Precession: A picture using only forces

In summary, the conversation discusses the phenomenon of precession in a spinning top and the forces involved in this motion. The direction of precession is explained using torque and vector calculations, but is not intuitive without this math. The conversation also explores a microscopic model of a spinning top and the forces acting on it, including gravity and centripetal force. However, the forces that keep the center of the top at a certain distance from the tip are not fully understood. A suggested resource for further understanding is a discussion of analyzing precession in Feynman's wobbling plate.
  • #1
greypilgrim
506
36
Hi,

If the axis of a spinning top isn't vertical, it starts to precess. I'm perfectly familiar with the explanation using torque, angular velocity and momentum vectors, then the direction of the precession comes out just by taking a vector product.

However, to me it's absolutely not intuitive without that math, especially the direction of the precession. I'm trying to use a "microscopic" picture with the top modeled as a ring consisting of many small masses on which only act forces (and no torque). So far I haven't been successful with this picture to produce a net force pointing in the direction of precession.

I'm not quite sure what forces I need to consider. There is gravity of course and a centripetal force to keep the masses on the ring. The sum of the centripetal forces on all the particles on the ring cancels. However there are also forces that keep the center of the ring at the same distance from the tip and the plane of the ring perpendicular to the line from the center to the tip, but I don't know how to deal with those forces.

Any ideas?
 
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  • #3
Another resource which you may find interesting is a sort of 'walkthrough' of how to analyze Feynman's famous wobbling plate from the point of view of forces. However, this problem involves free precession (not torque induced precession) and so is not exactly what you asked about.
 

What is precession?

Precession is the phenomenon where the axis of rotation of a spinning object changes direction over time due to external forces acting on it.

How does precession occur?

Precession occurs when a torque is applied to an object that is spinning. This torque causes the axis of rotation to change direction, resulting in precession.

What are some examples of precession?

One common example of precession is the spinning of a top. Another example is the precession of the Earth's axis, which causes the change of seasons.

What factors affect the precession of an object?

The magnitude and direction of the torque, as well as the angular momentum of the spinning object, are all factors that can affect the precession of an object.

Can precession be used for practical applications?

Yes, precession has various practical applications in fields such as navigation, astronomy, and engineering. For example, gyroscopes use precession to maintain stability and orientation in aircraft and ships.

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