, not wheel). If the spring is...
39. ### How Do You Derive the Constraint Equation for a Disc Rolling Along a Parabola?

Homework Statement A disc of radius R rolls without slipping along the parabola y= ax2. Obtain the constrain equation Homework Equations Because there's no slipping, then: ##R d \theta = ds (1)## Where ##\theta ## is the angle between the line from the center of the disc to a fixed point...
40. ### What is the kinematics of a rolling disc on a tilted plane?

So the kinematics of the contact point of a disc rolling without slip in a Cartesian plane if fairly straightforward. The velocity for the contact point is just v = ω r ev where r is the wheel radius and ev the current direction vector of the wheel. However, say that you grab the plate and...
41. ### Elliptic functions, diff eq, why proof on open disc holds for C

Homework Statement Hi I am looking at this derivation of differential equation satisfied by ##\phi(z)##. To start with, I know that such a disc ##D## described in the derivation can always be found because earlier in the lecture notes we proved that their exists an ##inf=min \omega ## for...
42. ### Speed of a disc after a collision

Homework Statement I understand that if the change in impulse is 0.25, that because disc B is originally stationary the momentum disc B will have is equal to the impulse. My question is how do we do this in terms of change in momentum? Homework Equations ΔP = Pf - Pi P = mv The Attempt at a...
43. ### Conservation of Angular Momentum on a rotating disc

I have a disc that is rotating due to air being blown at its outer radius. The incoming relative velocity of the air is high, therefore the effect of friction supersedes the effect of conservation of angular momentum. The tangential portion of this velocity decreases due to the friction as it...
44. ### Faraday disc: different configuration question

I started thinking about this again because it never really left my mind. Now we know the three different scenarios for the Faraday homopolar disc,1) The disc rotates while magnet and brushes with the circuit they connect stay stationary in the laboratory reference frame = result , current...
45. ### Vector torque problem: Force applied to a disc

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 (leftmost 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...
46. ### I Random set of N points in a unit disc, what is the average nearest distance

Pick a random set of N points from the unit disc. Calculate the distance between all pairs of points and call the smallest value r. Do this calculation for many such sets. Please give me a hint how to estimate what the average value of r is. I guess a computer program could quickly come up with...
47. ### Rotation of Rigid Bodies: Rotating stick with disc on top

Homework Statement [/B] A thin cylindrical rod with the length of L = 24.0 cm and the mass m = 1.20 kg has a cylindrical disc attached to the other end as shown by the figure. The cylindrical disc has the radius R = 8.00 cm and the mass M 2.00 kg. The arrangement is originally straight up...
48. ### I Comparison of movement of Disc and Hoop

A disc and a hoop (ring) both of same mass and radius roll down an inclined plane of height "h". It is well known the disc has great velocity than that of the hoop at the bottom. I am fixed in the situation after they start rolling horizontally. Which will go farther? If the surface is...
49. ### I Accretion disc poloidal magnetic field, right or left hand rule?

If your fingers of one hand curl around the axis of rotation of the accretion disc of a massive black hole and your fingers point in the direction of the flow is the direction of the central twisted poloidal magnetic field given by a right hand rule, a left hand rule, no rule? Is there a simple...
50. ### A Holomorphic function on a disc

I want to solve the following problem: Suppose B=B(0,R) be a ball in C^n, n>1. Let f be holomorphic in B and continuous on B closure. If f(a)=0 for some a in B, show that there is p in boundary of B such that f(p)=0. I assumed f(p) is non zero for every point p in boundary B and create...