Rotating Definition and 1000 Threads

Homework Statement Hello, I just started my summer class "Applied Linear Algebra I" Last math class of my under-grad and its been 1 year since I've last taken Calc3, so I'm trying my best to get back into the groove...anyways. Our first topic we are discussing in class is vectors. [1] This...

Homework Statement A ball of mass m and radius r starts off on top of a fixed ball of radius R. it rotates down without slipping. What's the ball's center of mass velocity as a function of θ. The angular velocity is ω. Homework Equations Moment of inertia: ##I=\frac{2}{5}mr^2## Potential...

It is known that 8000m/sec is the speed required for an object traveling parallel to the Earth's surface to orbit (i.e. so that the centripetal force counteracts the gravity force). I am now thinking to an object linked to an axis of rotation (e.g. with a 1m string) and rotating about that axis...

After the recent discussion here about the Sagnac effect** I wanted to see if there is any frequency shift if light is sent from one point on a rotating worldline to another a small distance away. It looks like this cannot happen because ##\gamma=dt/d\tau## is the same at every point on the...

Homework Statement .[/B] Given an infinitely long charged metal cylinder that is rotating with an angular velocity ##\omega## The charge density per unit length is ##\rho##. Find the magnetic field within the cylinder. I'm trying to solve this problem by using Ampere's Law. But couldn't reach...

I was given a problem recently that I had to solve and I haven't been able to get a fully satisfactory conceptual grasp of a certain aspect of it. Consider the slowly rotating Kerr solution ##ds^2 = -\alpha^2 dt^2 + \alpha^{-2}dr^2 + r^2d\Omega^2 - \frac{4Ma}{r}\sin^2\theta dt d\phi + O(a^2)##...

Hello - I've been trying to solve this for a little while, and feel I may not understand some core concepts required to solve the problem. If you have any ideas, please let me know! I would very much like to discuss how to solve this. I am trying to calculate the bend moment from a rotating...

Homework Statement A shaft 2 m long rotates at 1500 revs min–1 between bearings as shown in FIGURE 2. The bearings experience forces of 5 kN and 3 kN acting in the same plane as shown. A single mass is to be used to balance the shaft, so that the reactions are zero. The mass is to be placed at...

Homework Statement 'Consider the system consisting of a bead of mass m sliding on a smooth circular wire hoop of mass 2m and radius R in a vertical plane, and the vertical plane containing the hoop is free to rotate about the vertical axis. Determine all relative equilibria of the bead.'...

A particle is attached to an inextensible string. The other end of the string is attached to the centre of a rotating rough disc. The string is shorter than the radius of the disc so the particle remains on the disc and moves in uniform circular motion. I don't remember the quantities but the...

Homework Statement [/B] In the overhead view of the figure, a long uniform rod of mass m = 0.24 kg is free to rotate in a horizontal plane about a vertical axis through its center. A spring with force constant 240 N/m is connected horizontally between one end of the rod and a fixed wall. When...

Homework Statement A solid sphere of mass m and radius a can rotate freely about a point A on its surface. The sphere is held initially at rest with the line OA through A and the centre of the sphere O horizontal and is released under gravity. Find the angular velocity of the system when OA...

Homework Statement If there is a horizontal tube rotating on axis in horizontal plane. it is filled with an ideal gas , So which end will the pressure be higher ? the end on axis?? or the free end Homework Equations P.A= m .w^2 .r The Attempt at a Solution i think the free end should have...

Rotate an array hi everyone I'm hoping someone maybe able to help me/ point me in the right direction with the rotation of data from an array. I'll try to keep it short but my maths skills are seriously not good due to my old age and inexperience. I maybe approaching it from the wrong angle and...

Hello everyone, I am new to this forum, and here is my first question. I need some help in a particular case regarding torques. Most of the examples given anywhere on the web and books have rotations which are affected directly by gravity like pulleys and such, but, what if I want to calculate...

Homework Statement Homework Equations Read below The Attempt at a Solution A) D. As the mass of the students gets further away from the axis of rotation, the rate slows down (remember the skater with arms out). B) T. No explanation currently... C) ? D) T. The students exert a force on...

