Spinning Definition and 581 Threads

Hello Forum, I have been reading a book, the Fabric of the Cosmos, by Brian Greene. It talks about Newton investigating the behavior of water in spinning bucket... Zero motion (at rest) and uniform motion (constant velocity) are two types of motion that cannot be distinguished: we cannot...

Everyone has seen a spinning top in action, and maybe some of you have also seen how they're able to stabilize completely like shown in the attached picture. I do get that they're hard to stop spinning because of conservation of angular momentum, but that they should be able to stabilize just...

So I get that conservation of angular momentum makes a spinning top stable. Same mechanism behind gyroscopes. When you first spin a top, there's a lot of wobble (precession), but it quickly dissipates. Why does this happen? The lack of wobbling must be a lower energy state if it is reached...

Homework Statement An axis-symmetric satellite is freely spinning in the space. The moments of inertia and the angular velocity at t=0 are as follows: Ix=200kgm2 Iy=Iz=100kgm2 wx=10rad/sec wy=1rad/sec wz=0 (a) Calculate the angular momentum of the satellite (b) What is the nutation...

Homework Statement To simulate gravity, a circular space station with a radius of 150 m is rotated so that astronauts standing on the inner surface move at 30 m/s. If the 75 kg astronaut stands on a bathroom scale what reading will it give? (assume the scale is calibrated in Newtons)...

Homework Statement The Hubble Space Telescope is stabilized to within an angle of about 2 millionths of a degree by means of a series of gyroscopes that spin at 1.92×104 . Although the structure of these gyroscopes is actually quite complex, we can model each of the gyroscopes as a thin-walled...

Homework Statement A weather vane sits quietly on the roof of a barn on a calm winter's day. It has a length of x, is pole-shaped with mass M, and rotates frictionlessly about its center. But just now it is still. Suddenly Justin throws a snowball of mass m at speed v that hits it a...

Homework Statement A puck, mass m, on the end of a (thin, light) string rotates in a circle of radius r_0 at a speed v_0 on a frictionless table. The radius of the circle is slowly reduced from its initial value by pulling the string through a hole in the table. A. Hence write down an...

I was watching a physics lecture and the instructor made the statement that "for a given mass, decreasing the diameter of the body makes it harder to spin up". In one way this makes sense, as with a smaller diameter one has a shorter torque arm to work with... however, I seem to recall from my...

A black hole is a singularity at which the curvature of spacetime becomes infinite. I understand that when a star collapses it can have a net angular momentum, but when it collapses down to a 0-dimensional singularity, what does it mean for that to have angular momentum? Thanks

Hello, Does a spinning mass warp space time differently than a non rotating mass? Is the generated gravitational field different, and have there been any experiments to actually verify or falsify this?

Hi, Does a spinning mass affect the spatial/time fabric differently than a non rotating mass?

A solid uniform disk of mass 19.0 kg and radius 70.0 cm (.7 m) 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. The string is being pulled. When the disk has...

If someone(s) would be so kind, I have some complicated curiosities about spinning superconductors. This is not homework. What types of materials can a spinning superconductor lift? Does it only work against gravity, or can it work in any direction? Does it have to be cooled? How much...

1. What happens when two spinning disks collide? Suppose you have two flat, thin disks with uniformly distributed masses m1 and m2, moving at angular velocities ω1 and ω2. the two objects are brought together edge to edge, ie they collide. obviously as a result of this collision, the objects'...

Hello everyone, this is my first post here so I hope I don't commit any physicsforums faux pas in this! I have a curiousity. If you take a rugby ball or any other prolate ellipsoid and give it a good spin, it will rise up onto it's end. I wonder if any of you guys could clear up exactly why...

Homework Statement In an old record player, the flat round vinyl disc (record) is placed on a turntable which spins around. Once it gets going around and around, it moves so that the number of revolutions it makes per minute is constant (33 and 1/3). An insect settles on the edge of the...

Homework Statement Carousel is spinning when w = 1.4rad / s. on the carousel there is a given body. Static friction between the carousel with the body is 0.2 What is the radius that you can put the body on the carousel that the body won't slip? Homework Equations The...

Homework Statement http://imageshack.us/f/41/physicsc.png/ My professor gave the following hints: Write down what you know about how r (position of mass from hole) varies with time. Then write Newton's 2nd law in polar coordinates. For part (a), the differential equation that you are looking...

I'm going to simplify this situation so I can hopefully better understand what is going on. A bowling ball is given a certain initial rotational velocity and a certain initial linear velocity when thrown down a bowling lane. If everything needed to solve this problem is given, such as radius of...

Does spinning a massive sphere at high speed would somehow create extra gravity pull (or some sort of phenomenon perceived as such) added to it's initial gravity force (rest state gravity/not spinning state gravity)? I came to the assumption that accelerating the speed of an object would...

A magnet that won't stop spinning?? what happens if a horseshoe magnet is fixed to a a coil such that there is a constant field through the coil?? The initial torque due to the field will spin the coil,but since the magnet is connected to the coil,it will keep sending a field through the coil...

Spinning magnetic field through a coil-can this propel engines?? Magnetic field through a coil produces torque in the coil. Suppose we have a coil.The set up is such that the magnetic field passes through the coil.Now,if we spin the magnetic field along with the coil,the coil will keep...

Hello. This question has kept me up all night: What mechanism would keep a wheel spinning using as little electrical energy as possible? Let's say we have a toy car (could be anything that involves a wheel) that is already in motion and moving with a constant velocity. What would you build...

