# Homework Help: Determining the precession radius

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1. Nov 4, 2018

### Raihan amin

1. The problem statement, all variables and given/known data
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. Relevant equations.
Angular momentom L=IW
Again L=mυR and

τ=δL/δt

3. The attempt at a solution
I figure out the torque τ and the change of angular momentum .then i find the gyroscopic relationship W=mgr/Iω
Thanks.

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Last edited: Nov 4, 2018
2. Nov 9, 2018 at 6:00 PM

### PF_Help_Bot

Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.

3. Nov 10, 2018 at 7:59 AM

### kuruman

Do you really mean to say this? The COM is a point; an axis cannot be perpendicular to it but can only pass through it. It would help if you posted a drawing showing $\vec \omega$ as a straight arrow to clarify the spin axis. Could it be that the spinning stick is to be treated as a spinning top precessing in the Earth's gravitational field? In that case one end must rest on a horizontal plane and the stick must have a non-zero moment of inertia about its axis.