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# Questions tagged [precession]

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367 views

### How much force is required to break precession?

Gravity, in this diagram, provides a downward force creating a torque that causes the wheel to precess around the chain. This is cool but counter intuitive, and I am wondering what force is needed to ...
1 vote
271 views

### Quick question regarding Larmor precession and bar magnets

So I was just reading a bit about magnetic dipole moments, Larmor precession, angular momentum etc., but there was one little thing that was bothering me. As far as I know, any angular momentum will ...
708 views

### Feynman Lectures: 20–3 The gyroscope

In the The Feynman Lectures on Physics, Volume I, Chapter 20, Section 3,The Gyroscope found here, Feynman wrote We note that when the wheel is precessing, the particles that are going around the ...
1 vote
70 views

### Is Energy conserved in a spinning top?

When we spin a top (give it kinetic energy $K_0$) and place it on a table, it starts precessing around the vertical axis. Is the total energy of the spinning and precessing top equal to the initial ...
1 vote
425 views

### NMR: Why does 180 degree pulse turn around direction of lamor precession?

In descriptions of the spin echo measurement sequence, it says first a $90°$ pulse turns the magnetization sum vector into the transversal plane where it rotates with the Larmor frequency spins of ...
1 vote
458 views

### Gyroscope precession and Euler equations

I've been trying for so long to solve this problem, but the solution I have found isn't the one I expected. Basically, I have to solve Euler's equations for a gyroscope with a weigth at a distance d. ...
78 views

### Is the Laplace-Runge-Lenz vector applicable for test particle motion around black holes?

In classical mechanics , the Laplace-Runge-Lenz (LRL) vector is a characteristic feature of the Kepler problem. This enables a very simple discussion of the properties of the orbit for the problem. It ...
250 views

### Weird rotational motion of a heavy thick disc

I and my friend noticed a strange behaviour of a rotating disc (or a cylinder) and we don't know how is that happening. This is the video. Actually what is happening in the video is that the disc ...
82 views

### Why does the gyroscopic precession of a spin-stabilized bullet cause drift in the same direction as the spin?

I am trying to understand the physics behind the gyroscopic phenomenon called spin drift. Spin drift occurs to bullets that are spin-stabilized over the course of their flight. Spin drift starts with ...
515 views

### Precession of Angular momentum of Symmetric Top

For a torque free symmetric top, is the angular momentum in body fixed coordinates in same direction as instantaneous axis of rotation? I know that instantaneous axis of rotation precesses about ...
1 vote
654 views

### Nutation frequency for a weighted gyroscope

So, I've been led to believe that the frequency of nutation of a gyroscope can be calculated using the formula In which the I's are the moments of inertia around the principal axes and omega-3 is the ...
379 views

### Do protons and electrons actually precess?

I know that protons and electrons do not actually spin, although they have the property of spin. I was learning about MRI. I was introduced to the idea that you have the spin of the proton in the ...
1 vote
33 views

### How to calculate the distance of Mercury's perihelion shift in meters? [closed]

Since the shift in mercury's perihelion shift is 2.88E-5 degrees and mercury's altitude above the Sun at its perihelion is 46001200000 meters, can I use the formula for an isosceles triangle to ...
69 views

### How to obtain Mercury Precession equation $\frac{d^2u}{d\theta^2}+u=a$?

Let $r=R(t)$ and $\theta=\Theta(t)$ describe the orbit of the planet. Define $$u(\theta)\equiv\frac{\bar r}{R[\Theta^{-1}(\theta)]}$$ where $\bar r=5.83\times 10^{12}$ cm be the mean value of the ...
52 views

### Response of a loop of current vs. a rigidly rotating charged ring to a magnetic field

In a uniform magnetic field, a loop of current on a wire will feel a torque that makes the magnetic moment of the loop align with the field direction. But for a rigidly rotating ring of charge, its ...
400 views

### Larmor Frequency for Spin Transition

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/larmor.html Consider the process of Larmor precession of the magnetic moment associated with the spin angular momentum of an electron inside a ...
52 views

### How can I conceptually interpret spin precession?

In Sakurai section 2.1, he works through an example of spin precession where we come to the conclusion that, when working in the z-basis and applying a magnetic field in the z-direction, the spin ...
574 views

### Infinite Larmor precession

Say an isolated electron (meaning it's not part of an atom) is at rest and we turn on a homogeneous magnetic field around it. The electrons' spin undergoes the Larmor precession (except in the case ...
1 vote
160 views

### Regarding nuclear magnetic resonance

In NMR experiment we provide an external radio frequency signal which will induce transition of nuclear spins to higher states,and then it returns to ground state precessing around the magnetic field ...
326 views

### Precession of perihelion of Mercury?

I have a few questions about precession of Mercury and GR corrections. Feel free to any that you can: GR is used to correct precession caused by Sun on Mercury by time dilation and length contraction....
15k views

### Direction of torque precession of a spinning wheel

Consider a spinning wheel, which is held up by one end of it's axis like this: To explain why the change of angular momentum is directed as shown in the figure above, one usually says that there is ...
1 vote
3k views

### Torque and angular acceleration with bicycle wheel

This might be a simple problem for many of you. However, please help me understand it too. I have been looking trough a lot of materials online, and I still have the following questions, that would ...
119 views

### Pencil doesn't act as a spinning top

If one spins a spinning top, it'll stay up for a while before falling down. However, if one spins a pencil, it falls down immediately, just like if you didn't spin it at all. My question is why there ...
280 views

### Can someone please explain Gyroscopic precession?

So I watched this video It is a fairly popular one by veritasium, and one that confused me. I was wondering if someone can cover the physics behind this in a intutitive and easy to understand manner. ...
200 views

