What is Spinning: Definition and 579 Discussions

I got the opportunity a while ago to play around with a magnet floating above a superconductor cooled with liquid Nitrogen. The magnet was a little cube, and I spun it with a pair of tweezers. I was surprised at how quickly it stopped spinning, it seemed to stop much quicker than could be...

This button has fixed ends and the string is twirled and on the fixed ends there is hanging masses. I have found out that if string twirls are constant, the hanging mass is directly proportional to angular velocity squared. But I want to understand how that is derived. Could anyone please help...

We have a cylindrical water tank that spins over its axis of symmetry with constant angular velocity ω. Here's a diagram: We wish to find: 1 - The tangential and radial components of the velocity of the water as it leaves the tank. 2 - The radius r reached by the water. I'm not sure at all...

The subject of the thread summarizes my question: Could the accelerating expansion be explained by a "spinning" universe?

I'm trying to understand electron spin. I understand that if you try to explain the intrinsic angular momentum of an electron, you end up with the surface spinning several times the speed of light. However, calculations always seem to be done classically. Shouldn't it be done relatavistically...

How to find the angular speed, on which a spinning hollow cylindrical body breaks due to inertial stress(force)? I found 2 sources(http://www.roymech.co.uk/Useful_Tables/Cams_Springs/Flywheels.html (last 2 equations) ...

we all know that particles do spin. But my question is why it does so why do they spin? what will happen if they stop spinning? what makes the particle to do so?

Homework Statement A ball A is rotating on a table with an angular velocity ω about its vertical axis. An identical ball B collides with the ball A elastically. After collision the ball A starts sliding over the table. The coefficient of friction is µ. Find: 1) the angle α between the angular...

I need a 12v DC with appropriate torque. In my design, the axle of the motor would be pointed straight in the air and I want to affix a wheel to it and have the wheel spin flat, sort of like a pottery wheel sort of design. I know what the wheel is made of, its dimensions and approximate weight...

I would like to simulate a simplified version of this phenomenon: where I will assume that the viscosity is zero and the liquid can therefore swirl around "laminarly" forever according to some velocity profile that I specify. How can I calculate the shape of the surface, at least in this...

Homework Statement Spin 340 gram mass at the end of a 72 cm string in a horizontal circle around head 2.5 rev/s. Calculate tension Homework EquationsThe Attempt at a Solution I know tension might be equal to mass times centripetal acceleration, but I’m not sure

Homework Statement 1m diameter solid disc spinning at 10 rpms with a subsequent .5m diameter solid disc being driven by the 1m sokid disc. Homework Equations Not sure there is one for my particular situation. The Attempt at a Solution Just using the torque is equal to force times distance...

I am looking for an application to see how much force is needed to start a tire spinning to compare different sizes and weights of different brands of tires. This is to help give an idea of stress on a transmission. I have searched an hour hear as well as Google looking for a formula or...

The ball is given no initial horizontal velocity. It is however given an initial angular velocity of 76 rad/s and allowed to drop vertically from a height of 0.835m. Right after the ball bounces its vertical velocity is 3.1m/s upwards and its forward horizontal velocity is 1.838m/s and the ball...

Let's say that we have a bicycle wheel with radius $R = 25 cm$ and mass $m = 1 kg$. We spin the wheel in air so, that the tread is moving at the speed of $v_o = 50 km / h$. Then, we let it roll on asphalt, given the coefficient of static friction: $f_s = 0.9$ and kinetic friction: $f_k = 0.7$...

Theoretically, how fast in RPM can a circular sheet of graphene of radius 1 m spin without tearing apart?

The basic concept is to have your space probe(s) - likely nanocraft [1] on a spinning object in space which allows you to preserve the momentum you give it while accelerating it faster. Then once you are at a speed you can simply release the nanocraft in the direction you want it to go in. More...

Homework Statement Homework Equations The Attempt at a Solution The moment of inertia before collapse is for each rod: BEFORE COLLAPSE:[/B] Ib = ∫(L2 + x2) dm = m/L ∫(L2 + x2) dx = 4/3 * m * L2 We have 8 of these plus the inertia of the mechanism, giving a total I, It = 8 * Ib + Ik =...

Homework Statement Hi I'm having trouble with a question that's asking me to calculate the precession rate for a spinning top. The trouble that I'm having is that I don't understand how the angular momentum points along the axis of the spinning top (picture attached). When I use the formula...

Homework Statement This is a practice olympiad problem A light rod with length l is hinged in such a way that the hinge folds in one plane only. The hinge is spun with angular speed ω around a vertical axis. A small ball is fixed to the other end of the rod. (a) Find the angular speeds for...

Homework Statement You spin a 1.20 kg mass at the end of a 1.10 m string. The tangential velocity is 13 m/s. What is the tension in the string? Homework Equations x = angle string makes to the vertical L = string length r = L*sin(x) T*cos(x) = mg (because the sum of the vertical forces has...

Is it possible to spin a tiny spacecraft to near c speeds, and then have it eject from the object it's spinning on into space? I came with this idea after seeing the Starshot project that involved lasers and thought there might be a better way. What are your thoughts on this? Thanks

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...

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 [/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...

Hi, I am a research student, working on rotary jet spinning. while spinning, nanofibers are formed but it's not attached properly to the collector. It became like a spider web. You guys have any idea why it became like that?

