Epicyclic motion and precession

AI Thread Summary
The discussion centers on the concepts of epicyclic motion and precession, specifically whether rotating while moving in a circular path constitutes precession. It is clarified that if a person is standing straight and rotating without moving forward or backward, there is no axial precession occurring. Precession typically involves a change in angular momentum, which does not happen in this scenario. The distinction between torque-induced precession and torque-free precession is noted, with emphasis on the fact that precession involves a wobble in the axis of rotation. Ultimately, the conclusion is that the friend's interpretation of precession is incorrect in this context.
warfreak131
Messages
186
Reaction score
0
Imagine I am standing but not moving forward/backward, but I am rotating my body about my own axis. Now imagine if I moved in a circular path as I was spinning on my own axis. Is this considered to be precessing (assuming the axis of rotations are always in the z direction)?

My friend says it is, but I disagree. Wouldn't I always have the same angular momentum? And torque induced precession requires a change in L? Now I know there is a torque-free precession, but I didn't quite understand it. Can someone clear this up?
 
Physics news on Phys.org
See http://en.wikipedia.org/wiki/Precession

If you are standing straight there is no axial precession; precession induces a wobble in the axis of a gyroscope.

So your friend is wrong - unless he means something else by the term precession.
 
  • Like
Likes 1 person

Thread '1:1 versus 2:1 Mechanical Advantage debate'

The rope is tied into the person (the load of 200 pounds) and the rope goes up from the person to a fixed pulley and back down to his hands. He hauls the rope to suspend himself in the air. What is the mechanical advantage of the system? The person will indeed only have to lift half of his body weight (roughly 100 pounds) because he now lessened the load by that same amount. This APPEARS to be a 2:1 because he can hold himself with half the force, but my question is: is that mechanical...
View full post »

Thread 'Average velocity as a weighted mean'

Hello everyone, Consider the problem in which a car is told to travel at 30 km/h for L kilometers and then at 60 km/h for another L kilometers. Next, you are asked to determine the average speed. My question is: although we know that the average speed in this case is the harmonic mean of the two speeds, is it also possible to state that the average speed over this 2L-kilometer stretch can be obtained as a weighted average of the two speeds? Best regards, DaTario
View full post »

Thread 'Newton's first law?'

Some physics textbook writer told me that Newton's first law applies only on bodies that feel no interactions at all. He said that if a body is on rest or moves in constant velocity, there is no external force acting on it. But I have heard another form of the law that says the net force acting on a body must be zero. This means there is interactions involved after all. So which one is correct?
View full post »

Similar threads

I Effects of External Torques on the Angular Momentum of Asymmetric Bodies
Replies
3
Views
1K
I PIGA: Pendulous Integrating Gyroscopic Accelerometer
Replies
0
Views
1K
Precession - why does the rotational axis change as L changes?
Replies
8
Views
2K
The order of Euler Angle rotations for a top
Replies
7
Views
2K
A Cause of upward motion of a nutating top
Replies
1
Views
1K
I Precession of a gyroscope in freefall
Replies
10
Views
3K
I I never fully understood gyroscopic precession - toppling gyroscopes
Replies
10
Views
386
I How to quantify gyroscopic precession torque?
Replies
34
Views
3K
Understanding Rigid Body Rotation: Principles and Observations
Replies
3
Views
1K
I Torque required to prevent precession
Replies
2
Views
1K

Hot Threads

Recent Insights

Back
Top