If a circular disk rotates about its centre, what will happen to its geometry. Since a spinning disk has velocity gradients, different regions of the disk must contract by different proportions. For example, a uniformly moving body undergoes length contraction and its new geometry is easily...

How would I go about calculating the resultant forces / torques on a system if it's previously spinning at a constant angular velocity, but then an external torque is applied to it? I would like to use this for some very basic analysis of a custom gear box used in a robotic joint. We attach...

A while back I piggy-backed onto another thread (and then withdrew it as being out of place) an example of a system possibly violating the conservation of energy and momentum (angular momentum directly) - a spinning hollow right circular cylinder placed under frictionless axial compression. Many...

If You are suddenly teleported from the equator to the north pole. How fast and which way will you be spinning relative to your surroundings?

Don't know if anyone seen it, it's out today in a journal: http://www.msnbc.msn.com/id/42787604/ns/technology_and_science-space/ Sounds interesting, one of the first to catch my attention for a while (perhaps I just like big numbers...).

Okay, so let's say there is an object with a shaft connected to it. The shaft rotationally spins the object. On the top and bottom of the object are N magnetic fields. Not touching the object or shaft are magnets attached to a solid surface with N fields. Those are within distance to act on...

1. A light, hollow cone is filled with sand set spinning about a vertical axis through its apex on a frictionless bearing. Sand is allowed to drain slowly through a hole in the apex. Calculate the fractional change in angular velocity when the sand level has fallen to half its original value...

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...

All the texts and sites I can find discuss the rotational dynamics of pure rotation, pure translation, or a combination of an object rolling without slipping. I am trying to resolve some rotational dynamics regarding a spinning object that is moving linearly.. such as a planet in space or a tiny...

This is a problem from Kibble Classical Mechanics, so it may be harder than it looks. Homework Statement 10. A particle of mass m is attached to the end of a light string of length L. The other end of the string is passed through a small hole and is slowly pulled through it. Gravity is...

Homework Statement An electric dipole consists of 1.0 g spheres charged to +(-) 2.0 nC at the ends of a 10-cm-long massless rod. The dipole rotates on a frictionless pivot at it's center. The dipole is held perpendicular to a uniform electric field with field strength 1000 V/m, then released...

This is not a homework question but could not find a better place to post it. Why doesn't a spinning top fall over instantly? Also why does it fall later? What makes spinning so special? Are the answers different for top spinning with its axis fixed and the top with its axis moving conically...

When you release a top with high speed, it rises for an instant. Why is this? I've also seen magnets spinning madly when suspended above superconductors. Are these observations related and is there an explanation for this? Many Thanks, :)

I understand that an electron can gain and lose energy, but before this, the electron is spinning around the nucleus of an atom. Since motion requires energy, what is the energy that keeps the electron spinning. Further- since there is loss in every system- if no energy is applied or taken...

I was watching a youtube video about a magnetized spinning top, floating over a magnetic bottom. I was wondering why this only works when the spinning top is spinning? Can't a magnetic field be stable? Would it still work with a stillstanding top, and the magnetic bottom rotating? If you...

What effect does rotation have on a sphere moving through a fluid (liguid or gas) when traveling along the axis of rotation? The simplest being an up or down motion.

Faraday's law says that an induced voltage across a conductor is directly proportional to the rate of change of magnetic flux through the conductor, but I am having trouble getting my head round how it works in this situation. Imagine a perfectly circular thin copper disc, and that this disc...

OK, so let's say there was a ring around Earth (imagine the video game Halo). Extending from the Earth are huge cables that greet the ring (space elevator). This ring surrounding Earth would have magnets lining the entire structure. The cables would have wire wrapped end to end so that was the...

OK, so this is what I read: << Moderator added link for attrubution >> http://education.jlab.org/qa/gravity_01.html Here's what I'm confused about. Let's say there is an object that weighs a ton on Earth's surface and a replica of that object in orbit at the distance where it weighs...

Hey guys, this is not so much a homework question as it is a thought that I'm pondering. Homework Statement If we have a dancer that is spinning on her toes (wherein she is wearing a metal shoe with a very very very sharp tip) with her CG located above that tip, what is the contact...

Trying to analyze all the dynamics of gyroscopic type motion. Assume the Z axis is vertical (which the wheel precesses about) Have a spinning bicyle wheel, that is held up via string on one end, the biycle wheel begins to precess about the vertical axes via torque induced from gravity...

I'm beginning to read about spinning tops and in particular, the Lagrange solutions for these tops. 1) When I solve the equations of motion for these tops (acting under gravity), the resultant motion is either looping or somewhat of a sinusoidal motion (see video...

I searched through the forums and couldn't find a topic or answer, so I will pose it (possibly again). I can work through deriving the equations of motion (either through Euler-Lagrange methods or Hamilton methods) for the spinning book problem and it is obvious that there *is* an unstable axis...

spinning hoop--what if it were a cycloid? This wasn't an assigned problem, but something that came up in discussion... Homework Statement The original problem was to show that a hoop spinning about a fixed axis in a horizontal plane will induce a bead into oscillations similar to a...

Homework Statement Two gerbils run in place with a linear speed of 0.55m/s on an exercise wheel that is shaped like a hoop. Find the angular momentum of the system if each gerbil has a mass of 0.22kg and the exercise wheel has a radius of 6.5cm and a mass of 5.0g. Homework Equations...

Suppose you make a big horizontal wheel, put markings at equal distances on the edge and also on the floor just outside the wheel. Now let the wheel spin at relativistic speeds. If you are standing next to the wheel, the markings on the wheel will be closer together (because they are moving)...