Homework Statement A slotted link AC is is driven by the peg P connected to a rotating disk. Point A is fixed. Determine the link's angular velocity, \omega_{ac} and acceleration, \alpha_{ac} when the angular velocity and acceleration are \omega and \alpha , respectively. \omega = 6...

How do we find out the tension in a rotating ring of density ρ, radius r which is rotating with an angular velocity of ω and area of cross section A? And how do we know that this tension would be constant throughout the ring?

Hello Guys, I have a disk of diameter of 150mm and thickness of 10mm which is rotating at the constant speed of 100rpm. The disk is inside water which is approximately 4-5 cm below the surface. Disk is horizontal (parallel to the water surface). Disk is attached with the shaft of the motor. At...

Homework Statement [/B] Find the Cartesian coordinates (x, y, z) of a fixed reference frame expressed in terms of the coordinates (x', y' , z) of a rotating frame, which rotates with the horizontal rod HR. Choose the x' -axis to point along the horizontal rod in the direction OA. Use this to...

Homework Statement A uniform plate of mass M stays horizontally and symmetrically on two wheels rotating in opposite directions. The separation between the wheels is L. The friction coefficient between each wheel and the plate is N. Find the time period of oscillation of the plate if it is...

Homework Statement http://imgur.com/jcZRQdu Homework EquationsThe Attempt at a Solution So I know how to solve this with conservation of energy, but I can't seem to get the correct answer using kinematic equations. τnet = Iα = (MR2*(a/R)) -Tension = MRa Fnet = ma w-Tension = ma -Tension =...

Homework Statement http://postimg.org/image/5o9kcuj57/ I do not understand what the vectors W and V represent Homework EquationsThe Attempt at a Solution I know U is the tip speed velocity but I don't know about the other two

Homework Statement The 3.2kg , 37-cm-diameter disk in the figure is spinning at 350 rpm . How much friction force must the brake apply to the rim to bring the disk to a halt in 2.4s? Homework Equations F = m * a I = (1/2) * mass * radius2 (I probably need to use this but I can't figure...

Homework Statement A long light inflexible rod is free to rotate in a vertical plane about a fixed point O. A particle of mass m is fixed to the rod at a point P a distance ℓ from O. A second particle of mass m is free to move along the rod, and is attracted to the point O by an elastic force...

Homework Statement Consider a uniform rod of mass 12 kg and length l.0 m. At its end, the rod is attached to a fixed, friction-free pivot. Initially the rod is balanced vertically above the pivot and begins to fall (from rest) as shown in the diagram. Determine, a. the angular acceleration of...

I am looking for a way to calculate the torque, hence the viscous damping coefficient per T = c*w, acting on a rotating metal disk in an oil sump. How can I go about it? Thanks! PS. I am not a ME so please forgive my ignorance.

Homework Statement A disc is on a desk, with a rotation point underneath. A string is wrapped around it, and the end of the string has a mass attached to it. The string end is put over a pulley, and when the mass is dropped it causes the disc to rotate. We are given mass of the disc (80g)...

Hello, There is an omni-directional and coherent light source rotating at the frequency of EM waves. If you think of the wave model, there will be nothing unexpected that you can imagine the space is rotating around the source. However, if it is quantized I can't tell what happens since photons...

I was wondering what might happen If we for instant, Rotated a ball around an axis in a vacuum chamber. First, If the initial speed was 20m/s would it remain like that forever, hypotheticaly saying No friction exists and that Air Resistance does not exist as the Ball rotates in vacuum. Also...

My question is about comparing the time dilation of a clock on a spinning disk versus a clock in the vicinity of a massive object. It seems there should be a connection between the two, because of the equivalence principle, but I'm missing something because I don't quite get the answer I would...

Homework Statement A cylinder contains an ideal gas and rotates at angular speed w. Find the probability that a molecule is at radial position r from the axis of the cylinder. Homework Equations Boltzmann distribution, P(E)∝Ω(E)exp(-E/kT) where Ω(E) describes the degeneracy of the energy level...

A horizontally oriented tube is rotating with angular velocity ω about one end of the tube which is open. The tube has ideal liquid filled inside it as shown in the attachment. Why does there have to be a pressure difference between two points in the ideal liquid at the same horizontal level...

