Kinematics using vector analysis

[yugeci]

Homework Statement

Homework Equations

Va = Vb + Va/b
Va = Vb + (wab x ra/b)

The Attempt at a Solution

OK so here is part of my solution:

My velocity for B is correct according to the book. But I'm confused about D. The only problem here is that the velocity of D only has an i component, no j component. How do we know that and why is that? Also, how come the velocity of D isn't zero since it's a fixed point?

 

[Stephen Tashi]

Why do you think that D is a fixed point? At the time shown, D is at the end of CD and must move along the circle with center C since CD pivots about C. At the time shown, CD is vertical so the tangent vector to the circle is horizontal at that time.