A person standing on a stationary friction-less turntable spins a bicycle wheel with the rotation axis of the wheel in the horizontal direction, thus the initial angular momentum is in the horizontal direction (x - axis), say to the right. Now suddenly the person turns the axis of rotation of...

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...

How can I calculate the moment of inertia of a spinning top with charge Q submerged in an electromagnetic field? I've already calculated it for the case with no charge, but I don't know how to do this.

Hello, This is not a home work question but this seems to be the most appropriate spot to post this. I am trying to design a top that will spin for as long as possible. (Google "spinning top" if you're not sure what I a mean by a top) . I've been experimenting with different materials and top...

So I've just started reading into how gyroscopes work and I've hit a wall. Previously I thought that the upwards angular momentum kept the spinning object up straight, but why does it do the same if it's spinning clockwise too even though the angular momentum would be pointing down? Does the...

Homework Statement Homework EquationsThe Attempt at a Solution I know we can solve it by letting x=acos(\omega t)+acos(\theta+\omega t)\\ y=asin(\omega t)+asin(\theta +\omega t) and put their derivatives into the Lagrangian. But, I want to check the other points of view whether it is wrong...

Does anyone have formulae to calculate the number of turns required on a coil to produce 10V at approx 5W. I wish to have a coil spinning on a 16" diameter former in a 0.25 gauss magnetic field at a minimum of 2.2Hz. I need to be able to work out the size of coil and number of turns to produce...

This is a just for fun question. I saw the movie "Contact" and they built a machine that generated gravity by spinning rapidly. I assume this comes form general relativity. Is this correct? My question then is this. Is there a simple formula that can be used in which something moving in an orbit...

Let's assume there is a device that can hold fresh meat in a stationary position, and this device can spin at relatively high speeds. Would this allow fresh meat to last longer without freezing?

Homework Statement A mass ##m## whirls around on a string which passes through a ring. Given that gravity is not present and initially the mass is at a distance ##r_0## from the center and is revolving at angular velocity ##\omega_0##. The string is pulled with constant velocity ##V## starting...

Homework Statement Consider a rapidly rotating asteroid with an albedo (reflectivity) averaged over the solar spectrum of 0.05 that orbits around a 3 solar mass star that has the same surface temperature as the Sun. The asteroid’s orbit has a semi-major axis of 15 AU. What is its equilibrium...

Hi all, "When the top end of the Slinky is dropped, the information of the tension change must propagate to the bottom end before both sides begin to fall; the top of an extended Slinky will drop while the bottom initially remains in its original position, compressing the spring.[12] This...

Homework Statement Hello! I am trying to solve the exercise, but I don't see my mistakes - I can't come up with a correct answer. The exercise from the begging of trigonometry, so it has to be solved using concepts of a speed and angular velocity. A yo-yo which is 2.25 inches in diameter...

Homework Statement A 45 RPM record is a disk with a wide hole in the center. The mass of such record is 45g. It is 7 inches in diameter, and the hole in the center has a 1.5 inch diameter. (Sorry for the odd units, this was the way it was given). Find the moment of inertia of the 45 RPM...

This is the experiment I am a bit confused about this part: There is a torque on the wheel from its own weight. That's the τ on the picture. In this perspective, τ points at the bottom of the page. I understand that that torque changes angular momentum of the wheel and the wheel starts...

When I googled it, I wasn't satisfied with the answers from various sites...some sites like universetoday.com gave me a glimpse but it was totally theoretical and based on assumption. Also I would like to know why some planets have retrograde rotation; what might have caused them to and why do...

Homework Statement A 5kg ball is swung in a circle of radius .5 meters at a constant speed of 2 meters per second, how much work does the centripetal force do as the ball does once in a circle?If the ball were pushed the same distance as the circumference of the circle with a force equivalent...

Homework Statement In an effort to rev up his class, Mr. H does a demonstration with a bucket of water tied to a 1.3-meter long string. The bucket and water have a mass of 1.8 kg. Mr. H whirls the bucket in a vertical circle such that it has a speed of 3.9 m/s at the top of the loop and 6.4 m/s...

Homework Statement why does the spinning of wheels move a car? Homework EquationsThe Attempt at a Solution The wheels spin backwards pushing on the road, friction opposes this spinning motion. But why does this result in the car moving forward? friction can only increase to be equal and...

Ok now I have a strange question. The Earth is spinning continuously at a considerable speed. So if the Earth stopped spinning everything would be thrown by its momentum. But what would happen if for a split second you were no longer caught up in the Earths momentum. For example you are...

Homework Statement I need to show that a particle suspended on a spinning liquid (which is spinning with constant angular velocity) describes a spiral . (I need to solve this without using Lagrangian-Hamiltonian formalism)Homework Equations [/B] Weight and Bouyant forceThe Attempt at a...

Homework Statement The shows an arrangement of 15 identical disks that have been glued together in a rod-like shape of length L = 1.0000 m and (total) mass M = 100.0 mg. The disks are uniform, and the disk arrangement can rotate about a perpendicular axis through its central disk at point O...

Homework Statement A uniform thin circular rubber band of mass M and spring constant k has an original radius R. Now it is tossed into the air. Assume it remains circular when stabilized in air and rotates at angular speed ω about its center uniformly. Derive an expression for the new radius...

Look at this email I received from a company called ;Wisegeek' they send out interesting news items each day .. "If you spin a clean, new Lincoln penny, it will fall tails-side up about eight times out of 10. Forget what you know about statistical probability. If Persi Diaconis and researchers...