# Homework Help: Dynamics rotating disk, solve for r and theta magnitudes

1. Sep 15, 2010

### lax1113

1. The problem statement, all variables and given/known data
A screen clipping of the problem is here: http://img529.imageshack.us/img529/1738/dynamicsquestion2.jpg [Broken]

We have a circular disk that roates about its center, 0, with a constant angular velocity $$\omega$$ ($$\omega$$ = $$\dot{\theta}$$. The disk carries two spring-loaded plungers. The distance b, that each plunger protrudes from the rim of the disk varies according to b = bo * sin (2$$\Pi$$nt), where bo is the max protrusion (n is a constant of oscillation, t is time).
Determine the maximum magnitudes of the -r and -$$\theta$$ components of the acceleration of the ends of the plunger during their motion.

2. Relevant equations
Vt = d$$\hat{u}$$r/dt

at = $$\omega$$^2 (ro + sin (2$$\Pi$$nt)

3. The attempt at a solution
So with the At equation that is above, it is really obvious that the max r component of the acceleration will be when the trig portion is its max or 1. So this happens when t = n/4. We can substitute $$\dot{\theta}$$ in for omega, but I am not quite sure what it means by the maximum magnitude of the theta component.

Any hints would be appreciated, or if the direction I am headed in currently off.

thanks

Last edited by a moderator: May 4, 2017