Consider a rod AB rotating about one of it's end A with angular velocity w. Now angular velocity of each point of the rod is same i.e. w. But if we have to find the relative angular velocity of the end B w.r.t. mid point of rod, what it will be? Will it be zero because, w-w=0 or first we...

Homework Statement A drum of mass MA and radius a rotates freely with initial angular velocity ωA(0). A second drum with mass MB and radius b > a is mounted on the same axis and is at rest, although it is free to rotate. A thin layer of sand with mass Ms is distributed on the inner surface of...

Here , I want to clear about the cause of electromagnetic or interaction torque.>! I am confused in two things.. I read that the flux produced by stator coil & rotor coil interacts , the interaction give rise to electromagnetic torque.. But how this interaction produce torque..?? Is it like...

Homework Statement [/B] A particle of mass m slides (both sideways and radially) on a smooth frictionless horizontal table. It is attached to a cord that is being pulled downwards at a prescribed constant speed v by a force T (T may be varying) Use F=ma in polar coordinates to derive an...

If you had a rotating object like a tire or barrel that you wanted to distribute compressed air to while it's rotating, what would some ways to do it? One way I'm thinking is just a tight seal at the axis, but then there would be a lot of friction. Any other ideas??

Homework Statement So I am calculating torque and power for a disk of radius 0.5 m that is subjected to a force of 50 N at its periphery and is rotating at angular velocity of 100 rad/s. Find torque and power.[/B]Homework Equations Torque= radius x Force = 0.5m *50N = 25Nm Power= dW/dt=...

Hello, first post! I'd apreciate some help on finding out the calculus for knowing the motor's torque needed for mantaining 2 vertical disks ø46cm, 30kg each at 300rpm, taking into acount 3 generic bearings friction that hypotetically is 0.5Nm friction torque I'm having some trouble trying to...

Homework Statement Homework Equations τ = μ (du/dy) The Attempt at a Solution For part B) dM = τr dA τ = μ (rΩ/Δr) ∫ (μrΩr2πr / Δr)dr = μR4πΩ / 2Δr pretty sure that's correct. I'm confused for part A though. I want to set it up as dM = τR dA = τR (2πRdL) and τ = μ (RΩ/L)...

Homework Statement I am trying to answer the following question: Among the animals that appear in the zoo of the Universe there are black holes and neutron stars. The mass of each of these is often the order of the mass of the Sun. The radius of a neutron star is about 10 km and a certain...

I have recently come across the notion that Kerr metric describes the spacetime outside a rotating black hole but not outside a rotating (electrically neutral) star. Unlike Schwarzschild metric, which works both for non-rotating spherically symetric black hole without charge as well as any other...

Hello, I have a few questions about rotation and relative motion. Suppose we transport the proverbial spinning ice skater used to demonstrate conservation of angular momentum to beginning physics students to a universe with only her and two planets. She is now spinning in deep space...

I read that a non rotating planet like Lubricon VI does not have equator because it does not rotate. So why only rotating planets have equator?

how do we know which system of coordinates to use whether (polar) or (tangential and normal) in case of a rotating system ??

Homework Statement A uniform rod of mass M and length L can rotate around point P which is at position x from one end of the rod as shown in the figure. The rod is gently placed on a rough horizontal surface that has a friction coefficient μ. and at t=0 starts rotating with angular velocity...

Homework Statement I'm trying to understand an example from my textbook about angular momentum. This is the example given: For the part in red: I don't understand where the cosine theta term came from. When you're calculating the magnitudes of torques, don't you just use FRsin(theta)? If...

Homework Statement ##M\ddot{y} + k_{eq}y = me\omega^2\sin(\omega t)## What is ##m##? Homework EquationsThe Attempt at a Solution In the ODE above, ##M## is the total mass of the problem, correct? For instance, if we had a cantilever beam, ##M = m_b + m_m(0.23)## where ##m_b## is the mass of...

Hi, I need to transfer electricity to components that are rotating on a shaft but the power source is stationary with respect to the rotating shaft. the electricity is AC. So I had an idea of a rotating capacitor , two round plates , one stationary then a stationary dielectric attached to the...