The Acceleration of a Sliding Collar on a Shaft

[eomama]

Homework Statement

For the mechanism shown, determine the speed and magnitude of the acceleration of collar C in terms of b, θ, θ-dot, and θ-dot-dot.

Check the attached file for the diagram.

We are given the length b and angle θ.

Homework Equations

ΣF=ma

The Attempt at a Solution

I started conceptualizing this problem right now. However, I don't even know where to start. The mechanism moves in such a way that θ 'closes' to 0 (since the whole thing falls). But how would I go about describing that in terms of 'b' ? It'd be dope to get some help/hints :) I'll post my work as the discussion develops. Thank you :)

 

[BvU]

Hello Ernesto,

"Don't know where to start" doesn't pass the PF guidelines
I'll get chastized for answering anyway instead of pressing the 'report' button .

What coordinate system would be the most convenient ?
How do you express the position of C in terms of $b$ and $\theta$ ?