Read about precession | 23 Discussions | Page 1

  1. Raihan amin

    Determining the precession radius

    Homework Statement A stick of length 2L and of mass M spins with angular velocity ω around the axis perpendicular to the COM of the stick.It is rotating with making an angle Θ,with the axis parallel to Z axis.The COM has an initial velocity v=υ(to the y axis).Find it's precession radius R...
  2. J

    Position as function of time - satellite in elliptical orbit (spherical coordinates)

    I've been scratching my head over this for a while now. Seems pretty simple, but I just can't get anywhere! So, this is a problem out of pater & Lissauer's Planetary Sciences book (prob 2.10). Starts off by describing how Neptune was discovered by observing anomalies in Uranus's orbit...
  3. P

    I Free Precession animation - body frame to space frame

    I'm creating an animation of free precession of a cuboid in GeoGebra. The axis of rotation is not one of the principal axes (but does go through center of mass). Since it's much easier to find the angular velocity and L in the body frame, I defined the e1, e2 and e3 axes (as opposed to the...
  4. G

    Why is the Gödel Universe Rotating

    Homework Statement Consider the Godel Metric in spherical coordinates as on page 6 here; ds^2=4a^2\left[-dt^2+dr^2+dz^2-(\sinh^{4}(r)-\sinh^{2}(r))d\phi^2+2\sqrt{2}\sinh^{2}(r)dt d\phi)\right] This is a solution to Einstein's Equations if we have ##a=\frac{1}{2\sqrt{2\pi\rho}}## and ##\Lambda...
  5. J

    Angular momentum direction for a spinning top

    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...
  6. riveay

    I Euler angles in torque free precession of a symmetric top

    Is calculating the Euler angles analitically possible? I am trying to obtain the angles to transform the body-fixed reference frame to the inertial reference frame. I can get them without problems with numerical methods. But I would to validate them analitically, if possible. I followed the...
  7. JTC

    I Direct vs. Retrograde Precession

    (This is not about the motion of the planets.) If one takes a body in space (not outer space, necessarily) with only central forces, it may exhibit one of two types of precession: direct or retrograde. If the body is flat, the precession is retrograde: the spin and precession rates have...
  8. G

    I Mercury's precession due to other planets

    Hi. I'm interested in how physicists in the mid-19th century such as Urbain Le Verrier were able to compute the gravitational influences of the other planets on the apsidal precession of Mercury's orbit, finding that they can only explain about 531" (per century!), not the observed 574". This...
  9. E

    B Gyroscopic precession force diagram

    Hi, I've been learning about gyroscopic precession recently and I feel like I get it. I understand that when the flywheel of a gyroscope is spinning its angular moment plus the angular moment created by the torque from the force of gravity makes it turn. But I were thinking about the forces in a...
  10. T

    I Gyroscopic precession

    I was watching this and I get it that when you rotate the wheel, the torque due to its weight will cause it to revolve parallel to the ground instead of perpendicular to the ground. I know that the faster you spin the wheel, the less likely the lever from the wheel to the pivot will be slanted...
  11. Tazerfish

    I Can every shape precess like a top (toy)?

    The main question is in the title. 1.I have wondered if a regular pencil would precess and rotate stable for multiple seconds if spun fast enough. [Coins, plates, bowls and similarly shaped objects can rotate in a stable way for extended periods of time. And a lot of other household objects...
  12. S

    I Proof derivative of a vector following precession motion

    I do not get some points of this proof about the time derivative of a unit vector $\hat{u}$ (costant magnitude) which is following a precession motion. The picture is the following. I want to prove that $$\frac{d\hat{u}}{dt}=\vec{\Omega}\wedge \hat{u}.$$ I'm ok with almost all the proof...
  13. G

    Precession and weight

    Many of you might have seen veritasium's video on the "Anti-gravity wheel". Through one of the comments, I was introduced to the idea that the reason the apparatus is so easy to lift is because the energy to do so comes from the spin of the wheel, i.e. its rotation slows down as it is lifted and...
  14. G

    Translational approach to precession

    Hi. I'm trying to take a purely translational approach to precession (i.e. not using angular momentum and torque). I'm looking at a gyroscope that consists of four point masses on a cross and at a moment in time when one mass is at the topmost point (see sketch). I'm assuming a virtual...
  15. G

    What if I force a spinning wheel not to precede?

    Hi, If we apply a torque to a spinning wheel such that the torque vector lies in the plane of the wheel, it will precede around the axis perpendicular to the angular momentum and the torque. What happens if the wheel is mounted such that rotation around this axis is absolutely impossible and...
  16. jaketsi

    Thinking about 3D rotating

    Hi folks! First of all, English is not my native language so I hope there is not much misleading spelling mistakes, discrepancies and inaccuracy. I’m currently working with a hobby-project of a flying drone/UAV with two adjustable angled rotors. I’m able to make it fly more or less in a way...
  17. J

    Precession of angular momentum in vector model

    Hey everyone, I just made an account because I have a problem concerning angular momentum and precession. In the picture below you see the vectors l1 and l2 that make up total orbital angular momentum L precess around L. I can get my head around why that is the case. The same for s1 and s2...
  18. 24forChromium

    When a gyroscope precesses, what is pushing it along?

    This is the kind of gyroscope that I am talking about: Where did the kinetic energy of precession come from? The gyroscope's spinning angular inertia? If so, how does it transfer into the precession? Is a torque applied horizontally (along the x-y plane) when the system is under the effect of...
  19. V

    Precession of Mercury and period of rotation

    HI - we know that the orbit of mercury precesses (I hope I am using the right terminology here). Which basically means that the orbit seems to undergo some sort of rotation in the ecliptic plane. Does this also mean that the period of Mercury's orbit as seen from the earth is not uniform but...
  20. M

    Why is a gyroscope's precession fastest at 45 degrees?

    I did an experiment in which I varied the starting angle of elevation of a gyroscope. I noticed that at 45 degrees, the precessional period (amount of time to perform one spin) is the lowest, while at 0 degrees and 75 degrees, the precessional period is higher. If I plotted this on a graph, it...
  21. kmm

    Gyroscope precession energy

    I'm trying to think about gyroscope precession in terms of energy, and I'm a little confused. If you hold the spinning gyroscope at some tilt so that it doesn't precess, it will have energy associated with it's rotation. When you let it go, it will now have additional energy due to the...
  22. G

    Initial Gyroscopic Precession Using Forces

    I think I more or less understand how a gyroscope precesses--at least mathematically and in terms of torque/angular momentum. My question here is: how does the gyroscope start precessing in the first place? The external forces on the center of mass are entirely vertical. Given that Newton's...
  23. D

    Gyroscope: Calculating Torque

    I am a college student currently working on a physics project involving gyroscopes. Using the equation below (taken from Wikipedia), am I correct in assuming that dL/dt is the torque of the flywheel and that ω x L is the torque of the gyroscope around the axis of precession?
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