Angular velocity and acceleration of a block moving at constant velocity

[skp123]

Homework Statement

The block moves to the left with a constant velocity v.

a)determine the distance x as a function of Q .
b)determine the Angular velocity as a function of Q
c)determine the Angular acceleration as a function of Qhttp://img98.imageshack.us/img98/3691/16293179.jpg

Homework Equations

The Attempt at a Solution

Here is how i find the distance x. tagQ=a/x -> x=a/tagQ .
Can anybody help me a little bit how to find b). Is it enough just to find the 1-st and 2-nd derivative of x in order to find velocity and acceleration ?

 

[skp123]

Can anyone give me a little hint ?