### Gyroscopic bicycle wheel - forces on the wheel only

This is a standard problem in university physics, which I studied at university in depth. With higher concepts like angular momentum, it is fairly straightforward to explain the motion. However, one ...
49 views

### Can orbiting point masses precess?

In a recent Science News, it mentioned two orbiting black holes (which later combined) were precessing; i.e. their motion did not remain in a stable plane, but rather the plane itself was changing. ...
23 views

### Is the diameter of earth's north pole similar to the south? (Think axis of rotation+ axis of precession)

Earth is an oblate spheroid, not a sphere, since it's rotation around the axis causes it to bulge along the equator. Is it teally a symetric oblate spheroid though, or also not even that? To explain: ...
2k views

### Does the length of the sidereal day vary systematically?

I'm confused about some properties of the sidereal day, in particular whether its duration varies systematically over the course of the year.1 It seems to me that that must be the case, but the ...
31 views

### NMR without static magnetic field

NMR is usually conducted by first aligning nuclei to a strong, constant magnetic field, so that you can apply RF radiation with a magnetic component directly perpendicular to the constant field. ...
10k views

### How do you calculate the anomalous precession of Mercury?

One of the three classic tests of general relativity is the calculation of the precession of the perihelion of Mercury's orbit. This precession rate had been precisely measured using data collected ...
93k views

### What did general relativity clarify about Mercury?

I frequently hear that Kepler, using his equations of orbital motion, could predict the orbits of all the planets to a high degree of accuracy -- except Mercury. I've heard that mercury's motion ...
390 views

### Understanding work with rotational momentum/moment of inertia

Apologies for the basic question but between the vectors and the spinning, I'm getting confused. If I have a wheel with moment of inertia $I$ spinning at some rate $\vec\omega$ around an axis, what ...
1 vote
53 views

### Geodetic Precession of a Gyroscope in Hartle's GR Book

In 14.3, Hartle deduces the geodetic precession angle per orbit of a gyroscope in Schwarzschild geometry. Immediately after eq.(14.18), the book reasons that the angle deduced is physically measured ...
132 views

### Is it right assume the greater the precession of a type of particle in the same magnetic field the slower the particle spin?

Is it right that the greater the Larmor frequency of a particle measured for same magnetic field applied the slower a particle spin is? I read these articles http://hyperphysics.phy-astr.gsu.edu/hbase/...
93 views

### How can precession produce a torque in the direction of precession when it has no angular momentum?

I this video, an 8 lb gyro on a rod supported at one end is spun up to several thousand rpm, and an assist is use to get the axis nearly horizontal. A small stick is used to nearly instantly stop the ...
160 views

### Proton spin precession and alignment to magnetic field in NMR

Precession due to magnetic field occurs when the magnetic moment of a small coil is proportional to its angular momentum ($\vec{m}=g\vec{L}$). This is due to Euler momentum equation, which for such a ...
1 vote
228 views

### Confusion about the Spinning Top

Consider the following symmetric spinning top with a fixed point on the horizontal surface. I have two questions concerning its motion: let $\underline{\Omega}$ denote the precession angular ...
75 views

### Direction of angular velocity vector VS angular momentum vector

I understand that angular velocity and angular momentum velocities don’t need to be parallel to each other. However, I’m confused what these vectors even represent. So I have 3 questions about this: ...
1 vote
835 views

### How does precession affect angular momentum?

I have been studying Irodov's problem book. There are a lot of good problems that challenge conceptual knowledge, and so I have to ask somebody for a qualitative answer. I can best describe my ...
2k views

### What gives energy for precessional motion of gyroscope?

Let us suppose we have an ideal friction-less gyroscope and it is suddenly given an angular momentum, and left as in the figure. It will start precessional motion. Since there is no friction, the ...
25 views

### Is it possible to change the speed at which a wheel is freely spinning by moving only its axle?

Suppose we have a wheel spinning on a perfectly lubricated axle. Is it possible to change its angular velocity about that axle, by moving only the axle? Due to the wheel's symmetry about the axle's ...
40 views

### Non-swinging Foucault's pendulum

If there is a stationary pendulum, say at the North pole, neglecting torsion, etc. will it seem like spinning around its axis from the reference frame fixed to the Earth's surface. If so, will it ...
48 views

### Will the inner gimbal continue to rotate if no friction?

The picture shows a gyroscope with a rotating disk. Adding a force to the outer gimbal from a certain direction causes the inner gimbal (plus the disk with bearings) to rotate as well. When the force ...
112 views

### Resisting Precession of a Gyroscope

its known that if a torque is applied to a spinning gyro, the gyro will pitch. There's a lot physics on the pitch speed, but what is the torque to induce this pitching? ps. I am building a gyro ...
783 views

### How do I calculate Earth's axial precession in an idealized Sun-Earth system?

I am experimenting with an idealized two-body system based on the Sun-Earth system. I want to calculate how much Earth's axis precesses and nutates given the simplified setup. In my system, the orbit ...
1 vote
280 views

### Confusion with Thomas precession

Suppose an inertial frame $S^\prime$ is moving with a relative velocity $\textbf{v}=v\hat{n}$ w.r.t another intertial frame S with their axes parallel and $\hat{n}$ is an arbitrary direction. In that ...
65 views

### Equation to tell if precession will happen?

So I have an seen the equation to calculate precession but it breaks down at when there is not sufficient angular momentum, for example if an object is not spinning we divide by zero and the ...
92 views

### Does a precessing spin in constant magnetic field change the field somehow?

If an electron enters a magnetic field along the lines of the magnetic induction it spin starts to preccess. Suppose the field was made by a coil (toroid). What changes happen in the field - current - ...